,transcriber's ,notes3 ,text between underscores and equal signs represent text printed in italics and bold face respectively2 text represents superscript text2 #a represents #a with a bar above4 ,small capitals have been transcribed as ,,all ,,capitals4 ,more ,transcriber's ,notes may be found at the end of this text4 ,,irrigation ,,works ,by the ,same ,author ,,river ,,and ,,canal ,,engineering4 ,the ,characteristics of ,open ,flowing ,streams1 and the principles and methods to be followed in dealing with them4 #gb illustrations1 x #bbj pp41 #hvo 7#aiac74 #h_/f net4 ,,punjab ,,rivers ,,and ,,works4 ,second ,edition4 #dg illustrations1 viii #fd pp41 folio 7#aiab74 #h_/- net4 ,,hydraulics ,,with ,,working ,,tables4 ,second ,edition4 #afj illustrations1 xii #caa pp41 #hvo 7#aiaa74 #ab_/- net4 ,,the ,,suction ,,caused ,,by ,,ships4 ,explained in ,popular ,language4 #b plates1 #bf pp41 #hvo1 sewed 7#aiab74 #a_/- net4 ,e4 ,f4 ,n4 ,,spon1 ,,ltd41 ,,london ,illustration3 ,,bridge ,,on ,,an ,,indian ,,canal4 ,frontispiece4 ,,irrigation ,,works ,,the ,,principles ,,on ,,which ,,their ,,design ,,and ,,working ,,should ,,be ,,based1 ,,with ,,special ,,details ,,relating ,,to ,,indian ,,canals ,,and ,,some ,,proposed ,,improvements ,,by ,e4 ,s4 ,,bellasis1 ,m4,,inst4,c4,e4 ,,recently ,,superintending ,,engineer ,,in ,,the ,,irrigation ,,branch ,,of ,,the ,,public ,,works ,,department ,,of ,,india #cg ,illustrations ,illustration ,london ,e4 ,f4 ,n4 ,,spon1 ,,ltd41 #eg ,,haymarket1 ,s4,w4 ,new ,york ,,spon ,,chamberlain1 #abc ,,liberty ,,street #aiac ,,contents ,,page ,,preface vii ,,chapter ,i ,,introduction ,,article #a4 ,preliminary ,remarks #a #b4 ,general ,principles of ,canal ,design #b #c4 ,information concerning ,canals #aa #d4 ,losses of ,water #af #e4 ,duty of ,water #ba #f4 ,sketch of a ,project #bf ,,chapter ,,ii ,,the ,,designing ,,of ,a ,,canal #a4 ,headworks #cj #b4 ,the ,contour ,map #cf #c4 ,alignments and ,discharges #cg #d4 ,remarks on ,distributaries #de #e4 ,design of ,canal and ,branches #dg #f4 ,banks and ,roads #ec #g4 ,trial ,lines #eh #h4 ,final ,line and ,estimate #ei #i4 ,design of a ,distributary #fj #aj4 ,best ,system of ,distributaries #ga #aa4 ,outlets #gf #ab4 ,masonry ,works #hj #ac4 ,pitching #ij #ad4 ,miscellaneous ,items #ic ,,chapter ,,iii ,,the ,,working ,,of ,a ,,canal #a4 ,preliminary ,remarks #if #b4 ,gauges and ,regulators #ajc #c4 ,gauge ,readings and ,discharges #ajf #d4 ,registers of ,irrigation and ,outlets #aac #e4 ,distribution of ,supply #aah #f4 ,extensions and ,remodellings #abg #g4 ,remodelling of ,outlets #aca #h4 ,miscellaneous ,items #acg ,,chapter ,,iv ,,the ,,punjab ,,triple ,,canal ,,project #a4 ,general ,description #add #b4 ,areas and ,discharges #adg #c4 ,remarks #aef ,,chapter ,v ,,proposed ,,improvements ,,in ,,irrigation ,,canals #a4 ,preliminary ,remarks #aeh #b4 ,reduction of ,losses in the ,channels #aei #c4 ,modules #afb ,,appendices ,a4 ,divide ,wall on ,lower ,chenab ,canal #afi ,b4 ,specification for ,maintenance of ,channels #aga ,c4 ,specification for ,maintenance of ,masonry ,works #agd ,d4 ,watching and ,protecting ,banks and ,embankments #age ,e4 ,specification for ,bushing #agh ,f4 ,escapes #ahj ,g4 ,gauges #ahc ,h4 ,gibb's ,module #ahf ,k4 ,kennedy's ,gauge ,outlet #aic ,,index #aif ,,preface ,when ,river and ,canal ,engineering was written it was decided to omit ,irrigation works and to deal with them separately because the subject interests chiefly specialists4 ,the present book deals with the principles which govern the design and management of ,irrigation works1 and it discusses the ,canals of ,northern ,india--the largest and best in the world--in detail4 ,some years ago a number of rules for designing distributaries were framed1 at the request of the ,punjab ,government1 by the late ,colonel ,s4 ,l4 ,jacob1 ,c4,i4,e41 ,r4,e41 and comments on these rules were obtained from many experienced engineers and recorded4 ,the author has had the advantage of reading all these opinions4 ,generally the weight of opinion on any point agrees with what most experienced engineers would suggest1 and direct conflicts of opinion scarcely occur4 ,important papers have been printed by the ,punjab ,irrigation ,branch on ,losses of ,water and the ,design of ,distributaries1 on the great ,triple ,canal ,project1 on ,gibb's ,module1 on ,kennedy's ,gauge ,outlet1 and on the ,lining of ,watercourses4 ,these papers are not always accessible to engineers1 and the chief points of interest in them are not1 in most cases1 discernible at a glance4 ,such points have been extracted and are given in this book4 ,e4 ,s4 ,b4 ,,cheltenham1 ,may #bjth1 #aiac4 ,,irrigation ,,works4 ,,chapter ,i4 ,,introduction #a4 ,preliminary ,remarks4--,the largest irrigation canals are fed from perennial rivers4 ,when the canal flows throughout the year it is called a 8,perennial ,canal40 ,chief among these are the canals of ,india and particularly those of ,northern ,india1 some of which have bed widths ranging up to #cjj feet1 depths of water up to #aa feet and discharges up to #aj1jjj c4 ft4 per second4 ,other large canals as for instance many of those in ,scinde1 ,egypt and the ,punjab1 though fed from perennial rivers1 flow only when the rivers are high4 ,these are called 8,inundation ,canals40 ,many canals1 generally of moderate or small size1 in other countries and notably in the ,western ,states of ,america1 in ,italy1 ,spain1 ,france and ,south ,africa1 are fed from rivers and great numbers of small canals from reservoirs in which streams or rain-water have been impounded4 ,sometimes water for irrigation is pumped from wells and conveyed in small canals4 ,in ,australia a good deal of irrigation is effected from artesian wells4 ,irrigation works on a considerable scale are being undertaken in ,mexico and the ,argentine4 ,in this book1 irrigation works of various countries are referred to and to some extent described1 but the perennial canal of ,northern ,india1 with its distributaries1 is the type taken as a basis for the description of the principles and methods which should be adopted in the design1 working and improvement of irrigation channels and it is to be understood that such a canal is being referred to where the context does not indicate the contrary4 ,any reader who is concerned with irrigation in some other part of the world will be able to judge for himself how far these principles and methods require modification4 ,the branches and distributaries--all of which are dealt with--of a large perennial canal cover all possible sizes4 ,,chapter ,,ii4 of this book deals with the design of canals and ,,chapter ,,iii4 with the working of canals but as the two subjects are to some extent interdependent1 they will both be dealt with in a preliminary manner in the remaining articles of the present ,chapter4 ,,chapter ,,iv4 describes the ,punjab ,triple ,canal ,project4#a ,,chapter ,v4 deals with certain proposed improvements in the working of canals4 #a ,the latest example of canal design4 #b4 ,general ,principles of ,canal ,design4--,the head of a canal has to be so high up the river that1 when the canal is suitably graded1 the water level will come out high enough to irrigate the tract of land concerned4 ,if a river has a general slope of a foot per mile and if the adjoining country has the same slope and is a foot higher than the water level of the river1 and if a canal is made at a very acute angle with the river1 with a slope of half a foot per mile1 the water level about two miles from the canal head will be level with the ground4 ,the headworks of the canal consist of a weir--which may be provided with sluices--across the river1 and a head 8regulator10 provided with gates1 for the canal4 ,there are however many canals1 those for instance of the inundation canal class1 which have no works in the river and these may go dry when the river is low4 ,they usually have a regulator to prevent too much water from going down the canal during floods4 ,if a canal is fed from a reservoir the headworks consist simply of a sluice or sluices4 ,a canal must be so designed as to bring the water to within reasonable distance of every part of the area to be irrigated4 ,unless the area is small or narrow the canal must have 8branches0 and 8distributaries40 ,a general sketch of a large canal is given in ,fig4 #a4 ,on a large canal1 irrigation is not usually done directly from the canal and branches4 ,it is all done from the distributaries4 ,illustration3 ,,fig4 #a4 ,from each distributary 8watercourses0 take off at intervals and convey the water to the fields4 ,a small canal1 say one whose length is not more than #ae miles or whose discharge is not more than #ajj c4 feet per second1 may be regarded as a distributary and the word distributary will be used with this extended meaning4 ,it is not always the case that the whole tract covered by a system of canal channels is irrigated4 ,in the case of a canal fed from a river1 the land near the river is often high or broken and the main canal runs for some distance before it reaches the tract to be irrigated4 ,again1 within this tract there are usually portions of land too high to be irrigated4 ,those portions of the tract which can be irrigated are called the 8commanded area40 ,the channels of a large irrigation system should run on high ground4 ,in the case of a distributary1 this is necessary in order that the water-courses may run downhill1 and since the water in the canal and branches has to flow into the distributaries1 the canal and branches must also be in high ground4 ,another reason for adopting high ground is that all the channels should1 as far as possible1 keep away from the natural drainage lines of the country and not obstruct them4 ,also a channel in high ground is cheapest and safest4 ,when a channel is in low ground it must have high banks which are expensive to make and liable to breach4 ,every tract of country possesses more or less defined ridges and valleys4 ,when the ridges are well defined1 the irrigation channels1 especially the distributaries1 follow them approximately1 deviating slightly on one side or the other from the very top of the ridge in order to secure a more direct course4 ,if any part of a ridge is so high as to necessitate deep digging the channel does not necessarily go through it4 ,it may skirt it and return to the crest of the ridge further on1 especially if this arrangement shortens the channel or at least does not lengthen it much4 ,a channel also goes off the ridge sometimes when adherence to it would give a crooked line4 ,of course all the channels--canals1 branches and distributaries--have to flow more or less in the direction of the general slope of the tract being dealt with4 ,illustration3 ,,fig4 #b4 ,the alignments of the channels do not1 however1 depend exclusively on the physical features of the country4 ,centrality in the alignment is desirable4 ,it will be shown 7,,chap4 ,,ii4 ,art4 #aj7 that a distributary works most economically when it runs down the centre of the tract which it has to irrigate4 ,it is better to have short watercourses running off from both sides of a distributary than long watercourses from only one side4 ,the same is true of a branch2 it should run down the centre of its tract of country4 ,again the angles at which the channels branch off have to be considered4 ,if branches were taken off very high up the canal and ran parallel to and not far from it1 there would be an excessive length of channel4 ,but neither should the branches be so arranged as to form a series of right angles4 ,in the case shown in ,fig4 #b the size of the main or central canal would of course be reduced at the point ,a4 ,by altering the branches to the positions shown in dotted lines their length is not appreciably increased while the length ,a ,b is made of the reduced instead of the full size4 ,moreover the course ,b ,c is more direct than ,,bac and this may be of the greatest importance as regards gaining the necessary command4 ,when a channel bifurcates1 the total wet border always increases and there is then a greater loss from absorption4 ,the water is always kept in bulk as long as possible4 ,if the alignment of a branch is somewhat crooked it does not follow that straightening it--supposing the features of the country admit of this--will be desirable4 ,it may increase the length of distributaries taken off near the bends4 ,it will be shown 7,,chap4 ,,ii4 ,art4 #aj7 that a distributary ought1 when matters can be so arranged1 to irrigate the country for two miles on either side of it1 and watercourses should be two or three miles long4 ,a distributary need not therefore extend right up to the boundary of the commanded area but stop two or three miles from it4 ,generally it is not desirable to prolong a distributary and make it 8tail0 into another channel 7,,chap4 ,,ii4 ,art4 #c74 ,a distributary1 like a canal1 may give off branches4 ,none of the rules mentioned in the preceding paragraph are intended to be other than general guides1 to be followed as far as the physical features of the country permit1 or to assist in deciding between alternative schemes4 ,it may for instance be a question whether to construct one distributary or two1 between two nearly parallel branches4 ,the two-mile rule may enable the matter to be decided or it may influence the decision arrived at as to the exact alignments of the branches4 ,the flatter the country and the less marked the ridges the more the alignment can be based on the above rules4 ,sometimes1 as in the low land adjoining a river1 the ridges are ill defined or non-existent and the alignment is based entirely on the above rules4 ,the rule as to following high ground need not be adhered to at the tail of any distributary if all the land to be irrigated at the tail is low and if there is a deep drainage line or other feature of the country such as to preclude the possibility of an extension of the distributary4 ,possible extensions should always be considered4 ,in hilly districts an irrigation canal may have to run in sidelong ground along the side of a valley4 ,in flat valleys1 owing to the land nearest the river having received successive deposits of silt in floods1 the ground generally slopes away from the river and a canal can irrigate the low land even if taken off at right angles to the river4 ,but to irrigate the high land near the river and the land where it rises again towards the hills or watershed1 a canal taking off higher up the river is necessary4 ,of course much depends on whether the canal is to irrigate when the river is low or only when it is high1 and whether or not there is to be a weir in the river4 ,in ,upper ,egypt1 it is common for a high level canal taking off far upstream1 to divide into two branches1 one for the land near the river and one for the land towards the watershed1 and for both branches to be crossed--by means of syphons--by a low-level canal which irrigates the low ground4 ,similar arrangements sometimes occur on ,indian inundation canals4 ,regulators are usually provided at all off-takes of branches4 ,in the case of a channel taking off from another channel many times its own size there is generally only the head regulator of the smaller channel but in other cases there is a regulator in each channel below the bifurcation4 ,thus1 when the number of bifurcating channels is two it is called a double regulator4 ,regulators1 with the 8falls0--introduced to flatten the gradients when the slope of the country is too steep--and drainage crossings and the bridges1 provided at the principal roads1 constitute the chief masonry works on a canal4 ,at a fall1 mills are often constructed or the fall may be used for electric power4 ,regarding curves and bends in channels1 it is explained in ,river and ,canal ,engineering that1 as regards increased resistance to flow and consequent tendency to silt deposit1 curves of fair radius have very little effect1 that a curve of a given angle may perhaps have the same effect whether the radius is great or small but that if the radius is large a succession of curves cannot be got into a short length1 that a succession of sharp curves in a short length may have great effect1 amounting to an increase of ,n in ,kutter's co-efficient1 that a single sharp curve has not much effect1 that the chief objection to such a curve is the tendency to erosion of the bank1 that at a place where the channel has1 in any case1 to be protected1 as for instance just below a weir or fall1 there is no objection to the introduction of a sharp bend and that such bends1 in fact right-angled elbows1 exist without any evil effects at many regulators when the whole supply is being turned into a branch4 ,it is remarkable that on perennial canals no advantage is ever taken of the last mentioned fact4 ,cases undoubtedly occur1 though somewhat infrequently1 in which the most suitable and cheapest arrangement would be to give a canal an abrupt bend at a fall4 ,in order to reduce eddying1 the bend need not be an absolute elbow but can be made within the length of the pitching which would be curved instead of straight4 ,this is frequently done on inundation canals1 without the slightest drawback1 even when there is no fall1 the pitching at bridges being utilised4 ,a pitched bend can be made anywhere4 ,when a river floods the country along its banks as in parts of ,egypt and of the ,punjab1 it is generally necessary to construct marginal embankments before irrigation can be introduced4 ,the canal may take off at a point where flooding does not occur or it may pass through the embankment4#b ,if it passes through at a point where flooding occurs1 a masonry regulator is constructed to prevent the floods from enlarging the gap and breaking into the country4 #b ,for detailed accounts of such embankments and canals see ,punjab ,rivers and ,works 7,spon7 #aiab4 ,a large canal is provided1 so far as is practicable1 with 8escapes0 by means of which surplus water may be let out4 ,surplus water occurs chiefly after rain4 ,at such times the demand for water may suddenly be reduced and if there were no escapes there would probably be serious breaches of the banks before there was time for the reduction of water1 effected at the head of the canal1 to take effect lower down4 ,there is usually an escape at some point in the main line1 preferably at a point where it divides into branches1 and this escape runs back to the river4 ,there may also be escapes near the tails of the longest branches4 ,these escapes may discharge into drainages or into reservoirs formed by running a low embankment round a large area of waste land4 ,the drainage of the whole tract irrigated by a canal must be carefully seen to4 ,the subsoil water level of a tract of country is nearly always raised by an irrigation canal4 ,the rise near to a canal or distributary is due to percolation from the channel and is inevitable4#c ,the rise at places further away1 if it occurs1 is due to over-watering or to neglect of drainage4 ,immense damage has been done by 8water-logging0 of the soil when irrigation water has been supplied to a tract of flat country and the clearance and improvement of the natural drainages has not been attended to4 ,any drainages crossed by the banks of the irrigation channels should be provided with syphons or aqueducts or else the drainage diverted into another channel4 ,very frequently the main line of a canal--whether great or small--in the upper reaches near the hills1 has to cross heavy drainage channels or torrents and large and expensive works are required for this4 #c ,but see ,chap4 ,v4 as to reduction of percolation4 ,near the head of a canal and of every branch and distributary1 there is an ordinary gauge which shows the depth of water and is read daily4 ,the gauge near the head of a main canal is generally self-registering4 ,the principles sketched out in this article are those generally followed in the designs of modern canals4 ,they have by no means been followed in all cases4 ,in some of the older ,indian canals both the canal and the distributaries ran in low ground4 ,water-courses took off direct from the canals1 and the irrigation did not generally extend far from the canal4 ,in fact long distributaries were impracticable because they would have run into high ground4 ,the banks of the channels obstructed drainages and caused pestilential swamps4 ,most canals of this type have been abolished since the advent of ,british rule and replaced by others properly designed4 ,some badly designed canals however1 mostly of the inundation class1 still exist but in very dry tracts where drainages are of little consequence4 #c4 ,information ,concerning ,canals4--,nearly all canal irrigation is done by 8flow10 the water running from the water-courses onto the fields1 but a small proportion is done by 8lift40 ,this is done in the case of high pieces of land1 the lifting being usually done by pumps or1 in the east1 by bullocks or by manual labour4 ,irrigation generally consists in giving the land a succession of waterings1 one previous to ploughing and others after the crop is sown1 each watering being of quite moderate depth4 ,on inundation canals in ,india the waterings for the summer crop are thus effected but for the winter crop the land is deeply soaked during the flood season and is afterwards ploughed and sown4 ,in ,upper ,egypt this system is emphasised1 the water flowing into vast basins1 formed by dykes1 where it stands for some time and1 after depositing its silt1 is drained off4 ,until recent times the whole of the irrigation of ,egypt was basin irrigation4 ,in ,lower ,egypt the construction of the ,nile barrage led to the introduction of canals which take off at a proper level and their working is not restricted to the period when the river is in flood4 ,in ,upper ,egypt most of the irrigation is still basin irrigation but the canals taking off above the ,assiut barrage form a notable exception4 ,by means of the ,assouan dam which crosses the ,nile1 the water during the latter part of the flood season and after the floods are over1 i4e4 from ,november to ,march1 is ponded up and a vast reservoir formed and the impounded water is let down the river in ,may and ,june4 ,in some of the older irrigation canals of ,india the velocity was too high and the channels have since had to be remodelled and the crests of weirs raised or new weirs built4 ,the more recent canals are free from grave defects of this kind but every canal undergoes changes of some kind and finality has never yet been quite attained4 ,on some ,indian irrigation canals made about #cj years ago1 great sums of money were wasted in making the canals navigable4 ,there is nothing like enough navigation to pay for the extra cost4 ,the idea has now been quite given up except as regards timber rafting from upstream4 ,this requires no curtailment of the velocity in the channels4 ,the requirements of the irrigation and navigation were always in conflict4 ,the mere fact that branches have to be worked in turns is enough to prevent navigation succeeding4 ,in ,india the water used for irrigation is paid for1 not according to the volume used but according to the area irrigated4 ,the volume used in any particular watercourse is not known4 ,the areas sown are measured4 ,certain kinds of crops use up more water than others and the charges are fixed accordingly4 ,in the canals which have their headworks among the mountains of ,western ,america there are frequent tunnels and syphons and the canals often run in steep sidelong ground4 ,there are great lengths of tunnel and syphon in the ,marseilles and ,verdun ,canals and there are long tunnels in the ,periyar ,canal in ,madras and in the ,upper ,swat ,canal in the ,north ,west ,frontier ,province of ,india4 ,the ,tieton ,canal1 ,washington1 ,u4,s4,a41 traverses steep sidelong ground which would be liable to slip if a large cutting were made4 ,the cross-section of the channel is a circle1 #h-;ft4 #c-;ins4 in diameter1 with the upper part removed1 so that the depth is #f feet4 ,it is made of reinforced concrete #d inches thick and the sides are tied together by iron bars which run across the channel above the water4 ,in the ,santa ,ana ,canal the channel consists for #b miles of a flume made of wooden 8staves40 ,a canal constructed in ,wyoming1 ,u4,s4,a41 after taking off from a river1 passes through a tunnel into another valley and is turned into another stream which thus becomes the canal4 ,this is said to save loss of water by percolation4 ,the stream is winding while a canal could have been made straighter4 ,there may1 owing to the ground near the stream being saturated1 have been less loss of water at first than there would have been in the artificial channel but1 owing to the smaller wetted area1 there would probably have been an eventual saving in adopting the latter4 ,the real advantage of adopting the natural stream was probably a saving in the cost of construction4 7,min4 ,proc4 ,inst4 ,c4,e4 ,vol4 ,,clxii47 ,irrigation from canals which are supplied from reservoirs differs in no respect from that from other canals4 ,the principles on which reservoir capacities should be calculated and earthen and masonry dams constructed are given in ,river and ,canal ,engineering4 ,sometimes1 as for instance when a reservoir becomes seriously reduced in size owing to silt deposit1 the water is run off after the bed of the reservoir has been soaked1 and crops are grown on the soaked soil4 ,the distribution of the water of a canal as between the main channel and the branches1 is effected by means of the regulators at the bifurcations4 ,when the supply is ample and the demand great1 the channels may all be running nearly full4 ,when the demand exceeds the supply1 the water may be reduced proportionately in each branch but this may result in the water of a branch being too low to give proper supplies to the distributaries or some of them1 and in the water of a distributary not commanding the higher ground4 ,moreover it violates the principle of keeping the water in bulk as far as possible4 ,it is more usual to give each branch full supply1 or a certain large fraction of the full supply1 in turn1 and similarly with the distributaries4 ,the method of distribution from a distributary to the watercourses varies4 ,in many modern canals there is1 at each watercourse head1 a sluice which is adjusted at frequent intervals according to the supply and the demand4 ,one method1 which is excellent because it fulfils in the highest degree the principle of keeping the water in bulk1 is to have very large watercourses and1 by means of regulators which are built at frequent intervals1 to turn the whole of the water of the distributary into a few watercourses at a time1 beginning with those nearest the head of the distributary and working downstream4 ,but a system which seems eminently suitable may be impracticable because of local circumstances4 ,in ,india1 any such arrangement would need an army of officials and would lead to unbounded corruption4 ,in ,india the water from a distributary enters the watercourses through 8outlets0 which are small masonry tubes passing through the banks of the distributary4 ,there is no easy way of closing these outlets or at least of keeping them closed if the cultivators choose to open them1 but it is easy to close a whole distributary and so regulate the supply4 ,this is the chief reason why watercourses in ,india do not usually take off direct from the canals4 ,the presence of silt in the water of a river from which a canal is drawn is often spoken of as being a great evil4 ,if it is an evil at all it is a very mixed evil4 ,the deposits of silt in the channels have been enormously reduced by the application of scientific principles of design4 ,the clayey silt which remains in the water and reaches the fields1 brings to them greatly increased fertility4 ,in ,india the fertility of the soil is often reduced or destroyed by the formation on the surface of the ground of an efflorescence called 8reh40 ,it consists of various salts or compounds of sodium and occurs chiefly where there is an impervious layer of subsoil4 ,the salts exist as an ingredient of the upper soil4 ,this becomes saturated with rain or canal water and as the water evaporates the salts are left on the surface4 ,remedies are drainage1 or flooding the soil and running the water off1 or deep tilling1 or chemical treatment with lime or gypsum4 7,indian ,engineering1 #hth ,jan41 #aiaj74 ,the inundation canals of the ,punjab have been described in ,punjab ,rivers and ,works4 ,all descriptions and remarks in the present book regarding ,indian canals must be assumed to refer to perennial canals unless the contrary is stated or implied4 #d4 ,losses of ,water4--,when water flows or stands in an earthen channel or tank1 or is spread over a field1 losses occur from evaporation1 percolation and absorption4 ,of these1 absorption is by far the most important and1 unless the contrary is stated or implied1 it will be taken to include the others4 ,the losses by evaporation are very small4 ,the loss by evaporation from the surface of the water1 even in the hot season in ,india when a hot wind often blows1 does not exceed half an inch in #bd hours and on the average in ,india is only about a tenth of an inch in #bd hours4 ,illustration3 ,,fig4 #c4 ,percolation and absorption are described as follows by ,beresford in ,punjab ,irrigation ,paper1 ,no4 #aj1 8,the ,irrigation ,duty of ,water40 ,percolation consists in flow through the interstices of boulders1 shingle1 gravel or coarse sand4 ,the flow is similar to that in pipes4 ,the water percolating into the soil from a channel1 extends downwards and spreads outwards as it descends4 ,none of it goes upwards4 ,in fine sand and ordinary soil the interstices act like capillary tubes4 ,the water is absorbed as by a sponge and it remains in the soil by virtue of capillarity4 ,owing to the combined action of capillarity and gravity the water spreads in the manner shown by the dotted lines in ,fig4 #c4 ,the amount of absorption from a channel will be greater the greater the area of the wetted surface4 ,in a high embankment with narrow banks1 the absorption ceases when the water reaches the outer slopes1 except in so far as it is evaporated from the slopes4 ,moreover high embankments are generally in clayey soil4 ,if banks of sand are constructed on a layer of clay 7,fig4 #d47 and well rammed1 the absorption ceases as soon as the banks are saturated and the channel then holds water as well as any other except for evaporation from the outer slopes1 but if the bed and subsoil are also of sand the absorption of the water will be far greater4 ,absorption ceases when the water extends nearly down to the level of the subsoil water1 i4e41 to a point where the effect of absorption from above plus gravitation is equal to the effect of absorption from below minus gravitation4 ,if a bottle is filled with water and a small sponge jammed into the neck and the bottle turned upside down1 the sponge becomes saturated but no water will be given out4 ,but if a dry sponge is placed in contact with the wet one it will absorb moisture until saturated4 ,illustration3 ,,fig4 #d4 ,it is known that the loss of water is greatly influenced by the nature of the soil4 ,when water is turned into a dry channel or onto a field1 the loss is at first great4 ,it decreases hourly and daily and eventually becomes nearly constant1 tending to reach a fixed amount when the water extends down to nearly the level of the subsoil water4 ,observations made by ,kennedy on loamy fields near the ,bari ,doab ,canal in ,india showed that on a field previously dry the rate of absorption is given by the equation y #jhiax#hf4 ,where y is the depth of water absorbed in feet and x is the time in hours4 ,the observations extended over eight days4 ,denoting by c the depth of water in feet absorbed in one hour1 it was found that on a field on which no rain had fallen for two months1 c was #jd to #je but on the second watering of the crop about a month later c was #jb to #jc and about the same on a third watering4 ,it was found that at the first commencement the rate of absorption was much affected by the state of the surface of the ground but that the effect was only temporary4 ,the losses were found to be as follows3 ----------------------------------- ,,day4 ,,loss ,,per ,,day4 ,,loss ,,per ,,hour4 7c7 ----------------------------------- ,feet4 ,feet4 #ast #acf #jeg #bnd #aac #jdg #crd #ajg #jdf #dth #ajb #jdc #eth #if #jda #fth #ij #jcg #gth #hj #jcc #hth #gg #jcb ,total #hja ----------------------------------- ,in the eight days the total loss was almost exactly eight feet4 ,the losses by absorption in the various channels of certain canals has been estimated to be as follows3-- ---------------------------------------- ------------------------- ,channel4 ,nature,mean depth ,value ,loss per ,remarks4 of of water of ,million soil4 in 7c7 square feet ,channel4 of wetted surface4 ---------------------------------------- ------------------------- ,feet4 c4 ft4 per sec4 ,main ,line ,upper,shingle #f #jce #ig ,bari ,doab ,canaland ,sandy ,soil ,fairly reliable ,main ,line ,sandy #g #ij estimates based ,sirhind ,canal ,soil on discharge observations4 ,branches ,upper ,loam #jjgi #bb ,bari ,doab ,canal ,branches ,sandy #eb ,sirhind ,canal ,soil ,distributaries ,loam #jabdbc to #dd ,upper ,bari 7average ,doab ,canal #cc7 ,distributaries ,sandy #e to #ab ,sirhind ,canal ,soil 7average #hj7 ,somewhat rough estimates4 ,watercourses ,loam #jaed #cc to #bj ,upper ,bari to 7average ,doab ,canal #jdee #id7 ,watercourses ,sandy #g to #fj ,sirhind ,canal ,soil 7average #bb7 ---------------------------------------- ------------------------- #d ,when the channel was in continuous flow4 #e ,maximum value when flow was intermittent4 ,some information as to losses of water is also given in ,,chapter ,,iv4 ,art4 #b4 ,the relative losses of water in the channels of the ,upper ,bari ,doab ,canal were as follows3-- ,relative ,loss4 ,in main line and branches #bj ,in distributaries #f ,in watercourses #ba ,used in the fields #ec --- ,total #ajj ,the reasons for the great variation in the value of c are not properly known4 ,the depth of water is not likely to have much influence on it4 ,it is well known that the fine silt carried by the water tends to render the channels watertight when it deposits4 ,the canals and branches receive either no deposits or deposits consisting chiefly of sand4 ,the distributaries1 especially in their lower reaches1 receive deposits of fine silt which is only occasionally cleared away4 ,the watercourses receive similar deposits but they are very frequently cleared out by the cultivators4 ,this is perhaps the reason why the rate of loss of water in the watercourses is nearly three times as great as the rate of loss in the distributaries of the same canal4 ,on the ,sirhind canal the distributaries have more branches than on the ,bari ,doab canal and the watercourses are smaller4 ,this accounts for the different relative losses in the two cases4 ,the sandy nature of the soil on the ,sirhind canal accounts for the general higher value of c on that canal4 ,the following formula has been deduced as giving the loss by absorption on a ,punjab ,canal4 ,,wl ,p #ce d --------- #a1jjj1jjj ,where ,p is the loss by absorption in c4 ft4 per second in a reach whose length is ,l1 width 7at water level7 ,w and depth d4 ,according to the formula the loss per million square feet is #aje c4 ft4 per second when d is #d ft4 and #g c4 ft4 per second when d is #b feet1 ,these figures do not agree with those in the preceding table and it is clear that there are not yet sufficient data from which to construct a formula4 ,the first steps taken on the ,bari ,doab ,canal1 and subsequently on other canals1 to reduce the losses of water1 consisted in the reduction in the number of watercourses4 ,this will be referred to again 7,,chapter ,,ii4 ,art4 #i74 ,further steps will be considered in ,,chapter ,v4 #e4 ,duty of ,water4--,the number of acres irrigated annually by a constant discharge of #a c4 ft4 of water per second is called the 8duty0 of water4 ,in ,india on perennial canals the duty may be as much as #bej or even #cjj acres4 ,on inundation canals which flow for only five months in the year and are situated in tracts of scanty rainfall and light or sandy soil1 the duty may be only #gj acres4 ,the duties of most existing canals whether in ,india or elsewhere1 are known only approximately4 ,the duty is calculated on the average discharge entering the canal at its head less the water which is passed out at escapes4 ,it thus includes all losses of water4 ,the duty varies not only as between one canal and another but on the same canal from year to year4 ,it depends on the character of the soil1 a sandy soil requiring more water than a clayey soil4 ,it also depends on the rainfall4 ,a moderate amount of rain causes the canal water to go further1 but heavy rain may enable some crops to do without canal water or may permit of the concealment of canal irrigation4 ,the duty also depends on the kind of crops grown1 on the losses in the channels by absorption and on the quantity of water available4 ,a liberal supply of water leads to carelessness in the use1 but a very restricted supply is largely wasted owing to the shortness of the 8turns0 or rotational periods of flow in the different channels4 ,there is an obvious connection between the duty of water and the total depth of the water1 known in ,india as 8delta10 given to the fields4 ,calculations are much simplified1 while still being accurate enough for all practical purposes1 by assuming that the number of seconds1 7#hf1djj7 in a day is twice the number of square feet1 7#dc1efj7 in an acre4 ,assuming this to be the case a discharge of #a c4 ft4 per second for a day gives #b acre-feet1 i4e41 it will cover an acre of ground to a depth of #b feet in a day2 and in six months it will cover #ajj acres to depth of #cfe feet4 ,in ,northern ,india the year is divided into two halves in each of which a crop is grown and the duty is calculated for each crop4 ,in this case1 if the flow of a canal has been continuous1 a duty of #ajj acres per cubic foot of its mean discharge per second1 corresponds to a total depth of #cfe feet over the area irrigated4 ,generally the flow in the half-year has not been continuous4 ,in other countries1 and in ,india on canals other than the perennial canals1 the periods of flow vary a great deal4 ,the duty cannot be calculated from delta or vice versa until the period of flow is stated4 ,the daily gauge-readings and daily discharges corresponding to them1 having been booked1 the discharges are added up4 ,the total1 divided by the number of days on which the canal has been running1 gives the average daily discharge4 ,suppose that during the 8kharif0 or summer crop which is considered to last from #ast ,april to #cjth ,september or #ahc days1 the canal was closed for #ac days and that the total of the daily discharges on the remaining #agj days comes to #hej1jjj c4 ft4 per second4 ,the average daily discharge is #e1jjj c4 ft4 per second4 ,suppose the kharif area irrigated to be #ejj1jjj acres1 the kharif duty is #ajj acres4 ,to find delta the total of the daily discharges has to be multiplied by the number of seconds in a day and divided by the number of square feet in an acre 7these figures are1 as already stated1 very nearly in the ratio of two to one7 and divided again by the number of acres irrigated4 ,thus1 in the above case1 delta is very nearly #hej1jjj #b_/ejj1jjj or #cd feet4 ,for comparing the results of one canal or one year with another1 delta is the more convenient figure to take4 ,as soon as the areas irrigated by the canals are known for any crop1 the ,chief ,engineer of the province issues a statement of the value of delta for each perennial canal and compares them with those for previous years4 ,the value of delta for the ,punjab canals ranges from #c to #d feet for the kharif and from #ah to #ba feet for the 8rabi0 or winter crop4 ,individual canals vary greatly1 the worst having nearly twice as high a figure as the best4 ,the differences are due to the causes already mentioned4 ,although the figures of duty take no account of the number of days a canal was closed1 they are the most convenient standard for judging generally of the work likely to be done by a projected canal4 ,it will readily be seen that figures of duty are not exact and are only an approximate guide4 ,the delta figures are1 on the perennial canals of the ,punjab1 also worked out for each month of the crop1 the volume of water used from the beginning of the crop up to the end of the month being divided by the area irrigated up to the end of the month4 ,but when irrigation is in full swing1 some little delay occurs in booking the fields4 ,moreover the same field is watered a number of times during the crop and much depends on whether waterings have just been given or are just about to be given4 ,the figures are useful to some extent for comparison4 ,the figures for the rabi crop of #aijh-ji were as follows1 the figure for ,march being the final figure for the crop4 ,up to end of ,oct41 ,nov41 ,dec41 ,jan41 ,feb41 ,march4 ,progressive value of delta4 #afi #acd #abi #adg #aga #bje4 ,one great principle to be followed in order to obtain a high duty is to restrict the supply of water4 ,a cultivator whose watercourse is always running full may waste great quantities of water1 but if he knows that it is only to run for a few days out of a fortnight he will use the water carefully4 ,it is not1 of course1 meant that the water kept back is run into escapes and wasted4 ,it goes to irrigate other lands4 ,the available supply of water should be spread over as large an area of land as just1 and only just1 to suffice4#f ,other methods of improving the duty are the reduction in the number of watercourses1 the apportionment of the sizes of outlets1 watercourses and distributaries to the work that they have to do1 careful attention to the distribution of the water and the prevention of wastage due to carelessness4 #f ,a system of lavish supply is in most cases likely to lead to harm by water-logging of the soil or its exhaustion by over-cropping or to raising of the spring level and injury to the public health4 ,the following information concerning duties is taken from ,buckley's ,irrigation ,pocket ,book3-- ---------------------------------------- ----- ,,place4 ,,rabi ,,duty4 ,,kharif ,,duty ---------------------------------------- ----- ,acres ,acres ,upper ,india #ace to #bcgg #di to #abj 7,punjab and ,united ,provinces7 ,lower ,chenab ,canal#hacc to #acd #dg to #hh 7,punjab7 ,bengal #ef to #acj #eg to #aac ,bombay #he to #aah #eh to #aei ---------------------------------------- ----- #g ,occasionally as low as #ih or even #fb4 #h ,the most recent canal4 ,the period of flow in each case would be six months or less4 ,the average rabi duties on the ,lower ,chenab and ,upper ,bari ,doab ,canals1 in the ,punjab1 calculated on the discharges at the distributary heads1 for periods of #c and #e years respectively1 ending ,march1 #aijd1 were #bjh and #bfc acres respectively1 but in the latter case #aa per cent4 of the area received only 8first waterings40 ,for the kharif the figures are #ajj and #ih respectively4 ,in ,italy the duty is #ee to #gj acres1 in ,spain from #de to #bje acres1 in the ,western ,states of ,america generally #fj to #aej acres4 ,in ,south ,california the duty is #aej to #cjj acres1 when1 as is usual1 surface irrigation is employed1 but #cjj to #ejj acres with subsoil irrigation1 the water being delivered in a pipe below ground level 7,,chapter ,v47 ,in basin irrigation in ,egypt the duty is #bj to #be acres1 but the period of flow is only #dj days4 ,the basins are flooded to about #c feet in depth4 #f4 ,sketch of a ,project4--,the tract of country to be dealt with in an irrigation project may be limited either by the natural features of the country1 by its levels1 by the quantity of water available or by financial considerations4 ,if the tract is small or narrow1 and particularly if it is not very flat1 it may be obvious that there is only one line on which the irrigation channel can conveniently be constructed but in any considerable scheme a contour plan of the whole tract is absolutely necessary4 ,the surveys for such a plan are expensive and take time and it is desirable1 as far as possible1 to settle beforehand the area over which they are to extend4 ,this may be done to some extent by the examination of any existing levels and of the tract itself4 ,very high1 sandy or swampy ground1 whether occurring at the edge of the tract or in the middle of it1 may have to be left out4 ,the remainder1 as already mentioned1 is called the commanded area4 ,when land occupied by houses or roads or which is very much broken1 or which for any reason cannot be irrigated1 has also been deducted1 the balance is the 8culturable commanded area40 ,either before or after the culturable commanded area has been approximately ascertained1 the proportion of it which is to be irrigated must be settled4 ,this depends on local circumstances4 ,in ,india the supply of water is calculated on the supposition that a fraction1 generally from to 1 of the culturable commanded area will be irrigated each year4 ,the rest will be lying fallow or be temporarily out of use or be used for crops which do not require canal irrigation4 ,the restriction of the area is necessary either because the supply of water is limited or in the interests of the people4 ,too liberal a supply of water tends1 as already stated1 to over cultivation1 and exhaustion and water-logging of the soil4 ,the next step is to estimate the duty and the discharge of the canal and then to fix its main dimensions4 ,in ,northern ,india the duty in the rabi is higher than in the kharif4 ,it may be #bjj acres in the rabi and #ajj acres in the kharif4 ,local circumstances determine which crop has the greater area4 ,suppose that it is estimated that both will be equal4 ,then the total annual area for which water is to be provided must be divided by two and this gives the kharif area4 ,during the kharif there is usually an ample supply of water and the kharif mean supply of the canal is based on the kharif area and the kharif duty4 ,the full supply is not run all through the crop because the demand fluctuates1 the demand being greatest when all the crops have been sown and when there is no rain1 but from experience of other canals the ratio of the kharif full supply to the kharif mean supply can be estimated4 ,the ratio is generally about #abe4 ,on the kharif full supply depends the size of the channel1 every channel being constructed so as to carry a certain 8full supply0 or maximum discharge and the top of the bank being made at such a height that there shall be a sufficient margin or 8free-board0 above the 8full supply level40 ,the canal runs full provided that there is a sufficient supply in the river or that the water level of the river is high enough--this last condition referring to canals which have no weir in the river--and provided also that there is a sufficient 8demand0 for the water4 ,at other times a canal runs with less than full supply4 ,this generally occurs throughout most of the rabi1 the supply of water in the river being then restricted4 ,the distributaries are generally run full or ths full1 some being closed1 in turn1 to give water to the others4 ,in the case of a country where there is only one crop in the year1 the average discharge of the canal can be found by dividing the area by the estimated duty4 ,the ,f4,s4 discharge can be assumed to bear such a relation to the average discharge as may be found by experience to be suitable4 ,on some ,indian inundation canals the ,f4,s4 discharge is taken as twice the average discharge4 ,the ,f4,s4 discharge of the canal having been arrived at1 the alignments of the canal and branches are next sketched out on the contour plan and certain tracts and discharges are assigned to each branch4 ,the gradients can be ascertained from the levels of the country and the cross-section of the channel can then be sketched out4 ,if the velocity is too great for the soil 8falls0 can be introduced4 ,the above procedure will enable a rough idea to be formed of the cost of the earthwork of the scheme4 ,the cost of the headworks and masonry works and distributaries can be best estimated by obtaining actual figures for existing works of similar character1 the distributaries being reckoned at so much per mile4 ,the probable revenue which the canal will bring in will depend upon the rate charged for the water and the cost and maintenance1 matters which can only be determined by local considerations based on the figures for existing canals4 ,the masonry works on a canal consist of the headworks and of bridges1 regulators and drainage crossings4 ,the principles of design for such works have been dealt with in ,river and ,canal ,engineering4 ,it is of course economical to make a bridge and fall in one4 ,if the off-take of a distributary is anywhere in the neighbourhood the fall should of course be downstream of it4 ,the positions of the falls should be fixed in accordance with these considerations4 ,if the longitudinal section is such that the position of the fall cannot be much altered1 it may be feasible to divert a road so that the bridge may be at the best site for the fall4 ,in the case of a railway crossing1 a skew bridge is often necessary4 ,in the case of a road crossing it may be feasible to introduce curves in the road but here also a skew bridge is often necessary4 ,,chapter ,,ii4 ,,the ,,designing ,,of ,a ,,canal4 #a4 ,headworks4--,in the design of head works no very precise rules can be laid down4 ,some general ideas can however be given as to the chief points to be attended to and some general and approximate rules stated4 ,in every case a large scale plan of the river is of course required and also a close examination of it and study of its character4 ,an attempt to forecast its action is then possible4 ,gauge readings for several years and calculations of discharges are of course necessary4 ,if the bed of the river1 in course of time1 rises upstream of the weir or scours downstream of it1 a large amount of protection to the bed and banks will become necessary4 ,some description of headworks and weirs1 with a plan of the headworks of the ,sirhind ,canal1 ,india1 has been given in ,river and ,canal ,engineering1 ,,chapters ,,iv4 and ,x4 ,remarks regarding the collection of information for such works are given in ,,chapter ,,ii4 of the same work4 ,it is also explained how1 by keeping the gates of the under-sluices closed1 a 8pond0 is formed between the divide wall and the canal head so that heavy sand deposits in the pond and does not enter the canal4 ,by closing the canal and opening the under-sluices the deposit is scoured away4 ,the best site for the headworks of a canal depends on the stability and general character of the bed of the river but in deciding between any two proposed sites1 the question of the additional cost of the canal1 if the upper site is adopted1 has to be taken into account4 ,such cost may1 in rugged country1 be considerable4 ,in the case of ,indian perennial canals1 the head is often close to the hills where the river bed is of boulders and shingle and fairly stable1 but it is often at a distance from the hills and in such cases a gradual rise in the bed of the river1 even in the absence of a weir1 is more probable than scour4 ,such a rise may necessitate a raising of the crest of the weir and of the bed of the canal4 ,illustration3 ,,fig4 #e4 ,in the general arrangement of a headworks a great deal depends on local conditions4 ,sometimes the river runs in a fairly straight and defined channel and the weir can then be run straight across it4 ,sometimes1 as in the case of the ,ganges ,canal1 there is a succession of islands and various short weirs are required in the different channels4 ,at the heads of the ,eastern and ,western ,jumna ,canals1 the river1 on issuing from the hills1 widens out 7,fig4 #e47 and the weir is built obliquely and not in a straight line4 ,its crest is higher at the east than at the west side4 ,there are under-sluices at both sides4 ,the upstream end and west side of the island are revetted4 ,the old head of the ,western ,jumna ,canal1 as shown in the figure1 existed long before the advent of the ,british1 and a temporary weir1 made of gabions filled with stones1 was constructed across the river every year during the low water period and swept away during the floods4 ,to have carried the weir along the line shown dotted1 the head of the ,western ,jumna ,canal being of course brought up to it1 would apparently have been feasible and cheaper1 but the off-take would have been in shallow water because of the curve in the river1 and there would have been no current along the face of the head regulator of the canal4 ,the level of the floor of the under-sluices is generally about the same as that of the bed of the canal4 ,the sill--made to exclude shingle and sand as far as possible--of the canal head regulator may be #c feet higher and the crest of the weir #f to #i feet higher4 ,the top of the weir shutters is #a to #be feet above the ,f4,s4 level of the canal which may be #e feet or more above the bed of the canal4 ,if the weir is provided with falling shutters the width of the waterway of the under-sluices may be about th of the width of the waterway of the weir alone1 otherwise about th4 ,in nearly all cases the weir has a flat top and flat slopes both upstream and downstream4 ,in a case where the river bed is of sand1 the depth of water on the crest of the weir in floods may be #ae feet and the velocity #ad or #ae feet per second4 ,the downstream slope of the weir may be about #a in #ae1 and the upstream slope #a in #f4 ,where the river bed is of boulders the velocity may be still higher4 ,the faces of the weir are usually of hammer-dressed stone4 ,a lock for the passage of rafts is added if necessary4 ,unless the banks of the river are high1 it is necessary to construct embankments to prevent the river water1 when headed up by the weir during the floods1 from spilling over the country with possible damage to the canal4 ,if the river has side channels they have to be closed4 ,the stream may also have to be trained1 by means of guide banks or spurs1 so as to remain in one channel and flow past the canal head and not form shoals against it4 ,where the river is unstable1 it may shift its course so as to strike the weir obliquely and this may cause excessive heading up at one side of the weir4 ,in such cases it is usual to divide the weir into bays or sections1 each about #ejj feet long1 by 8divide walls0 running at right angles to the weir4 ,the free-board or height of the masonry walls and tops of embankments above ,h4,f4 ,level is about #e feet4 ,the span of each opening in the under-sluices is generally #bj to #ce feet4 ,the piers may be #e feet thick4 ,it is usual to make each alternate pier project upstream further than the others so that long logs coming down the river during floods1 broadside on1 may be swung round and not be caught and held against the piers4 ,illustration3 ,,fig4 #f4 ,illustration3 ,,fig4 #f;,a4 ,figs4 #f and #f;,a show the headworks of the ,upper ,chenab ,canal now under construction 7,,chapter ,,iv47 ,the site is in a low flat plain1 but no better site could be found4 ,the weir consists of #h bays of #ejj feet each4 ,the crest is #aj feet above the river bed and the falling shutters #f feet high4 ,the slopes are #a in #f and #a in #ae4 ,the bulk of the work is rubble masonry in lime4 ,the lower layer upstream of the crest is of puddle2 upstream of the second line of wells it is rubble masonry in half sand and half lime2 upstream of the lower line of wells it is of dry stone and there is an intermediate layer of rubble masonry in lime with the stones laid flat4 ,below the crest there is a wall of masonry #i feet thick and on the crest there are two strips of ashlar between which the shutters lie when down4 ,the extreme upstream and downstream portions of the bed protection are of dry stone and #d feet thick while next to the weir are concrete blocks #b feet thick resting on dry stone4 ,the width of the crest is #ad feet1 of the weir #adj feet1 of the protection #gj feet upstream and #aaj feet downstream4 ,the guide banks have tops #dj feet wide and #ah and #ad feet above the crest of the weir in the upstream and downstream lengths respectively1 the side slopes being #b to #a and the water slope being covered1 up to ,h4,w4 level1 by dry stone pitching #d feet thick4 ,the left guide bank runs upstream for #c1bej feet from the centre line of the canal and the right #bjjj feet from the line of crest shutters4 ,the under-sluices have #h bays of #ce feet each and the canal head regulator #cf openings of #fe feet each1 the large openings shown in the figure being sub-divided4 ,the crest of the weir is no less than #aj feet above the river bed and the shutters add #f feet to this4 ,the floor of the under-sluices is #d feet higher than the river bed4 ,there is thus ample allowance for a possible rise in the river bed4 #b4 ,the ,contour ,map4--,the contour map1 besides showing the contours of the country to be irrigated and of a strip of country1 even if not to be irrigated1 which will be traversed by the main line1 should show all its main features1 namely3--streams1 drainages1 railways1 roads1 embankments1 reservoirs1 towns1 villages1 habitations1 and the boundaries of woods and cultivated lands4 ,it should also show the highest water levels in all streams or existing canals4 ,a map showing as many as possible of the above features should be obtained and lines of levels run for the contours4 ,in doing this1 the points where the lines of levels cut or pass near to any of the above features or boundary lines1 should be noted4 ,it may be necessary to correct inaccuracies in the plan or to supply defects in it4 ,the greater the trouble taken to do this the less will be the trouble experienced later on4 ,the heights of the contour lines will1 in very flat country1 have eventually to be only #a foot apart4 ,this will necessitate running lines of levels half-a-mile apart at the most1 and preferably #bjjj feet apart1 the pegs in each line being about #ejj feet apart4 ,in less flat country the heights of the contour lines can be further apart than #a foot4 ,whatever distance apart is decided on for them1 the survey should be done once for all4 ,on one of the ,indian canals in flat country1 the lines of levels were at first taken #e miles apart1 the branches roughly aligned and then further surveys made4 ,this led to great expense and delay and the procedure has not been repeated4 ,in making a contour survey1 a base line1 as centrally situated and as long as possible1 should be laid down1 with side lines parallel to it near the boundaries of the tract4 ,the cross lines at half-mile or other intervals should then be laid down4 ,some of them may run out beyond the side lines4 ,circuits of levels should be run along the base line1 the side lines and the two extreme cross lines and be carefully checked4 ,the remaining cross lines should then be levelled4 ,all the levels having been shown on the map the contours should be sketched in4 ,the scale of the map for a large project may be two inches to a mile4 ,if it is likely that the survey will have to be extended1 it will be easier to do this by prolonging the base line and running more cross lines1 than by prolonging each of the cross lines already surveyed4 ,this can be borne in mind when selecting the base line4 #c4 ,alignments and ,discharges4--,on the contour map the proposed alignments of the canal1 branches1 distributaries1 and escapes1 determined after careful consideration of all matters affecting them1 are shown4 ,the tracts to be irrigated by each branch and each distributary are now marked off1 the 8irrigation boundaries0 following approximately the valleys and lines of drainage4 ,any large tracts of land which cannot be irrigated are of course shown and are excluded4 ,forests or other lands which are not to be irrigated should be similarly dealt with1 otherwise confusion is likely to arise later4 ,the commanded area dependent on each distributary is now ascertained from the map4 ,a certain percentage being deducted for scattered unculturable areas the culturable commanded areas are obtained4 ,the proportion to be irrigated 7in ,india in the kharif7 having previously been decided1 the number of acres to be actually irrigated by each distributary is arrived at4 ,the next step is to ascertain the discharges4#i ,a general duty for the whole canal having been estimated by considering the actual figures for other canals the full supply of the canal at its head is arrived at4 7,,chapter ,i1 ,art4 #f74 ,in ,northern ,india it will be the kharif duty and kharif full supply4 ,since some water is lost by absorption in the channels1 the duty of the water on a branch is higher than that of the whole canal based on its head discharge1 and the duty on a distributary is higher still4 ,in designing a canal1 an attempt has to be made to estimate the losses of water in the main canal and branches1 so that the duties of the branches and distributaries may be estimated and the channels designed accordingly4 ,on the ,western ,jumna ,canal the figures were estimated to be as follows3-- ,kharif4 ,rabi4 ,average discharge at canal head 7c4 ft4 per sec47 #cecf #bgee ,duty based on the discharge 7acres7 #ih #ach ,estimated loss of water in canal and branches 7c4 ft4 per sec47 #djj #cjj ,average discharge at distributary head 7c4 ft4 per sec47 #cacf #bdee ,duty based on the discharge 7acres7 #aaa #aed #i ,in this ,article and in the rest of this ,chapter it is assumed that the canal is a ,northern ,indian one4 ,any modifications necessary to suit canals in other countries will readily suggest themselves4 ,the question of duty is one which if not carefully considered1 may cause some confusion4 ,a canal and branches1 having been designed with certain assumed duties and with discharges based on certain values of ,n in ,kutter's co-efficient1 have1 let it be supposed1 been constructed to a greater or less extent4 ,when the time comes for constructing the distributaries1 the engineers concerned may have different ideas1 based on later experience1 as regards the probable duty and the most suitable value of ,n4 ,if they design the distributaries with a higher duty and a lower value of ,n1 it is obvious that they can provide more distributaries than at first designed1 or can increase their lengths4 ,in either case they would provide for an increased commanded area4 ,if they do not do this1 they ought to adhere to the values at first proposed1 thus making the channels larger than1 according to their ideas1 would be necessary4 ,these larger channels will be able to do more irrigation1 by an increase1 not in the commanded area1 but in the proportion of it which is irrigated4 ,any other course would result in the canal carrying more water than could presumably be used by the distributaries4 ,again1 the question how the assumed duty was arrived at may need consideration4 ,it may have been arrived at by taking the duty figures of some existing canal1 based on discharge figures which were the result1 not of observed but of calculated discharges1 and if the calculations were based on a value of ,n which experience has proved to be wrong1 a correction is obviously needed4 ,many mistakes of the kinds indicated above have been made1 not perhaps in the case of a project which has been recently got up and is then quickly carried out in its entirety1 but in one which is carried out slowly or after a long period has elapsed or in one which consists of extensions of an existing system4 ,so great1 however1 is the elasticity of a channel--by which is meant its capacity for adapting itself to varied discharges1 a small change in the depth of water causing a great change in the discharge--and so considerable has been the uncertainty as to the real duty to be expected1 that any mistakes made have not usually resulted in any serious trouble4 ,illustration3 ,,bifurcation ,,at ,,tail ,,of ,,canal4 ,the ,distributaries have ,gates and ,winches4 ,to face p4 #da4 ,it has been stated 7,,chapter ,i1 ,art4 #b7 that it is not desirable to let one channel tail into another4 ,in old canals a distributary used sometimes1 after running parallel to a canal1 to be brought back towards it and tail into it4 ,the advantage of this was that the distributary had not to be made very small towards the tail and that1 if the demand abruptly ceased1 the distributary was not likely to breach4 ,the principle was1 however1 essentially bad4 ,the lower part of the distributary was obviously too near the canal and not centrally situated as regards the irrigated strip4 ,the portion at the extreme tail was superfluous4 ,again1 whatever volume of water was carried through the distributary and back into the canal1 was needlessly detached instead of being kept in bulk4 ,moreover the duty of water on such a distributary cannot be ascertained without a tail gauge and the observation of discharges at the tail4 ,there are similar objections to one distributary tailing into another4 ,each should be separate and distinct4 ,a major distributary is one whose discharge is more than #dj c4 ft4 per second4 ,it may be as much as #bej c4 ft4 per second4 ,a branch1 as soon as it reaches a point where its discharge becomes only #bej c4 ft4 per second should be considered as a major distributary4 ,a minor distributary is one whose discharge is from #h to #dj c4 ft4 per second4 ,a minor distributary is nearly always a branch of a major distributary4 ,there are instances of 8direct minors10 i4e41 minors taking off from canals or branches4 ,such a minor1 unless its discharge is a large fraction of that of the canal which supplies it--and this can seldom be the case--is objectionable because the petty native official who has to see to the regulation of supplies can manipulate the supply easily and without detection1 and the number of persons irrigating from it being small1 he can make private arrangements with them4 ,on the ,sidhnai ,canal there are some half-dozen distributaries each of which had one or two minors which took off close to the head of the distributary4 ,the people who irrigated from the minors managed to get the heads shifted and taken off direct from the canal1 on the ground that1 the water level in the canal being higher than in the distributary1 there would be better command and less silt deposit4 ,the irrigation on all these minors ran up to a figure far in excess of what had been intended1 to the detriment of lands further down the canal4 ,the minor heads have all been retransferred to the distributaries1 the difficulty as to command being got over1 as it should have been at first1 by constructing weirs in the distributaries4 ,the fall in the water surface at the distributary head1 i4e41 the difference between the water level in the canal and that in the distributary downstream of its head but upstream of the weir1 is quite trifling or even inappreciable4 ,in some of the older ,indian canals it was the custom to place the heads of distributaries1 not just above a fall but several hundred feet above it1 the idea being that the distributary then received less silt4 ,this practice has now been discontinued4 ,there is no valid reason for following it4 ,the question whether1 when a channel crosses a road on the skew1 a skew bridge should be constructed or curves introduced into the road or channel1 is one which requires some consideration4 ,as far as possible the lines of channels should be fixed so as to cross important#aj roads on the square or with a small angle of skew4 ,in the case of main canals or branches1 the introduction of special curves is generally out of the question1 but if the road is not straight something can be done by shifting the line one way or the other4 ,in the case of 8major0 distributaries1 curves can to some extent be introduced4 ,in the case of 8minor0 distributaries it is often possible to curve the channel1 with a radius of say #ejj feet1 so that it will cross the road at right angles4 ,there is very little objection to a skew bridge if the angle of skew is not great4 ,the angle of crossing having been made as near to #ij as possible1 the bridge can be made skew though not necessarily so much askew as the road4 ,slight curves can be introduced into the road4 ,when the road is made askew1 a bridge on the square involves at least three considerable curves 7,fig4 #g7 and the taking up of extra land4 ,it also causes1 in perpetuity most likely1 a more or less inconvenient and unsightly arrangement and one which1 in most countries1 would not be tolerated4 ,when the angle of skew is not great1 it is best to introduce no curve at all into the road4 ,in the case of a 8village0 road1 which may be more or less undefined and liable to be shifted1 the difficulty about land may not be great1 but even in this case the angle of crossing should1 if possible1 be kept near to #ij1 especially in the case of minors1 and where curves have to be introduced into the road they should be suitable ones4 ,abrupt angles are not only unsightly but are unfair to the cart drivers4 ,the crossings of village roads by the minors of a certain great modern canal have been stigmatised as 8hideous40 ,indian canals can afford to do work properly4 #aj ,in ,india 8district0 and 8provincial0 roads4 ,illustration3 ,,fig4 #g4 #d4 ,remarks on ,distributaries4--,before a canal system can be properly designed1 it is necessary to determine certain points in connection with the working of the distributaries4 ,a distributary is intended to irrigate a certain kharif area4 ,its average kharif supply is determined from the assumed kharif duty4 ,it generally runs full in the kharif but not always4 ,in a very dry tract such as the ,montgomery district of the ,punjab1 the demand is so great and so steady that a distributary practically runs full through the greater part of the kharif4 ,in such a case the canal or branch must be so designed that it can keep all distributaries full at the same time4 ,its ,f4,s4 discharge will be the sum of all the ,f4,s4 discharges of the distributaries plus the losses of water by absorption4 ,but in other cases1 especially if the rainfall is considerable1 a distributary does not require its full supply1 either all through the kharif or for long at a time4 ,an estimate must then be made of what it will require4 ,it may be estimated that its requirements will be met if1 during the period of greatest demand1 it is closed for two days out of a fortnight and receives full supply for the remaining twelve days4 ,in this case1 since the various distributaries need not all be closed on the same days1 the canal or branch can be so designed that it will carry a full supply equal 7after deducting losses7 to ths of the aggregate full supplies of the distributaries4 ,in other cases the fraction may be ths4 ,it is likely to be lower the greater the rainfall of the district4 ,even in the case when the distributaries run full through nearly the whole of the kharif1 there will be periods when they only run with about ths full supply4 ,if full supply were run at such times1 many of the outlets would discharge more water than was required1 the cultivators would partly close them1 and breaches in the banks of the distributary might result4 ,thus the water level of a distributary must always be so arranged that it will have a good 8command0 when it is running with about three-fourths of the full supply discharge4 ,the water level with ths full supply is generally #e to #ge feet below the full supply level but it should be calculated in each case4 ,generally it will be correct to make the water level1 when full supply is run1 about #a foot above the high ground traversed by the distributary1 excluding any exceptionally high portions of small area4 ,a more exact method is given in ,art4 #i4 ,the greater the proportion of the culturable area which is to be irrigated1 the less should be the area of any high land which is excluded4 ,the ,f4,s4 levels of the distributaries at their off-takes must be settled in accordance with the foregoing remarks1 and these ,f4,s4 levels must be entered on the plan4 ,neglect to thus fix the ,f4,s4 levels of distributaries before designing the canals has frequently led to trouble4 ,the head needed at a bifurcation in order to get the supply into a branch or distributary is always small unless the velocity is high4 ,for a velocity of #c feet per second the head required is only about #af ft41 for #b ft4 per second #a ft4 ,on an ,inundation ,canal which has no weir across the river1 the mean supply downstream of the regulator 7which is built a few miles down the canal lest it should be damaged by the shifting of the river7 is1 as has been mentioned1 about half the full supply4 ,the command in such canals is not generally very good4 ,a distributary can often obtain only mean supply and it should be designed so as to command the country when it is carrying mean supply4 ,a detailed description of ,inundation ,canals in ,northern ,india1 is given in ,punjab ,rivers and ,works4 ,let ,m1 ,f1 m1 f1 be the mean and full supply discharges at the heads of a canal and of an average distributary on it and let the number of distributaries be n4 ,it has been seen 7,chap4 ,i4 ,art4 #f47 that ,m #h;,f about4 ,let k be the proportion of the supply lost by absorption in canal and branches4 ,then n m 7#a - k7 ,m #h 7#a - k7 ,f4 ,if the distributaries all run with full supplies--at the time of greatest demand--for #d days out of #e1 then1 nf #abe 7#a - k7,f f #abe - ---- #aef m #h ,since k depends on the wetted area1 it is not likely to be so great for ,f as for ,m1 but the above gives a general idea of the ratio of the full kharif discharge to the mean kharif discharge4 ,on a large canal the circumstances of the distributaries will not all be similar4 ,some will run full for a greater proportion of their time than others4 ,they can be divided into groups and the ratio of the full to the mean supply calculated for each group4 ,the mean supply is1 as above stated1 obtained from the area to be irrigated1 and the duty as estimated at the distributary head4 ,at one time a system was introduced of making distributaries of large size with the idea of running them for short periods4 ,one reason given for abandoning this arrangement1 was that there was a tendency to run such a distributary for too long4 ,this reason is not very intelligible4 ,it would be applicable to any distributary which was not intended to be run without cessation4 ,the result would be that some other distributary would be kept short of water and this would imply extremely bad management4 ,the chief reason against such a distributary is the greater cost of its construction4 ,it would effect a saving of water4 ,the ratio of the discharge to the wetted area would be high1 though this would be to some extent neutralized by the greater frequency of closures1 since1 when water is admitted to a dry channel1 the absorption is at first great4 ,there would also be some difficulty in the distribution of the water because of the short period for which it would remain open4 ,it will be seen 7,chapter ,,iii4 ,art4 #e71 that it is desirable to open and close always at the same hour of the day4 ,an ordinary distributary might run for #aa days out of #ad4 ,one of double the size could not conveniently be run for #e days4 ,a distributary can always be enlarged if necessary1 but if made too large it is extremely difficult to make it smaller4 ,it was also1 at one time1 usual to make minors1 when there were several on a distributary1 of large capacities so that they ran in turns4 ,the preceding remarks apply to this case4 ,the system has been abandoned4 #e4 ,design of ,canal and ,branches4--,the apportioning of discharges to the various channels having been effected as described in ,art4 #b1 the designing of the canal and branches is proceeded with4 ,rough longitudinal sections of all the lines are prepared by means of the contour map1 the ground levels being shown at intervals of one foot--or whatever the vertical distance between the contours may be--and the horizontal distances obtained from the map by scaling4 ,on these longitudinal sections the lines proposed for the bed and ,f4,s4 levels are shown reach by reach and also the mean velocities and discharges4 ,the laws of silting and scouring and the principles on which channels should be designed are fully gone into in ,river and ,canal ,engineering4 ,it is there explained that1 for a channel of depth ,d1 there is a certain critical velocity1 ,v1 which just prevents the deposit of the silt1 consisting of heavy clay and fine sand1 found in ,indian rivers--this silt enters the canal in such immense quantities that the canal silt clearances would be impossible if much of it was deposited in the channels--that sand of grades heavier than #a may deposit in the head of a canal and well nigh threaten its existence1 that the clear water entering the canal in winter may pick up and carry on some of the sand but that proper steps for preventing the deposit in the canal can be taken at the headworks4 ,this last question has been referred to in ,art4 #a4 ,the following additional rules for designing canals in ,northern ,india are chiefly taken from those given by ,kennedy in the explanatory notes to his ,hydraulic ,diagrams1 which are in use in the ,irrigation ,branch in ,northern ,india4 7#a7 ,near the hills where the bed is of shingle the velocity may exceed ,v4 ,a few other soils will stand #aa ,v4 7#b7 ,in ordinary channels any excess over ,v will give much trouble lower down4 7#c7 ,in the first four or five miles of a distributary1 ,v should be allowed and gradually be reduced to #he ,v at the tail1 the gradient being reduced if convenient1 while a minor or branch distributary should have less than ,v at its off-take and still less at the tail4 ,the sand is drawn off by the outlets and in the lower part of a distributary it is often non-existent4 7#d7 ,if there is efficient silt trapping at the head of the canal any figures arrived at by the preceding rules should be multiplied by #i4 7#e7 ,in the case of a canal having its head far from the hills1 the sand is finer and any figures arrived at as above may be multiplied by1 perhaps1 about #ge1 but further experience is needed to decide this4 7#f7 ,if the soil is very poor1 especially if the depth of water is more than #f or #g feet1 the velocity should be less than ,v--say #i ,v--so as not to cause falling in of the banks4 ,depths of more than #i or #ie feet should1 as far as possible1 be avoided for the same reason4 7#g7 ,at a bifurcation1 one branch channel may have no raised sill1 and1 owing to its smaller depth1 it may draw off no surface water and get an undue share of rolling sand4 ,its velocity should be greater than ,v and that of the other branch be less than ,v4 7#h7 ,at such a bifurcation it may be necessary1 during times of low supply1 to head up the water in the main channel and some silt may temporarily be deposited in it4 ,when the heading up ceases1 the silt is scoured away but it mostly goes into the branch whose bed level is the lower4 ,it is best to design such bifurcations so that the sill levels of the two branches are equal and1 if possible1 so that their bed levels are equal4#aa ,otherwise the channel which is likely to get most silt should have the steeper gradient4 7#i7 ,any existing well established rgime should not be tampered with4 #aa ,appendix ,a in ,river and ,canal ,engineering deals with some instances of fallacies in questions concerning flow in open streams4 ,an extract from it describing a remarkable divide wall recently constructed at the head of the ,gagera branch1 ,lower ,chenab ,canal1 is given in ,appendix ,a of this book4 ,experience shows that in designing ,irrigation ,channels in the plains of ,india in accordance with ,kennedy's figures1 the maximum ratio of bed width to depth of water is as follows3-- ,discharge1 c4 ft4 per second #aj #be #ajj #bjj #ejj #a1jjj ,ratio #ce #d #de #e #f #f ,the actual gradients of the canals generally range from about #a in #h1jjj for a main canal to #a in #b1jjj for the tail of a distributary1 but near the head of a canal where the bed is of boulders and shingle1 the gradient may be as steep as #a in #a1jjj4ab ,the velocity in this last case may be #e feet per second but generally it is not more than #c or #d feet per second in canals and branches1 and #a to #b feet per second in distributaries4 #ab ,on the ,upper ,jhelum ,canal1 #a in #igj4 ,in designing the channels1 ,n1 in ,kutter's co-efficient1 may be taken as #jbbe or #jbj1 according to judgment4 ,for new and smooth channels #jbj is generally correct4 ,a channel generally becomes rougher by use but sometimes it becomes smoother4 ,cases have occurred in which ,n has been found to be #jaf4 ,this question is discussed in ,hydraulics1 ,chap4 ,,vi4 ,the bed width of a canal is reduced1 where a distributary takes off1 in such a way that when the canal and distributary are both running full1 the depth of water in the canal continues to be uniform and the flow to be uniform4 ,when the distributary is closed there is heading up in the canal upstream of the off-take1 but not enough to make any appreciable difference unless the capacity of the distributary is a large fraction of that of the canal and even then no harm is likely to result4 ,the preceding rules and principles being taken into consideration1 the channels are designed4 ,the bed levels1 gradients and depths are so arranged as to give the velocities suited to the soil and to maintain the proper relation of depth to velocity4 ,the bed width is arranged so as to give the proper discharge4 ,the full supply level of the canal and branches has also to be so arranged that it shall be higher1 at each distributary off-take1 than the full supply level of the distributary4 ,it is desirable to be able to give a distributary its full supply even when the canal is low4 ,generally the slope of the country along any line is greater than would be suitable for the bed1 and 8falls0 are introduced4 ,the off-take of a distributary is generally just above a fall and there is generally an ample margin between its ,f4,s4 level and that of the canal4 ,the discharge of the canal during the greater part of the rabi may be only about half the full supply4 ,this discharge should be estimated and the water level corresponding to it calculated and shown on the longitudinal section4 ,if possible the levels should be so arranged that even with its least supply the water level in the canal will enable full supply to be given to a distributary4 ,if this cannot otherwise be managed it may be necessary to construct a regulator in the canal below the head of the distributary so that1 during low supplies1 the water can be headed up4 ,it has been stated in ,river and ,canal ,engineering1 ,chapter ,,iv41 that such heading up1 if temporary1 is not at all likely to cause silt deposit in the canal4 ,the designing of the distributaries is not proceeded with at this stage4 ,since no irrigation is usually done directly from the canal and branches1 they are designed without any particular connection between the level of the water and that of the country traversed4 ,dangerously high embankments are of course avoided as far as possible4 ,the bed is designed at such a level that the excavation and embankment at any place will be1 as nearly as possible1 equal4 ,land in ,india is cheap4 ,when the excavation exceeds the embankment the balance is made into a spoil bank4 ,when the excavation is less than the embankment the balance is got from borrow-pits4 ,the side slopes of channels in excavation are generally #a to #a1 in embankment #a to #a4 ,the sides of channels of small or moderate size usually become about to #a1 or even vertical1 by the deposit of silt on the slopes4 ,this reduction of area is allowed for in the design i4e4 the bed width is so designed that the channel will carry the required discharge1 not with the side slopes as executed1 but when they have become to #a4 ,in large canals however the sides do not always silt up but rather tend to fall in4 ,when this is expected to occur the allowance above described is not made4 ,berms are left so that if any part of the sides fall in1 the bank will not also fall in4 ,the berms also allow of the channel being widened if that ever becomes necessary4 ,type sections are given in ,figs4 #h and #i4 #f4 ,banks and ,roads4--,figs4 #h and #i show the banks and spoil4 ,illustration3 ,,fig4 #h4 ,illustration3 ,,fig4 #i4 ,the scale is #f feet to an inch4 ,the depth of water1 in this particular case1 is #g feet1 and the bank1 excluding the small raised bank1 #b feet above the water4 ,the inside edge of the bank1 where the small raised bank is shown1 is kept parallel to the canal for a considerable distance4 ,its position is got by drawing a line1 shown dotted1 at1 generally1 #a to #a4 ,the embanked part of the slope is actually made at #a to #a1 but the excavation is at #a to #a1 so that a berm is left4 ,the width of this berm of course varies as the depth of digging varies4 ,if there is likely to be much falling in of the sides the berm can be made wider1 the dotted line starting1 not from the edge of the bed1 but from a point further in4 ,on an inundation canal in sandy soil the berm may be #bj feet wide4 ,in figure #h1 the inside slope above the berm is supposed to have silted up to a slope of #a to #a4 ,in cases where it is expected the whole inside slope will silt to to #a the dotted line1 to give the edge of the bank1 can be shifted towards the channel so that the berm at the ground level when the channel is excavated will be very small for the minimum depth of digging4 ,there is no need for the inner edge of the bank to run parallel to the canal for great distances4 ,its position can be shifted whenever suitable and the width of the berm at ground level varied4 ,this prevents the occupation of a needlessly great width of land4 ,it used at one time to be not unusual to make a bank with a berm on the land side1 similar to that formed by the spoil in ,fig4 #h1 but at about the level of full supply in the canal4 ,the principle is not a good one4 ,salient angles are liable to be worn away4 ,if earth has to be added to a bank to strengthen it1 the whole can be widened or the rear slope flattened4 ,the roadway is shown #ah feet wide1 which is nearly the maximum4 ,for the drainage of rain water it has a transverse slope1 away from the canal1 of about #a in #ej4 ,the small raised bank on the canal side is to give safety to wheeled vehicles4 ,it is provided on the patrol bank#ac on main lines and places where there is much traffic or where there is plenty of width of bank to spare4 ,when the ground level is1 for a considerable distance1 above the proper bank level--which is at a fixed height above the ,f4,s4 ,level--so that the road and its side-drain have to be cut out1 much earthwork can be saved by allowing them to be at a higher level and1 in the case at least of the non-patrol road1 giving the road a reduced width4 #ac ,a canal has an unmetalled driving road--called the 8patrol road0 or 8inspection road0 on one bank4 ,this road is reserved for the use of officials4 ,otherwise1 it would soon be cut up and worn away1 and the cost of repairs would be excessive4 ,the patrol road should be on that bank which is1 in the morning 7the time when inspections are usually made7 in the shade of trees planted on the landward side4 ,trees are not usually planted near the water edge as they are sometimes blown down4 ,in ,northern ,india the canals generally flow in a southerly direction1 so that the left bank is best for the patrol bank4 ,on the other bank there is a bridle road which is open to the public4 ,near a rest house--unless there is a bridge actually at the place--the patrol road should be on the same bank as the rest house4 ,it can if necessary cross at the first bridge4 ,frequently there is also on one or both sides of the canal a 8boundary road10 which is open to the public1 along the toe of the outer slope4 ,along a distributary there may be a boundary road on one side4 ,it is generally the only road which can take wheeled traffic1 and in this case it should be reserved for officials unless money is provided to keep it always in repair4 ,officials have to be on tour for weeks or months at a time1 and in all weathers4 ,their baggage carts also have to precede and follow them4 ,anything which facilitates their touring about and seeing things for themselves is1 in ,india1 most desirable4 ,at a watercourse crossing the boundary road along a distributary should be taken by a curved incline up on to the bank and down again4 ,thus not only is the cost of a culvert saved1 but any touring official who is driving obtains a view of the channel which he cannot get from the boundary road4 ,illustration3 ,,fig4 #aj4 ,in shallow digging1 the plan of setting back the banks 7,fig4 #aj7 and letting silt deposit as shown by the dotted lines1 is one which should be followed much oftener than it is4 ,it not only gives eventually a very strong bank1 but it enables the borrow pits1 from which the earth for the banks is got1 to be dug inside the banks4 ,outside borrow pits1 besides being a source of expense1 owing to compensation having to be paid to those in whose land they are dug1 cause great areas of hollows which are not only unsightly1 but are often full of stagnant water and are thus a fruitful source of mosquitoes and malaria4 ,insufficient attention has hitherto been paid to this matter4 ,in designing each reach of a canal or branch1 type cross sections should be drawn out for several different depths of digging1 e4g41 one for very shallow digging1 i4e41 where the bed is little1 if at all1 above the ground level1 one for deep digging where the ground is higher than the water level1 and one for the 8balancing depth10 where the area of the channel excavation is equal to the earth required for the banks4 ,in calculating the earthwork the sectional area of the digging or of the embankment is taken1 whichever is the greater4 ,the proper width and height of bank for any channel depends partly on the maximum depth of water in the channel1 and partly on the discharge4 ,given a depth of water of say #h feet1 a breach will obviously be more disastrous with a great volume of water than with a small volume4 ,the following statement gives some figures suitable to the rather light and friable soils of ,northern ,india1 but the question is largely one of judgment4 ,generally a low and rather wide bank is preferable to a higher and narrower one4 ,if a road1 with or without the small raised bank next the canal1 is required1 special widths can1 of course1 be arranged for4 ,a #ad-;foot bank is required for a driving road4 ---------------------------------------- ---------------- ,top ,width of,height of ,bank ,greatest ,greatest ,bank4 above ,f4 ,s4 ,admissible ,admissible ,discharge4 ,depth of ,water4 ---------------------------------------- ---------------- ,feet4 ,feet4 ,c4 ft4 per sec4 ,feet4 #bj #b #ab1jjj #ab #ah #b #h1jjj #ab #af #b #e1jjj #aa #ad #b #c1jjj #aj #af #ae #b1jjj #i #ad #ae #a1ejj #i #ab #ae #a1bjj #h #aj #ae #a1jjj #g #i #ae #gjj #f #h #ae #ejj #ee #g #ae #djj #e #f #a #cjj #de #e #a #bjj #d #d #a #ajj #ce #c #a #ej #c ---------------------------------------- ---------------- ,the spoil in ,fig4 #h is shown at a different level from the bank proper1 as it should be to give a neat straight edge to the bank4 ,the width of the spoil may vary every chain4 ,in ,fig4 #i the spoil is raised to avoid taking up too much land4 ,the spoil presents the best appearance when its height is kept uniform for as long a length as possible1 the width varying according to necessity1 ,when the height has to be altered1 the change should be made by means of a short ramp4 ,when the spoil is higher than the road1 gaps in it are left at intervals so that rain water can pass away4 ,when the spoil is heavy for a very short length it can1 in order to avoid a short and unsightly heap1 which would result from the adoption of the section shown in ,fig4 #i1 be placed as in ,fig4 #h1 some of it being led askew4 ,the small channel shown outside the bank in ,fig4 #h is a watercourse for enabling trees to be grown4 ,it has1 of course1 to be graded1 and it may be in cutting or in embankment4 ,if any silt clearances of the canal are likely to be necessary1 the watercourse must be set back to allow room for the spoil4 ,such spoil1 if sandy1 is to a large extent washed down or blown away and does not accumulate to anything like the extent that would be expected4#ad ,moreover the spoil can extend onto the watercourse when the trees have grown big1 and no longer need watering4 ,outside the watercourse is shown the boundary road and the land boundary pillar4 ,the small channel in ,fig4 #i is a drain for rain water4 ,it can be used as a plantation watercourse if the water is lifted4 #ad ,this fact has been quoted 7,the ,pioneer ,mail1 8,silt10 #hth ,march1 #aiac7 as showing that the silt supposed to be cleared is not really cleared4 ,this may be the case to some extent1 but shortage of spoil is little proof of it4 ,where there is no spoil1 some extra land1 perhaps #bj feet on either bank1 is usually taken up for getting earth from for repairs4 #g4 ,trial ,lines4--,the proposed lines of channel1 determined as explained in ,art4 #e should next be laid down on the ground4 ,a line should consist of a number of straight portions4 ,the curves should not be put in4 ,trial pits should be dug at intervals4 ,some defects in the line may at once become apparent because the contour map1 owing chiefly to the lines of levels having been taken a considerable distance apart1 is not perfect4 ,a line may pass through a patch of very high or very low ground or too near to some building or other object with which it is desirable not to interfere4 ,alteration may be desirable at a drainage crossing or at the off-take of a branch4 ,the lines should be corrected where necessary4 ,sometimes the corrections may be very considerable4 ,allowance can be made for the alterations which will occur when the curves are laid out4 ,where there is doubt as to which line is the best1 trial pits may be dug to obtain further information regarding the soil4 ,the line should now be levelled1 careful checks being made1 a longitudinal section of it prepared and the proposed bed1 bank and ,f4,s4 level shown4 ,the ground levels ascertained by levelling the line1 are certain to disagree1 to some extent1 with the contour lines4 ,the latter were got only by inference from the levels of points in the survey lines1 and they should be corrected in accordance with the fresh levels now available4 ,if the line does not seem to be the best that can be got1 a fresh line can be marked on the plan and the above procedure repeated4 #h4 ,final ,line and ,estimate4--,as soon as the best line seems to have been found1 a large scale plan of the country along its course should be made by taking bearings or off-sets from points in it to the various objects and noting where the line cuts them4 ,on this plan will be shown the exact alignment1 the curves being put in and the straight portions slightly shifted where necessary so that the line may pass at a proper distance from any buildings or other objects4 ,but before this procedure is carried out1 or while it is being carried out1 the estimate for the work can be prepared from the longitudinal section already taken4 ,such a section is of course amply sufficient for a 8project estimate10 in which only approximate figures are given1 and it is quite near enough for any estimate4 ,in the case of small works which have often to be executed with great promptitude1 lamentable delays have occurred owing to the engineer deferring the preparation of his estimate till he had got the line exactly fixed4 ,moreover there is a chance of the labour being thrown away in case the sanctioning authority directs any change in the alignment to be made4 ,in the case of a large scheme1 a project estimate is prepared4 ,in this the earthwork and the area of land to be occupied are calculated pretty accurately4 ,designs and estimates are also prepared for the headworks and for the chief regulators4 ,for works of which there are to be many of one type--bridges1 falls1 distributary heads and small drainage syphons--the cost is arrived at from lump sum figures1 one drawing of each kind being submitted as a type4 ,the distributaries are approximately estimated at mileage rates4 ,in the case of a small scheme everything is estimated in detail except perhaps the distributaries or some of them4 ,illustration3 ,,canal ,,with ,,bridge ,,and ,,distributary ,,head4 ,the ,head has ,gates and ,winches4 ,to face p4 #fa4 #i4 ,design of a ,distributary4--,a distributary is a canal in miniature and1 like a canal1 it may have branches4 ,it has masonry bridges1 falls and drainage syphons4 ,it has1 as already mentioned1 a masonry regulator at its head4 ,at the off-take of any branch or distributary there is a regulator in the head of the branch4 ,if the branch takes off a large proportion of the water there is a double regulator4 ,a distributary gives off watercourses as a canal gives off distributaries4 ,the watercourses belong to the people and not to ,government and they are cleared and maintained by the people4 ,each watercourse has a masonry head known as an 8outlet0 7,fig4 #aa74 ,the outlet is the point where the water passes from the hands of ,government officials to those of the cultivators4 ,the outlet is of masonry and its opening is not adjustable but is fixed in such a way that its discharge1 when the distributary is full1 bears1 as nearly as can be arranged1 the same ratio to the ,f4,s4 discharge of the distributary as the area intended to be irrigated by the watercourse bears to that intended to be irrigated by the distributary4 ,illustration3 ,,fig4 #aa4 ,the floor of the outlet is level with the bed of the distributary4 ,it thus draws off rolling sand which might otherwise accumulate in the distributary4 ,small outlets are made of earthenware pipes1 about #d feet in diameter1 laid in concrete4 ,two pipes1 or three1 may be laid side by side4 ,if more than three would be required1 a masonry opening is adopted4 ,the discharge through an outlet1 is generally #b to #e c4 feet per second per square foot of outlet area1 and the head #a to #e feet4 ,for the tract of country allotted to any distributary1 a contour map is prepared on a fairly large scale1 say #d inches to a mile4 ,on the map the line is laid down and a rough longitudinal section1 showing the ground level1 is prepared as in the case of a canal4 ,it has already been stated 7,art4 #d7 that a distributary is so designed that its water level1 when three-fourths of the full supply is run1 shall be well above the level of most of the ground along its course4 ,in other words it should have a good command4 ,a good rule is to allow a fall of #e feet from the level of the water in the distributary to that in the watercourse1 a slope of #a in #d1jjj for the water flowing along the watercourse1 and a fall of #c feet for the water at the tail of the watercourse to the level of the ground4 ,this last level is1 like the other ground levels1 taken from the contour map4 ,this procedure1 in short1 consists in making the water level of the watercourse at its head govern that of the distributary1 just as the water level in the distributary at its head was made to govern that in the canal4 ,the enlarged contour map of the distributary area shows1 among other things1 the boundaries of the lands belonging to each village4 ,generally a watercourse supplies water to only one village4 ,when1 however1 a village is far from the distributary1 its watercourse has to pass for a long distance through other villages and it would be wasteful of water to have two separate watercourses4 ,in such cases one watercourse may serve two villages or more4 ,when a village is near to the distributary and its land extends for a long distance parallel to the distributary1 it may have several watercourses for itself alone4 ,a watercourse can generally be most conveniently dug along the boundary line of two villages1 or there may be some other line which the people particularly desire4#ae ,subject to1 or modified by1 these considerations a watercourse is designed to run on high ground like a distributary4 #ae ,they also frequently wish the 8chak0--the area irrigated by a watercourse--so arranged that two men who are 8enemies0 shall not be included in the same 8chak40 ,this condition can be complied with only up to a certain point4 ,arrangements may be modified but not in such a way as to upset the proper rules4 ,illustration3 ,,contour ,,map 7,,part7 ,,and ,,line ,,of ,,distributary4 ,the scale is #a inch to #b miles4 ,the contour lines at #a foot intervals are shown dotted1 the roads by double lines4 ,the line of the distributary1 in order to follow the ridge of the country1 would have gone more to the left of the plan near the village4 ,the shifting of the line to the right brings it nearer to the centre of the irrigated tract--supposed to be the whole area shown--and enables a single bridge to be built at the bifurcation of the two roads4 ,suitable lines for main watercourses are shown in thin firm lines4 ,it is assumed that the command is sufficient to enable the watercourses to run off at the considerable angles shown4 ,to face page #fc ,the great object is to reduce the total length of channels1 i4e41 minors and watercourses4 ,no watercourse can be allowed to run alongside of or near to another4 ,it may run alongside a canal or distributary when really necessary to gain command but not otherwise4 ,the longer the watercourse the larger the chak4 ,the discharge of an outlet may be anything up to #d or #e c4 feet per second4 ,this limits the size of a chak4 ,if a chak is too big it can be split up or a minor can be designed4 ,very small chaks are to be avoided1 but it is difficult to fix a minimum size4 ,the irrigation boundary of the distributary1 as fixed in the project1 is shown on the map but in practice it will not be exactly followed4 ,for various reasons the boundaries of a chak may run somewhat outside it or stop short of it4 ,where a distributary gives off a minor and there is a double regulator1 watercourses should1 as far as possible1 be taken off from one or other of the branch channels and not from upstream of the double regulator4 ,otherwise1 irregularities are likely to occur1 both of the regulators being partially closed at the same time--a thing which is never necessary in legitimate distribution of the supply--in order to head up the water and increase the discharges of the outlets4 ,a watercourse nearly always gives off branches and generally a system of turns is arranged by the farmers among themselves1 each branch in turn taking the whole discharge of the watercourse for a day or part of a day1 the other branches being closed by small dams of earth4 ,to irrigate a field alongside the watercourse a gap is cut in its bank4 ,for fields further away1 smaller channels run off from the watercourses at numerous points4 ,several gaps and several field channels may be in flow at one time1 and there is a dam in the watercourse below the lowest one4 ,occasionally1 on an old canal1 one watercourse crosses another1 the lands irrigated being at different levels1 but such crossings do not often occur in systems of watercourses laid out according to modern methods4 ,they are1 however1 quite legitimate4 ,the lines of the main watercourses are sketched on the map1 their irrigation boundaries shown on it1 and ,f4,s4 discharges allotted to them according to the areas which are to be dependent on them4 ,in order that this may conveniently be done the 8full supply duty0 or 8full supply factor0 for the distributary is obtained4 ,it bears the same ratio to the ordinary duty that the mean supply bears to the full supply4 ,the total of the ,f4,s4 discharges of all the watercourses should1 with an allowance for loss by absorption in the distributary1 be the same as the ,f4,s4 discharge of the distributary4 ,if the results are very discrepant it shows that the sizes of the outlets need revision4 ,possibly they may all be too large4 ,in 8colonization0 schemes where a canal is constructed to irrigate waste lands--which are the property of ,government and which are divided into square blocks and given out to colonists--,government has complete control of the watercourse system1 and can arrange it exactly as desired1 but in other cases landowners often strenuously oppose the passage of watercourses through their lands4 ,compulsory procedure according to legal methods is tedious1 but the practical rule is not to let anyone have water until any watercourses which are to pass through his land have been not only agreed to but constructed4 ,in ordinary cases ,government possesses no power as to the precise line on which a watercourse is dug4 ,it fixes the site of the outlet and assigns certain land to it1 and sketches out the line of the watercourse4 ,if the people choose to alter the line they can do so1 but great alterations in the main watercourses are not generally feasible4 ,the positions of the outlets#af having been settled after discussion with the cultivators1 a table is prepared showing the chainage of the outlets1 the probable head or difference between the ,f4,s4 level of the distributary and of the watercourse1 and the ,f4,s4 discharge4 ,from this the sizes of the outlets are calculated and shown in another column4 ,if the length of the outlet barrel is not more than #e or #f times the diameter--in the case of a barrel whose cross section is not round or square1 the mean diameter--the discharge can be calculated as for a 8short tube10 but if longer the formula for flow in pipes should be used1 allowance being1 of course1 made for the head lost at the entrance4 ,the outlets generally consist at first of wooden 8shoots0 or long tubes1 rectangular in cross section4 ,this is because1 after they have been tested by a year or two years' working1 the sizes nearly always require adjustment and the cultivators often wish to have the site shifted4 #af ,the positions can be slightly altered by the ,engineers for any sufficient reason4 ,illustration3 ,,fig4 #aa4 ,the uncertainty as to the proper size of an outlet is due to several causes4 ,if the command is very good there may be a clear fall from the outlet into the watercourse4 ,in this case the discharge depends only on the depth of water in the distributary1 and is known pretty accurately4 ,but ordinarily the outlet is submerged1 and its discharge depends on the difference between the water levels in the distributary and in the watercourse4 ,the latter level is not fixed4 ,the cultivators can lower it1 to an extent which depends chiefly on the distance of the fields from the distributary1 by deepening or widening the watercourse4 ,in this way the discharge of the watercourse is increased except when a dam is temporarily made in it for the purpose of irrigating any comparatively high land4 ,this uncertainty as to the discharge can in some cases be got over by building a cistern 7,fig4 #aa74 ,this has the same effect as raising the level of the barrel1 the real outlet being no longer submerged1 and the discharge depending on the depth of the crest of the overfall below the water in the distributary4 ,but such cisterns add greatly to the cost of an outlet1 and they can only be adopted when there is good command4 ,a great cause of uncertainty as to the proper size of an outlet is the variability of the duty of the water on the watercourse4 ,the soil may be clayey or sandy1 the watercourse may be short or long1 the crops grown may be ordinary ones or may be chiefly rice1 which requires three or four times as much water as most other crops1 and the cultivators may be careful or the opposite4 ,again1 the people may1 if the outlet gives a plentiful supply1 often keep it closed1 but there is no record of such closures nor would the people admit that they occur4 ,these causes may all operate in one direction--on a whole distributary this cannot happen to the same extent--and thus enormous differences in duty may occur4 ,there is no way of arriving at the proper size for an outlet except trial4 ,observations of the discharges of the outlets are of very limited use4 ,the discharge may vary according to the particular fields being irrigated4 ,observations of discharges will be useful in cases where the people complain1 or when the discharge is obviously much greater or much less than intended and will in such cases enable temporary adjustments to be made1 but by placing a dam in a watercourse and turning the water on to a high field near its head the people can make it appear that the discharge is only a fraction of what it should be4 ,on any distributary there are generally some watercourses which have a poor command1 the head at the outlet being1 say1 #a ft4 or even less4 ,probably the irrigation is a good deal less than it should be4 ,in such cases the rules may be set aside and a liberal size of outlet given4 ,the size may be #b or #c times the calculated size4 ,there is no harm in this4 ,the irrigation cannot increase much4 ,similar cases frequently occur on inundation canals especially near the heads of canals or distributaries4 ,the construction of masonry outlets on a distributary is not usually a final settlement of the matter4 ,further adjustments become necessary4 ,this matter will be dealt with in ,,chapter ,,iii4 ,on the older canals little or insufficient attention was given to the question of the sizes of outlets4 ,the sizes were far too great and1 as long as all the outlets in a distributary remained open1 water could not reach the tail4 ,the distributary used to be divided into two or three reaches and the outlets in the upstream reaches used to be closed periodically4 ,the closures had to be effected through the agency of native subordinates and the system gave rise to corruption on a colossal scale4 ,the tail villages never obtained anything like their proper share of water4 ,the upper villages were over-watered and the soil was often water-logged and damaged4 ,moreover1 even if all concerned had the best intentions1 it was impossible to stop all leakage in the closed outlets1 except by making earthen dams in the watercourses1 and great waste of water resulted from this4 ,the water level of the distributary with full supply1 designed so as to be at least #e ft4 above the water level in the watercourse heads--or to be #a foot above high ground if this simpler plan is adopted--is drawn on the rough longitudinal section and also the line of ,f4,s41 falls being introduced where desirable and the gradients1 ,f4,s4 depths of water and widths of channels being arranged1 just as in the case of a canal1 so as to give the required discharges1 velocities suited to the soil and a suitable ratio of depth to velocity4 ,the bed width of a distributary decreases in whole numbers of feet4 ,the decrease occurs at outlets but not at every outlet4 ,as the channel becomes smaller its velocity becomes less and this necessitates1 according to the laws of silting and scour1 a reduced depth of water4 ,the height and width of the banks in the tail portion of a distributary should be made rather greater than elsewhere--regard being had to the depth and volume of the water--so that breaches may not occur when the demand abruptly slackens4 ,the longitudinal section of a distributary should have horizontal lines for showing the following3 #a4 ,datum #e4 ,draw-off #i4 ,bank width #ac4 ,depth of digging #b4 ,bed gradient #f4 ,f4,s4 discharge#aj4 ,height of #ad4 ,bed level bank #c4 ,village #g4 ,velocity #aa4 ,f4,s4 depth #ae4 ,ground level#ag #d4 ,land width #h4 ,v #ab4 ,bed width #af4 ,chainage#ah ---------------------------------------- --------------------------- #ag ,called 8,natural ,surface0 in ,india4 #ah ,called 8,reduced ,distance0 in ,india4 ,a specimen of a longitudinal section is shown in ,fig4 #ab4 ,it shows only a few of the above items4 ,in practice all would be shown1 large sheets of paper being used with all the lines and titles printed on them4 ,when a distributary is constructed the side slopes are made #a to #a in excavation and #a to #a in embankment4 ,the sides usually silt up till they are to #a or even vertical4 ,the silting up to to #a is1 as in the case of a canal1 allowed for in the designing4 ,the berms are left so that1 if any part of the side falls in1 the bank will not also fall in4 ,they also allow of widening of the channel4 ,the remarks made in ,art4 #f regarding the design of banks1 apply to distributaries1 especially large ones4 ,on a distributary there is seldom much spoil4 ,where there is no spoil1 a strip of land1 outside the bank and #aj feet wide1 can be taken up on either bank from which to obtain earth for repairs4 ,on a minor the width of the strip is sometimes only #e feet4 ,illustration3 ,,fig4 #ab4 ,when a distributary passes through land which is irrigated from wells1 it frequently cuts through the small watercourses which run from the well to the fields4 ,in such cases1 either a syphon or a supplementary well is provided at ,government cost4 ,if several watercourses1 all from the same well1 are cut through1 it is generally possible to combine them for the purpose of the crossing4 ,the wishes of the cultivators in this matter are met as far as possible4 ,the procedure as regards laying out the line on the ground1 digging trial pits1 correcting the line and preparing the estimate are the same as for the case of a canal4 ,illustration3 ,,fig4 #ac4 #aj4 ,best ,system of ,distributaries4--,let ,,ab 7,fig4 #ac7 represent a portion of a distributary1 the irrigation boundary ,,cd being two miles from ,,ab4 ,in order to irrigate a rectangular plot ,,acdb1 the main and branch watercourses would be arranged somewhat as shown by the full and dotted lines respectively4 ,generally1 the whole supply of the main watercourse would be sent in turn down each branch1 the other branches being then dry4 ,the average length open is ,,age4 ,the ends of the branches lie on a line drawn say #bjj feet from the lines ,,bd and ,,dc1 since it is not necessary for the watercourses to extend to the outside edges of the fields4 ,within the field there are small field watercourses which extend to every part of it4 ,by describing three rectangles on ,,ac1 making ,,ab greater than1 equal to and less than ,,ac1 it can be seen that the average length of watercourse open is least--relatively to the area of the block--when ,,ab is equal to ,,ac1 i4e41 when the block served by the watercourse is square as in the figure4 ,if ,,ab is #d times ,,ac1 the average length of watercourse open is increased--relatively to the area of the block--in about the ratio of #c to #b4 ,moderate deviations from a square are of little consequence4 ,suppose two parallel distributaries to be #d miles apart1 each of them being an average ,indian one1 say sixteen miles long with a gradient of one in #d1jjj1 and side slopes of to #a1 the bed width and depth of water at the head being respectively #ace feet and #bi feet1 and at the tail #c feet and #a foot4 ,the discharge of the distributary1 with ,n #jbbe1 will be #gb c4 ft4 per second4 ,the discharge available for the #b mile strip along one bank will be #cf c4 ft4 per second4 ,if the duty is #cjj acres per c4 ft4 the area irrigated in this strip will be #aj1hjj acres1 or #a1cej acres for each of the eight squares like ,,acdb4 ,each main watercourse would then have to discharge #de c4 ft4 per second4 ,supposing its gradient to be #a in #d1jjj and its side slopes to #a and ,n to be #jbbe1 its bed width would be #c feet and depth of water #ade feet4 ,its wet border would be #fc feet1 and its average length #ebhjb #ebhj - #bjj or #ab1edf feet4 ,its wetted area would be #gi1jdj square feet1 and the total wetted area of the #af watercourses--on the two sides of the distributary--would be #a1bfd1fdj square feet4 ,the wetted border of the distributary itself is #aie feet at the head and #e feet at the tail1 average #abbe feet1 and its wetted area is #e1bhj #af #abbe or #a1jcd1hhj square feet4 ,if the distributaries were two miles apart1 there would be twice the number of distributaries1 and each square would be one square mile instead of four4 ,each watercourse would have to discharge #aabe c4 ft4 per second4 ,it would have a bed width of #b ft41 depth of water #h ft41 wet border #ch feet1 length #f1agc feet1 and wetted area #bc1deg feet4 ,the total wetted area of the #fd water courses would be #a1eja1bdh square feet1 or #ah per cent4 more than before4 ,each distributary would discharge #cf c4 ft4 per second1 the bed width and depth at the head being #aj feet and #bbd feet1 and at the tail #b feet and #ge feet4 ,the wet border at the head and tail would be #ade and #ce feet1 mean #i feet1 and the wetted area of the two distributaries would be #a1ebj1fdj square feet or #ej per cent4 more than before4 ,supposing that1 in the case of the larger distributary considered above1 the #b-mile square was considered too large1 and that rectangles #a mile wide were adopted1 so that the watercourses were a mile apart1 their number would be doubled and their length and size reduced4 ,their total wetted area would not be greatly affected1 but the difference in the wetted areas of the two small distributaries as compared with the one large one1 would be the same as before4 ,in practice1 of course1 distributaries are not always parallel1 nor are the blocks of irrigation all squares1 and frequently1 owing to peculiarities in the levels of the ground or the features of the country1 or the boundaries of villages1 it is necessary to align the watercourses in a particular manner1 or to construct more than one watercourse where one would otherwise have sufficed1 but the above calculations show in a general way the advantages of large watercourses and of not placing the distributaries too near together4 ,it is commonly said that a watercourse discharging more than #d or #e c4 ft4 per second is objectionable because the cultivators1 if there are too many of them on one watercourse1 cannot organize themselves in order to work it and keep it in order4 ,this matter is much exaggerated4 ,on the inundation canals of the ,punjab a watercourse often discharges #aj c4 ft4 per second1 and is several miles long and requires heavy clearances1 but the people have no particular difficulty in managing it4 ,kennedy1 a great authority on questions of irrigation1 states that the length of a watercourse may be three miles4 ,this1 if the angle made by a watercourse with the distributary is #de1 gives rather more than two miles as the width of the strip to be irrigated4 ,suppose that a distributary instead of being two miles from each side of the irrigated strip1 ran along one side of it1 and was four miles from the other side4 ,if the block were square1 as before1 the side of a square would be #d miles1 and each watercourse would have to discharge #ah c4 ft4 per second1 which is far too much4 ,the blocks would have to be rectangles1 each being only one mile wide measured parallel to the distributary4 ,it has been already seen that the length of watercourse in this case is greater than when the block is square and each side is two miles4 ,thus centrality in the alignment of the distributary is an advantage4 ,a minor distributary has been defined 7,,chapter ,,ii41 ,art4 #c7 as being one discharging not more than #dj c4 ft4 per second1 but the term has come to be used to designate a branch of a major distributary1 and in that sense it will be used in this article4 ,when the shape of the area commanded by a distributary is such that watercourses exceeding #b miles in length would otherwise be required1 one or more minors are often added4 ,frequently it is a question whether to let some of the watercourses be more than two miles long1 or to construct a minor and thus shorten the watercourses to perhaps only one mile4 ,which method is best has not been definitely settled4 ,it is known that the loss of water in watercourses is heavy1 but if a minor is added the loss in it has to be considered4 ,the loss must be high in any channel in which the ratio of wet border to sectional area is small4 ,the minor also costs money in construction and in maintenance4 ,on the whole the matter1 as far as concerns cost and loss of water1 is1 perhaps1 almost evenly balanced1 but as regards distribution of the supply a system without minors is preferable4 ,the off-take of a minor is generally far from the canal1 i4e41 in a more or less out-of-the-way place1 and it is impossible to see that the regulation is properly carried out4 ,irregularities and corruption are sure to arise4 ,even if the supply is fairly distributed as between the minor and the distributary it is almost certain that the regulator1 if a double one1 will be manipulated for the illegal benefit of outlets in the distributary upstream of the bifurcation4 ,there are sure to be some such outlets not very far distant4 ,in any case each minor adds one1 if not two1 to the already very large number of gauges which have to be entered daily in the sub-divisional officer's register 7,,chapter ,,iii41 ,art4 #c71 and adds also to the mileage of channel to be inspected and maintained4 ,these considerations should1 in many cases1 though of course not in all1 turn the scale against the construction of a minor4 ,at one time it became usual to construct minors even when watercourses more than two miles long would not otherwise have resulted4 ,this custom was condemned some years ago1 and is not likely to be re-established4 ,most of the difficulties just mentioned can1 in the case of a minor which is not too large1 either absolutely or relatively to the main distributary downstream of the off-take1 be got over by making the minor head like a watercourse outlet1 building it up to the proper size1 removing the regulating apparatus and abolishing the reading of the gauge1 but in this case the minor is not likely to be bigger than a large watercourse4 ,such minors should not be constructed1 and any existing ones should1 after the head has been treated as above1 be made over to the people and considered as watercourses4 #aa4 ,outlets4--,the top of the head and tail walls of an outlet are level with the ,f4,s4 levels in the distributary and watercourse respectively4 ,the steps in the head wall enable the cultivators to go down either to stop up the outlet or to remove any obstruction4 ,the stepping is arranged so as to fall inside the side slope ultimately proposed4 ,it is usual1 in some places1 to have the entrance to the 8barrel0 of the outlet made of cast iron4 ,the cast iron pieces are made of various standard sizes4 ,this to some extent prevents the 8barrel0 being built to a wrong size4 ,a discrepancy between the size of the masonry barrel and that of the iron would be noticed1 but if the masonry barrel is built too large the iron head does not always restrict the discharge4 ,the action is the same as in a 8diverging tube0 well known in hydraulics4 ,for sizes up to about #ej or #fj square inches the barrel should be nearly square4 ,for larger sizes the height should exceed the width4 ,up to about #ajj or #abj square inches the width can be kept down to #g or #h inches so that an ordinary brick can be laid across to form the roof4 ,for larger outlets the height can be from #ae to #c times the width1 and the roof can be made of large bricks1 concrete blocks or slabs of stone or of a flat arch of brickwork or by corbelling1 but in this last case there should be two complete courses above the top of the outlet4 ,the less the width the cheaper the roof1 the easier the adjustment of size and the less the tendency to silt deposit during low supplies4 ,if pipes are used they should be laid in concrete4 ,if cast iron head pieces are to be used there should be several sizes of one width and the widths of the masonry outlets should be made to suit these widths4 ,a masonry outlet is not generally built till the watercourse has been sometime in use4 ,the exact position of the outlet should then be so fixed that the watercourse shall run out straight or with a curve and should not be crooked4 ,the width between parapets should be1 for a driving road or one to be made into such1 #aj ft4 7if the bank is wider1 it should be narrowed just at the outlet site7 and for a non-driving road1 #h feet to #c feet according to the ultimate width of the bank4 ,earth backing should be most carefully put in and rammed1 otherwise a breach may occur and the outlet be destroyed4 ,various attempts have been made to provide gates or shutters for outlets4 ,the chief result has been trouble and increased cost4 ,if grooves are made and shutters provided1 the shutters are soon broken or lost by the people4 ,hinged flap shutters are objectionable because they are often closed by boys or by malicious persons or by neighbours who wish to increase the supply in their own outlet4 ,the cultivator1 when he wishes to reduce the supply or to close the outlet1 can easily do this by obstructing the orifice with a piece of wood or an earthenware vessel or a bundle of brushwood or grass4 ,as regards temporary outlets1 wooden outlets if large 7unless made of seasoned wood and therefore costly7 are liable to give great trouble4 ,water escapes round the outside or through the joints4 ,pipes may do well if laid in puddle but are brittle and costly if of large size4 ,the irrigators may interfere both with wooden outlets and pipes and they are liable to be displaced or broken4 ,a temporary outlet1 if small1 can be made of bricks laid in mud4 ,the joints can be pointed with lime mortar4 ,when the outlet is made permanent the same bricks are used again4 ,but all kinds of temporary outlets are liable to give trouble especially in light or sandy soil4 ,there is much to be said in favour of building masonry outlets at the first1 making a barrel only1 i4e41 omitting the head and tail walls and taking the chance of having to alter the size4 ,the alteration is not very expensive4 ,the head and tail walls are built when the size has been finally settled4 ,the adjustment can be made by raising or lowering the roof4 ,this should be done over the whole length of the outlet but lowering can be done temporarily over a length of #c feet at the tail end of the outlet4 ,this can be done even when the distributary is in flow4 ,a reduction over a short length at the upstream end of a barrel does not1 as already remarked1 necessarily reduce the discharge much4 ,on inundation canals the rules regarding outlets have to be modified4 ,great numbers of watercourses take off directly from the canals4 ,in such cases1 especially near the head of a canal1 the ground to be watered is often #e to #h feet above the canal bed and it is wholly unsuitable to place the outlet at bed level4 ,the cost of the tail wall would be excessive4 ,the floor level in such cases must be at about the lowest probable cleared bed level of the watercourse1 say1 in order to be safe1 a foot or half a foot below the usual cleared bed of the watercourse1 so that water need never be prevented from entering the watercourse4 ,the irrigators should be consulted as to the floor level and their wishes be attended to as far as possible4 ,for lift outlets the floor should be at the bed level of the canal or distributary4 ,if this bed is to be raised in the course of remodelling1 the floor should be at the old bed level until the bed has actually been raised1 unless there is a weir which raises the water4 ,it is necessary that lift outlets should work however small the canal supply may be4 ,in a distributary or small canal1 the head wall should be built up to ,f4,s4 level but in a canal with deep water the head wall should reach up to just above the roof of the outlet and be submerged in high supplies4 ,the stepping of the head wall should be set back if the channel is to be widened and should project into the channel if the channel is to be narrowed4 ,the centre line of the channel near the outlet site must always be laid down and the outlet built at right angles to it and also at the correct distance from it4 ,occasionally there is a wide berm1 say #bj ft4 or even #ej ft41 between a channel and its bank4 ,in such a case the outlet should be built to suit the bank4 ,the long open cut is however objectionable because the people clear it and heap the spoil in ,government land4 ,sometimes the bank1 especially if it is crooked1 can be shifted so as to come close to the channel at the outlet site4 ,sometimes the outlets on inundation canals are large4 ,for outlets of more than #be square feet in area1 grooves should be provided so that the cultivators can use a gate if necessary4 #ab4 ,masonry ,works4--,the positions and descriptions of all the masonry works of a proposed canal or distributary are of course shown on the longitudinal section of the channel and from this the discharges and water levels are obtained4 ,the principles of design to be followed#ai for bridges1 weirs1 falls1 regulators and syphons1 are discussed in ,river and ,canal ,engineering4 ,it is mentioned that there is no special reason for making the waterway of a regulator exactly the same as that of the stream1 and that the waterway may be such as to give the maximum velocity considered desirable1 and that the foundations of a bridge should be made so deep that it will be possible to add a floor1 at a lower level than the bed of the stream--with the upstream and downstream pitching sloping up to the bed--so as to increase the waterway and so save pulling down the bridge in case the discharge of the channel is increased4 ,it remains to consider certain points affecting ,irrigation ,canals4 #ai ,so far as concerns their capacity for dealing with flowing water4 ,the span of a bridge1 where there are no piers1 is generally made as shown by the dotted lines in ,figure #ad1 so that the mean width of waterway is the same as that of the channel4 ,the arches1 in ,northern ,india1 used at one time to be #fj as shown by the upper curved line1 but in recent years arches of #ij as shown by the lower curved line1 have frequently been adopted1 the springing of the arch being below the ,f4,s4 level1 so that the stream is somewhat contracted4 ,the #ij arch gives a reduced thickness and height of abutment4 ,it causes increased disturbance of the water1 and this may necessitate more downstream protection4 ,an advantage of having the springing not lower than the ,f4,s4 level is that this admits of a raising of the ,f4,s4 level in case the channel is remodelled1 and this arrangement is still common on distributaries4 ,illustration3 ,,fig4 #ad4 ,when a fall and bridge are combined1 the bridge is placed below the fall as this gives a lower level for the roadway4 ,the side walls of the fall are produced downstream to form those of the bridge4 ,the roads in ,india are generally unfenced and the banks of canals close to bridges1 on both sides of the canal and both above and below the bridge1 are generally more or less worn down by cattle1 which1 when being driven home in the evening and out to graze in the morning1 go down to the stream to drink4 ,in order to prevent this damage the banks are sometimes pitched1 above the bridge as well as below it1 but the cattle generally make a fresh 8ght0 further away4 ,the best plan is to allow a 8ght0 on one bank either above or below the bridge and to protect the other three places4 ,in the ,punjab the widths of roadways between the kerbs and parapets of bridges respectively have been fixed as follows3-- ---------------------------------------- --------- ,,kind ,,of ,,road4 ,,near ,,towns4#bj;,,in ,,the ,,country4#ba ---------------------------------------- ------- ,kerbs4,parapets4 ,kerbs4 ,parapets4 ---------------------------------------- ------- ,provincial #bb #bce #af #age ,district #ah #aie #ad #aee ,village #ad #aee #he #aj ---------------------------------------- ------- #bj ,the figures show the maximum4 ,the general width should be the same as for neighbouring bridges on the same road4 #ba ,the parapets should be whitewashed so as to be visible at night4 ,illustration3 ,,fig4 #ae4 ,fig4 #ae shows a head regulator for a distributary4 ,the scale is #aj feet to an inch4 ,it has a double set of grooves for the insertion of the planks with which the regulation is effected4 ,only one set of grooves is ordinarily used1 but when the distributary has to be closed for silt clearance and all leakage stopped1 both sets of grooves can be used and earth rammed in between the two sets of planks4 ,the floor is shown a foot lower than the bed of the distributary4 ,this reduces the action of the water on the floor1 and enables the bed of the distributary to be lowered if ever the occasion for this should arise4 ,this is a good rule--in spite of the fact that in re-modellings the tendency is for the beds to be raised--for all regulators or bridges1 a raised sill being added 7in regulators7 to reduce the length of the needles or the number of the planks4 ,such sill should1 where needles are to be used1 be fairly wide1 especially if regulation is to be done while the masonry is somewhat new4 ,the distributary shown has a bed width of #aj ft4 ,the span of the two openings in the head might have been four feet each1 but are actually five feet1 and this enables the distributary to be increased in size at any time4 ,the pitched portion of the channel tapers4 ,unless needles are used1 instead of horizontal planks1 spans are not usually greater than #e or #f feet4 ,longer spans would give rise to difficulties in manipulating the planks4 ,sometimes distributary heads are built skew1 but there is seldom or never any good reason for this4 ,a curve can always be introduced below the head to give the alignment the desired direction4#bb ,the small circles shown on the plan are 8bumping posts40 ,on the left is shown a portion of the small raised bank at the edge of the road4 #bb ,the curve can be quite sharp 7see ,,chap4 ,i41 ,art4 #b71 and can be made1 if necessary1 within the length of the pitching4 ,illustration3 ,,fig4 #af4 ,figure #af is a double regulator with needles4 ,the scale is #cj feet to an inch4 ,the spans are #ae feet4 ,the roadway is on arches1 but the regulating platform on steel beams4 ,the needles are seen at the upstream sides of the regulators4 ,they are worked from the platforms to which access is obtained through the gaps in the upstream parapets4 ,the regulating platform should generally be only just clear of the ,f4,s4 level1 and therefore lower than the roadway4 ,illustration3 ,,needle ,,regulator ,,and ,,bridge4 ,needles lying on ,bank4 ,to face p4 #he4 ,frequently the roadway of a bridge or small regulator is carried1 not on arches1 but on steel beams4 ,the railings may be of wood or of gas pipe with the ends plugged1 running through angle iron posts4 ,in the case of such a regulator the roadway is sometimes so light that camels are not allowed to cross over4 ,this causes unnecessary hardship4 ,bridges are not too numerous4 ,if the regulation is done by gates1 both road and platform are carried on arches4 ,the regulators on inundation canals1 and some on perennial canals1 are not strong enough to admit of the flow of water being entirely stopped1 so that the depth of water would be perhaps #aj feet upstream and nil downstream4 ,this might cause the overturning of the piers1 or the formation of streams under the floor4 ,in such cases a maximum permissible heading up is decided on4 ,such orders are1 in ,india1 liable to be lost sight of in course of time1 and they are1 at least on inundation canals1 where sudden emergencies often occur1 hardly reasonable4 ,an engine driver is not told that he must never entirely close his throttle valve4 ,regulators should be so designed that the water can be completely shut off4 ,the following remarks show the chief points in favour of needles and horizontal planks respectively4 ,advantages of ,needles4 ,needles can be placed or removed by one man4 ,needles do not require hooks1 etc41 which are liable to be broken or lost4 ,a needle regulator requires few piers1 and is therefore cheap4 ,water falling over planks throws a strain on the floor4 ,regulation with needles is easy and rapid4 ,a jammed plank1 especially if low down and not horizontal1 may give great trouble4 ,advantages of ,planks4 ,floating rubbish is not liable to collect above the ,regulator because the water flows over the planks4 ,by means of double grooves and earth filling1 leakage can be quite stopped4 ,for large works the advantages are generally with needles1 but for small works1 e4g4 distributary heads and shallow water1 with planks4 ,needles #ad feet long are not too long for trained men4 ,planks are more likely than needles to arrest rolling sand1 and this can be taken into consideration in designing double regulators4 ,see number #h of ,kennedy's rules1 ,article #e4 ,when planks are used there should be two sets of grooves4 ,planks are very suitable for escape heads which have only occasionally to be opened1 earth being filled in between the two sets of planks4 ,illustration3 ,,fig4 #af;,a ,regarding notched falls1 in the case of small distributaries the notches are so narrow that they are extremely liable to be obstructed either accidentally by floating rubbish or wilfully by persons whose outlets are upstream of them4 ,weirs are not open to this objection1 and are frequently adopted4 ,there is not the least chance of their causing any silting worth mentioning4 ,a simple weir if made of the proper height for the ,f4,s4 discharge1 will cause a slight heading up with ths of the ,f4,s4 discharge1 and this unfairly benefits any outlets for a considerable distance upstream of the weir4 ,this difficulty can be got over by making the weir as in ,fig4 #af;,a4 ,illustration3 ,,bridge ,,and ,,notch ,,fall4 ,in this case the usual practice of placing the bridge downstream of the fall has not been followed4 ,the gauge well is seen on the left bank4 ,to face p4 #hg4 ,for cisterns below falls the usual rule for the depth is ,k ,h ,h ,d where ,h is the depth of water in the upstream reach1 and ,d is the difference between the upstream and downstream water levels4 ,another rule for distributaries is ,h ,d ,k ----- #c the length of the cistern being #c ,h and its width the bed width of the channel4 ,at 8incomplete0 falls1 i4e41 where the tail water level is above the crest1 it is not unusual to construct a low-level arch1 which forms a syphon4 ,the object is to allay the surging of the surface water4 ,the question of skew bridges has been dealt with in ,art4 #c4 ,another question is that of the heights of bridges4 ,irrigation channels1 especially the smaller ones1 are very frequently at a high level1 and bridges have ramps which are expensive to make and to maintain1 and are inconvenient4 ,the lowering of distributary bridges in such cases1 so that they become syphons1 or nearly so1 has often been advocated and is frequently desirable4 ,the bed should slope down to the floor and up again4 ,the heading up can be reduced by giving ample waterway1 but it will not be necessary to do this if there is head to spare4 ,the fall in the water surface can be recognised and shown on the longitudinal section4 ,the structure becomes one of the incomplete falls above described4 ,the crown of the arch can1 if desirable1 be kept above ,f4,s4 level1 so that floating rubbish will not accumulate4 ,the width between the parapets of a regulator can be #aj feet in the case of a driving road4 ,it may be less1 according to the width of the bank1 in other cases4 ,the upper layer of the floor of a bridge or regulator is of brick on edge4 ,below this there is a layer of brick laid flat1 and below this1 concrete of a thickness ranging from #e feet to #c feet4 ,the thicknesses of piers range from #ae to #c feet4 ,the bricks used for canal work in ,northern ,india are #aj inches long1 #d inches wide1 and #b inches thick4 ,the thicknesses of walls are about #hc1 #abe1 #ag1 #ba1 #be feet1 and so on4 ,the slopes of ramps should be about #c in #ajj for district roads1 and #e in #ajj for village roads4 ,railings should be provided along the tops of high walls and top of pitching near to public roads or canal patrol roads4 ,bumping posts should be provided for all parapets1 and should not be so placed as to seriously obstruct the roadway4 ,the quarters for the regulating staff should1 when convenient1 be in the fork between the two principal branches4 ,they may be on the bank--with foundations on pillars carried down to ground level--but not in such a position as to obstruct the road or any road likely to be made4 ,rests consisting of two parallel timbers bolted to blocks of masonry reaching up a foot from the ground1 should be provided for the needles or planks4 ,the bolt head should be countersunk so as not to damage the needles and planks when they are hurriedly laid down4 ,when two or more works are close together they should be made to conform1 and the whole site should be considered with reference to a neat and suitable arrangement of works1 ramps and roadways4 ,if an outlet is near to a minor or distributary head the parapets of the two should be in line4 ,if two masonry works of any kind are near together it is often suitable to pitch the intervening space4 ,if there are outlets or distributaries on opposite banks they should be exactly opposite each other4 ,where a road crosses a bridge or regulator1 the bank should be at the same level as the road1 the bank being gradually ramped back to its original level4 ,the space in front of any quarters should have a slight slope for drainage1 but otherwise be at one level and be connected with the road or bank by proper ramps4 ,the berm or bank should be made at the exact level of the top of any pitching or side wall which adjoins it4 ,wing walls are frequently made too short1 so that the earth at their ends forms a steep slope and is worn away1 and the bank or roadway is cut into4 ,the walls should extend to such a point that the earth at their ends cannot assume a slope steeper than the slope of the bank4 ,it is obvious that for every masonry work there should be a large scale site plan#bc showing all roads1 ramps1 and adjoining works1 both existing and proposed roads being shown for some little distance from the work4 #bc ,it is1 or was until recently1 in some parts of ,india1 the custom to omit the preparation of site plans1 and to leave the fixing of the exact site of a work and the arrangement of ramps and other details to the judgment of the assistant engineer who was building it4 ,much unsightly work resulted4 ,a chief engineer in the ,punjab recently issued some orders on the subject4 ,for each kind of masonry work there is usually a type design4 ,a few of its dimensions1 which are fixed1 are marked on it4 ,the other dimensions are variable4 ,it would be a great advantage to add to the design a tabular statement to show how these dimensions should vary under different circumstances4 ,illustration3 ,,fig4 #ag4 ,illustration3 ,,fig4 #ah4 #ac4 ,pitching4 ,the object of pitching upstream of bridges or regulators or downstream of bridges where there may be little or no scouring action1 may be partly to protect the bank from damage by cattle or wear1 or to prevent sandy sides from falling in4 ,in such cases there may be pitching of the sides only1 and it may be of brick on edge laid dry and under this one brick flat resting on rammed ballast 7,fig4 #ag74 ,downstream of regulators or weirs and downstream of bridges if contracted or having piers which cause a rush of water1 especially if the soil is soft1 the side pitching may be as above1 but with the bricks over one-sixth of the area placed on end and projecting for half their length4 ,this 8roughened pitching0 tends somewhat to reduce the eddying4 ,the bed protection should be solid concrete or blocks of concrete or masonry4 ,immediately downstream of regulators or weirs where there is great disturbance1 both side and bed pitching may consist of solid concrete or of concrete or masonry blocks 7,fig4 #ah74 ,illustration3 ,,fig4 #ai4 ,three kinds of toe walls are shown in ,figures #ag1 #ai and #bj4 ,the kind shown in ,fig4 #ai contains1 for a given depth below the bed1 far more masonry than the one shown in ,fig4 #ag4 ,it is also liable to be displaced and broken if scour occurs4 ,illustration3 ,,fig4 #bj4 ,the earth should in all cases be carefully cut to the proper slope1 so that no made earth has to be added4 ,if the slope has already fallen in too much1 well rammed earth should be added4 ,the flat brick and rammed ballast can be varied as the work proceeds1 more being used in soft places and less in hard4 ,in some parts of the ,punjab1 large bricks1 the length1 breadth1 and thickness being about twice the corresponding dimensions of an ordinary brick1 are made1 and are extremely useful and cheap for pitching4 ,where the soil is sandy such bricks can be burned without cracking4 ,sometimes the curtain wall which runs across the bed at the downstream end of the pitching is carried into the banks and built up so as to form a profile wall 7,fig4 #ba74 ,this is not very suitable1 because the pitching of the sides is apt to settle and leave the profile wall standing out4 ,it is better to lay a row of blocks on the slope4 ,if a hole tends to form in the bed downstream of the curtain wall1 blocks of masonry or concrete can be laid and left to take up their own positions 7,fig4 #bb74 ,illustration3 ,,fig4 #ba4 ,illustration3 ,,fig4 #bb4 ,when scour of the bed or sides occurs downstream of pitching1 it is sometimes said that any extension of the pitching downstream is followed by extension of the scour4 ,this may happen if the cross section of the stream downstream of the pitched section has become greater than the pitched section4 ,in this case there is eddying1 due to abrupt enlargement of the stream where the pitching ends4 ,the increased width and lowered bed level 7not counting mere local hollows7 of the stream should be adhered to in the pitching4 ,where the masonry of the regulator ends and the pitching begins1 there will be an abrupt or tapered enlargement1 but the eddies--at very low supplies there may be a fall--cannot do harm4 ,this principle of enlarging the pitched cross section can be followed1 even in a new channel1 if the soil is light and scour is feared1 and for this reason the matter is mentioned in the present ,chapter instead of in ,chapter ,,iii4 ,it was once the custom to splay out the sides of a channel1 downstream of a regulator or weir1 so as to form a sort of pool in which the eddies exhausted themselves1 but this gives curved banks and requires extra land and is not a very convenient or neat arrangement4 ,where scour of the sides is likely to occur1 or has occurred1 immediately downstream of the pitching the latter may be turned in as shown in ,fig4 #bc4 ,illustration3 ,,fig4 #bc4 ,pitching has constantly to be replaced or extended owing1 generally1 to failure to pitch a sufficient length or to ram well the earth under the pitching1 or to use properly rammed ballast or flat brick1 or to give proper bed protection1 or to the use of dry brick pitching when a stronger kind is needed4 ,the side slopes of pitching should be #a to #a4 ,they can be to #a in rare cases1 e4g41 when there is no room for #a to #a1 or in continuation of existing to #a pitching4 ,no absolute rule can be laid down as to the length to be pitched1 but in a ,punjab distributary it is often about #e times the bed width4 #ad4 ,miscellaneous ,items4 ,on ,indian canals the chainage#bd is marked at every thousand feet4 ,five thousand feet is called a 8canal mile40 ,the distance marks are often cast iron slabs1 fixed in a cylindrical block of brickwork about #ba feet in diameter and #ae feet high1 the upper edge being rounded to a radius of #d feet4 ,the wedge-shaped bricks for these blocks are specially moulded4 ,the iron slab should project about eight inches and have about a foot embedded in the brickwork4 #bd ,in ,india1 instead of the simple word 8chainage0 the term 8reduced distance0 is used4 ,it is the distance reduced to a common starting point as levels are reduced to mean sea level4 ,the expression is puzzling to non-professionals and new comers4 ,on a canal having a wide bank the distance mark is put at the outer edge of the patrol bank1 earth being added1 if necessary1 to increase the width4 ,on a distributary with a narrow bank the mark should be on the opposite bank not the patrol bank4 ,to enable the miles to be easily distinguished the masonry block can be sunk only #e foot in the ground1 the others being sunk a foot4 ,in all cases the masonry block rests on a pillar1 #ag feet square1 of bricks laid in mud1 carried down to the ground level4 ,profile walls 7,fig4 #ba1 page #ib7 used occasionally to be built at frequent intervals along a distributary4 ,they will not prevent scour occurring1 if the stream is tending to scour1 unless very close together4 ,such walls are of some use as showing whether the channel is altering1 but they are expensive and have to be altered if1 as often happens1 the channel is remodelled4 ,it is a much better plan to lay down blocks--about #a foot cubes--of masonry or concrete1 along the centre line at every #ejj feet1 with their upper faces level with the bed4 ,if the bed scours they may be displaced but otherwise they are useful not only for showing what silt1 if any1 has deposited1 but for showing the centre line of the channel4 ,without them the centre line is liable to be altered in silt clearances or berm cuttings4 ,to enable a block to be readily found and to be replaced in proper position if displaced1 there should be two small concrete pillars exactly opposite to it and equidistant from it1 one on either bank of the channel4 ,such blocks and pillars may with advantage be placed at quite short intervals on curves4 ,the rest houses for the use of officials on tour are generally at intervals of about #h to #ad miles4 ,there is generally a rest house near to a large regulator and frequently there is one near to a small regulator4 ,this facilitates inspection work and discharge observations and it saves money1 because the house can be looked after by one of the regulating staff4 ,not infrequently the house is placed just too far away from the regulator4 ,similarly if a rest house is near a railway station it should be within a quarter of a mile of it--always provided that this does not bring it too near to villages or huts--and not a mile or more away as is sometimes the case4 ,it is also a mistake to place a rest house off the line of channel unless perhaps when it is on a district road which crosses the channel4 ,,chapter ,,iii4 ,,the ,,working ,,of ,a ,,canal4 #a4 ,preliminary ,remarks4 ,a large canal is under a ,superintending ,engineer and it often constitutes his sole charge4 ,it consists generally of three to five 8divisions10 each under an ,executive ,engineer4 ,a division has two to four subdivisions1 each under a ,subdivisional ,officer4 ,a subdivision is divided1 for purpose of engineering work and maintenance1 into several1 generally three or four1 sections1 each consisting of some #bj miles of canal and some #dj miles of distributary1 and being in charge of a native overseer or suboverseer1 and for purposes of water distribution and revenue1 into a few sections each having1 perhaps1 some #cj1jjj acres of irrigation and being in charge of a native zilladar4 ,as far as possible the boundaries of divisions and subdivisions are co-terminous with those of the branches of the canal4 ,a distributary is always wholly within a subdivision4 ,at every regulator there is a gauge reader1 who1 supplied when necessary with permanent assistants1 sees to the regulation of the supply4 ,if there is a telegraph office at the regulator the telegraph 8signaller0 may have charge of the regulation4 ,the zilladar has a staff of some ten or twelve patwaris1 who record in books the fields watered and who are in touch with the people and know when the demand for water is great1 moderate or small1 and for what kind of crops it is needed4 ,in each division there is generally a ,deputy ,collector who is a native official1 ranking as a ,subdivisional ,officer4 ,his duty is to specially supervise the revenue staff in the whole division4 ,both he and the ,subdivisional ,officer have magisterial powers which are exercised in trying petty cases connected with the canal4 ,along a main canal and its branches there is nearly always a 8canal dak0 or system of conveyance of bags containing correspondence for the officials stationed on the canal or touring along it4 ,along the main line1 and most of the way down the branches1 there is a line of telegraph for the special use of the canal officials4 ,the telegraph offices are at the chief regulators1 with tapping stations1 for the use of officials on tour1 at the rest houses near to which the line runs4 ,however carefully a canal has been designed1 alterations in the channels from silting and scour soon take place and they go on more or less without cessation4 ,in a distributary1 especially if the gradient has of necessity been made somewhat flat1 there is quite likely to be a deposit in the upper reach4 ,the deposit is generally greatest at the head and decreases1 in going downstream1 at a fairly uniform rate4 ,it may extend for half-a-mile or less or more4 ,or a deposit may occur on the sides1 which grow out and contract the channel4 ,this often occurs over a great length of a distributary or even over the whole of it4 ,sometimes a distributary scours its bed1 or the sides may fall in somewhat4 ,clearances of the silt and cutting of the berms are effected at intervals4 ,falling in of the sides may be stopped by means of bushing1 and scour of the bed may be stopped by raising the crest of a fall or by introducing a weir1 but in the meantime the changes cause the discharge tables for the distributary to become more or less erroneous4 ,in many cases silt deposits in the upper part of the distributary during the summer months when the river water is heavily silted and scours away again in the winter1 the rgime of the channel being1 on the whole1 permanent4 ,the changes which occur in the branches and main canal are similar to the above and the remedies adopted are similar4 ,on some of the older canals the scour was so serious that many intermediate weirs had to be constructed4 ,the remarkable silting in the head reach of the ,sirhind ,canal has been described in ,river and ,canal ,engineering1 ,chapter ,v4 ,the remedy consisted in keeping the gates of the under-sluices properly closed so that a pond was formed in which the river silt deposited4 ,when necessary the canal is closed1 the sluices opened1 and the silt scoured away4 ,for a plan of the headworks see fig4 #bd4 ,in working a canal1 it is necessary to arrange so that the water sent down any channel is as nearly as possible in accordance with the demand4 ,the zilladar supplies the ,subdivisional ,officer1 every week or ten days1 with an 8indent0 showing how much water is required in each distributary and the ,subdivisional ,officer makes indents on the subdivision next above4 ,the officer in charge of the headworks thus knows what the demand is4 ,when it is more than the supply available1 the water is dealt out to the various divisions according to rules approved of by the ,superintending ,engineer of the canal4 ,illustration3 ,,fig4 #bd4 ,every gauge-reader has to be given definite instructions as to the gauge reading to be maintained1 until further orders1 in each distributary4 ,at the places where the large branches take off1 the gauge reader is instructed what gauge to maintain in each4 ,in the event of too much water arriving1 he turns the surplus into the escape if there is one4 ,if there is no escape he has usually to raise the gauge readings of the branches by equal amounts4 ,by means of the telegraph1 adjustment is promptly effected at the headworks4 ,it has already been mentioned that rain may cause an abrupt reduction in1 or even cessation of the demand for water4 ,at the same time it increases the actual supply4 ,rain1 or the signs of rain1 in any part of a canal system ought always to be reported to the other parts4 ,owing to changes in the channels1 to fluctuation in the water level of the river1 especially during the night1 to rain or to changes in the temperature and moisture of the air and to lack of continuous attention on the part of the gauge reader1 particularly at night1 there is a constant1 though perhaps small1 fluctuation in the water level in all parts of a canal4 ,it may happen that--owing to enlargement of the channels by scour1 or to other causes--the channels of a canal system are able to carry more water than was intended4 ,in such cases the channels are usually run with as much as they can carry4 ,this may give a lavish supply and a lowered duty1 but it increases the irrigated area4 ,to restrict the supply would cause loss of revenue4 ,sometimes however1 it is restricted to prevent water-logging of the soil4 ,the proper procedure is to extend the canal to other tracts4 ,in ,india the farmers pay for the water1 not according to the volume used1 but according to the area irrigated4 ,different rates per acre are charged for different kinds of crops according to the varying amounts of water which they are known to require4 ,sugarcane1 which is sown in the spring and stands for nearly a year before being cut1 thus extending over the whole of the kharif and most of the rabi1 is assessed at the highest rate4 ,next comes rice which crop1 though only four or five months elapse between its sowing and reaping1 requires a great quantity of water4 ,gardens which receive water all the year round also pay a high rate4 ,other kharif crops are cotton and millet4 ,the chief rabi crops are wheat1 barley and 8gram40 ,every field irrigated is booked by a patwari who is provided with a 8field map0 and 8field book0 for each village 7perhaps #f or #h7 in his beat4 ,the map enables him to recognise at a glance the field in which he is standing4 ,it has a number in the map and1 by referring to this number in the field book1 he finds the area of the field4 ,the patwari is also provided with a 8field register0 in which he books each field which is watered1 showing its area and the kind of crop grown1 the date of booking and the name of the owner and tenant4 ,he goes about entering up all new irrigation and his proceedings are subjected to rigorous check by the zilladar and ,deputy ,collector1 and also by the engineering staff4 ,at the end of the crop the entries are abstracted into a 8demand statement0 in which all the fields cultivated by one person are brought together and1 the proper rates being applied to them1 the sum payable by this person is arrived at4 ,the demand statement goes to the ,collector of the district1 who levies the money and pays it into the ,treasury to the credit of the canal concerned4 ,there is a special charge for any land watered in an 8unauthorised manner40 ,this includes taking water when it was another man's turn1 or taking it from an outlet which has been wilfully enlarged or--in some districts--from another man's outlet even with his consent4 ,the sizes of the outlets are carefully apportioned to the land allotted to them and the area which they irrigate is constantly being looked into in order to see if the size is correct or needs altering4 ,if a man borrows water from another outlet such borrowing may or may not come to light but in any case confusion as to outlet sizes results4 ,the water rates charged for ordinary authorised irrigation are decidedly low4 ,in one district there was a case in which a man1 being unable to get as much water as he needed from his own outlet1 took water for some fields1 by permission1 from a neighbour's outlet4 ,this being found out he was charged for those fields at double the usual rate4 ,he continued regularly to use the water and to pay the double rate4 ,there were several cases of this kind in that one district4 ,since payment for the water is not made according to the volume used1 the cultivators are more or less careless and wasteful in using it4 ,as a rule they over-water the land and frequently damage or spoil it by water-logging4 ,they do not always keep in proper order the banks of the watercourses4 ,the banks often breach and water escapes4 ,any area thus flooded is charged for if it is seen by an official4 ,the engineers have power to close such a watercourse until it is put in order1 but this would cause loss of revenue and is not often done4 ,the real remedy for all this is1 as already stated1 rigid restriction of the supply4 ,the people will then learn--they are already learning--to use water more economically4 ,when the crop in any field or part of a field fails to come to maturity1 the water rate on it is remitted4 ,the failed area is known1 in the ,punjab1 as 8kharba40 ,on some canals the failed areas are liable to be large and an irrigation register1 in order to be complete1 has to show them or1 what is the same thing1 to show both the gross and the net areas1 the latter being the area left after deducting the kharba or remitted area4 #b4 ,gauges and ,regulation4--,in every canal1 branch and major or minor distributary there is a 8head gauge0 below the head regulator4 ,at every double regulator there is a gauge in each branch and also an upstream gauge4 ,these gauges are used for the regulation of the supply4 ,the zeros of the gauges are at the bed levels4 ,tables are prepared showing the discharges corresponding to each gauge reading--except in the case of upstream gauges--at intervals of #a foot4 ,the question often arises whether it is necessary to have a gauge near the tail of a distributary4 ,if the outlets have not been properly adjusted and if water does not reach the tail in proper quantity1 a tail gauge is absolutely essential and its readings should be carefully watched by the ,sub-divisional ,officer4 ,to take no action until complaints arise or until the irrigation returns at the end of the crop show that some one has suffered1 is not correct4 ,when it is known that sufficient water always reaches the tail1 a tail gauge is not necessary4 ,there may be intermediate gauges on a canal or branch or distributary4 ,for convenience of reading they are usually at places where a distributary or minor takes off or where there is a rest house4 ,they serve to show whether the water level at that place alters while that at other places is stationary1 and thus give indications of any changes occurring in the channel4 ,the number of such intermediate gauges should be rigorously kept down4 ,in fact hardly any are necessary4 ,the gauge register which the ,subdivisional ,officer has to inspect daily1 is1 in any case1 voluminous enough4 ,at a double regulator it is never necessary1 except as a very temporary arrangement in case of an accident1 to partially close both channels at once4 ,one or the other should be fully open4 ,the upstream gauge reading shows whether this rule is being adhered to4 ,if the bed levels of all three channels at the regulator are the same1 the reading on one or other of the downstream gauges should be about the same--for the fall in the water passing through an open regulator is generally negligible--as that of the upstream gauge4 ,in other cases the difference in the bed levels has to be taken into account4 ,immediately downstream of the off-take of a channel1 there is1 unless the water flows in without any appreciable fall1 much oscillation of the water4 ,for this reason the gauge is frequently fixed some #ejj feet down the channel4 ,this is anything but a good arrangement4 ,the gauge-reader's quarters are close to the off-take and he will not keep going down to the gauge4 ,moreover an official coming along the main channel cannot see the gauge4 ,the gauge should be close to the head and in a gauge well where oscillations of the water are reduced to very small amounts4 ,the upstream gauge requires no well4#be #be ,for further details as to gauges see ,appendix ,g4 ,all gauges should be observed daily1 in the morning1 and the reports sent by canal dak1 post or wire at the earliest possible moment4 ,this should be rigidly enforced4 ,the register should be posted and laid before the ,subdivisional ,officer daily with the least possible delay4 ,it is only in this way that the ,subdivisional ,officer can keep proper control of the water1 and detect irregularities4 ,sometimes trouble arises owing to the gauge reports not coming in regularly4 ,the suboverseer can be made responsible for seeing to this matter as regards all the gauge readers in his section4 ,gauge readers often reduce the supply in a branch or distributary at night for fear of a rise occurring in the night and causing a breach4 ,this is to save themselves the trouble of watching at night4 ,they are also bribed to tamper with the supply and run more or less in any channel or keep up the supply for a longer or shorter time4 ,all regulation should be rigorously checked by the suboverseer1 zilladar and ,subdivisional ,officer4 ,irregularities can be speedily detected if proper steps are taken such as going to the regulator unexpectedly4 ,the watermarks on the banks can also be seen4 ,if any man is found to have delayed entering a gauge reading in his book or despatching the gauge report it is evidence of an intention to deceive4 ,the suboverseer or zilladar should be required to enter in his note-book all the checks he makes and the ,subdivisional ,officer should see the entries and take suitable steps4 ,there was formerly a general order in the ,punjab that the ,subdivisional ,officer should write the gauge register with his own hand4 ,such an order is not now considered necessary nor has the ,subdivisional ,officer1 now-a-days1 time to comply with it4 ,the register should however be written by the clerk carefully and neatly and not be made over to anyone else4 ,the regulation should usually be so effected that rushes of water in any portion of the channel are avoided1 but if scour occurs in a particular part of the channel it may be necessary to try and obtain slack water there4 ,until it is proved by experience that they are unnecessary1 soundings should be taken periodically downstream of large works4 ,when a branch or escape is closed the leakage should be carefully stopped4 ,the necessary materials should be always kept ready in sufficient quantity4 #c4 ,gauge ,readings and ,discharges4 ,for the head gauge of each distributary and for certain gauges in the canals1 discharge tables1 based on actual observations1 are prepared4 ,if changes occur in the upper part of a channel1 the discharge corresponding to a given gauge reading is altered4 ,one remedy for this is to have a second gauge downstream of the 8silt wedge0 or scoured or narrowed reach4 ,the indents are then made out with reference to the second gauge1 but any slight adjustments due to fluctuation in the water level of the canal1 are effected by means of the head gauge4 ,unless the zilladar and ,subdivisional ,officer are on the alert1 the gauge reader is likely to evade going to the lower gauge every morning1 and to enter fictitious readings for it1 inferring them from the readings of the head gauge4 ,if there are any outlets between the two gauges1 their discharge has to be observed or estimated and added to the discharge of the distributary as entered in the table corresponding to the readings on the second gauge4 ,the above system can be worked with advantage in cases where the distributary bifurcates two or three miles from its off-take4 ,the men in charge of the two regulators can work together1 one of them or an assistant1 going daily from one regulator to the other and back4 ,usually1 however1 the vitiating of the discharge table at the head gauge has to be faced1 and the table to be constantly corrected4 ,it is impossible to frame beforehand any rule or formula which would give a certain correction for a certain depth of silt deposit4 ,moreover1 there might or might not be a contraction of the channel due to deposit on the sides4 ,the usual plan is to observe a discharge some time during each month4 ,if the result is in excess of the tabular discharge1 all the discharges for that month are increased in the same proportion4 ,they can be booked according to the table and totalled1 and the correction applied to the total4 ,discharges of canals and branches at their heads or at the boundaries of divisions1 are observed by the ,subdivisional ,officer about once a month4 ,discharges of distributaries are observed about once a month1 usually by zilladars4 ,they are also to some extent observed by the ,subdivisional ,officer1 but much is left to his discretion4 ,delta is worked out for each distributary month by month1 and also1 of course1 for each crop4 ,thus a general duty 8at distributary heads0 can be obtained1 and may be used in new projects#bf instead of the duty at the canal head1 allowance being made for the water lost by absorption in the canal and branches4 #bf ,see ,,chap4 ,,iv41 ,art4 #b4 ,it cannot be said that these important figures are obtained as carefully as they could be4 ,if the ,subdivisional ,officer personally observed the discharge at each distributary head1 even every other month1 the reliability of the results would be much increased4 ,in addition to this the discharges of canals and branches at the boundaries of subdivisions should be observed and the results compared with the distributary discharges1 so as to show the loss by absorption4 ,at first grave discrepancies among the results would be found1 but they would be reduced as the causes of error became known4 ,for the method of investigating the causes of discrepant discharges see ,river and ,canal ,engineering1 ,,chap4 ,,iii41 ,art4 #e4 ,a specimen of a ,subdivisional ,officer's gauge register is given in table ,i4 ,the zilladar keeps a similar register4 ,the columns headed ,g contain the gauge readings1 those headed ,d the discharges4 ,until some years ago there were no columns for discharges4 ,the daily discharges of the canal and of the branches at their heads--and at intermediate points if they were at the boundaries of divisions--were entered in the ,executive ,engineer's office and the duty was worked out at the end of each crop4 ,the zilladar merely indented for a certain gauge reading at the distributary head1 and the ,subdivisional ,officer could tell pretty nearly what gauge reading he required in the canal at the beginning of his subdivision4 ,since the year #aijj or thereabouts1 the zilladars have been required to learn a good deal about discharges4 ,they have to know how to observe the discharge of a distributary1 and to learn how the discharge of an outlet varies with the head or difference between the upstream and downstream water levels4 ,they are supposed to indent for certain discharges1 and not merely for certain gauge readings4 ,all this knowledge is useful to the zilladars and tends to increase their efficiency1 but a practice of constantly thinking in discharges instead of in gauge readings is unnecessary4 ,if the channels were of all sorts of sizes matters would be different4 ,actually the size of a channel is apportioned to its work1 and the proportion of its full supply which it is carrying at any moment is easily grasped by means of gauge readings alone4 ,,table ,i--,,gauge ,,and ,,discharge ,,register4 ---------------------------------------- ------------------ ,october1 #aiab4 ,main ,line1 ,upper ,bari ,doab ,canal4 ------------------------------------- ,tibri ,regulator ,dhariwal ----------------------------------- ,above ,main ,kasur ,nangal ,canal ,branch ,distributary --------------------------------- ,date4 ,g4,g4,d4,g4,d4 ,g4 ,d4 -------------------------------- #a #dj #ajj #b #dj #ajj #c #dj #ajj 99 99 99 99 99 99 99 99 #bi #db #aaj #cj #db #aaj #ca #db #aaj ---------------------------------------- ----------- ,total #abga #cbee ---------------------------------------- ------------ ,no4 of days in flow #ca #ca ---------------------------------------- ------------ ,average #da #aje ---------------------------------------- ------------ ---------------------------------------- --------------------------- ,october1 #aiab4 ,main ,line1 ,upper ,bari ,doab ,canal4 ---------------------------------------- ------- ,kunjar ,aliwal ,regulator ---------------------------------------- ---- ,kaler ,above,amritsar ,lahore ,escape ,distributary ,branch ,branch ---------------------------------------- ,date4 ,g4 ,d4 ,g4,g4,d4,g4,d4,g4,d4 ---------------------------------------- #a #b #c 99 99 99 99 99 99 99 99 99 99 #bi #cj #ca ---------------------------------------- ------------------- ,total ---------------------------------------- -------------------- ,no4 of days in flow ---------------------------------------- -------------------- ,average ---------------------------------------- -------------------- ,as regards the weekly indents1 the dealing with discharges instead of gauge readings is of little practical value4 ,the zilladar merely knows that on some outlets the demand is great1 on others moderate1 and he judges that the distributary needs say1 #d feet of water1 its full supply gauge being #e feet4 ,he cannot tell how many cubic feet each outlet requires4 ,if he is required to indent in cubic feet per second 7he is not always required to do this7 he probably gets at the discharge from the gauge reading1 and not the gauge reading from the discharge4 ,as regards the general indent made by the ,subdivisional ,officer1 the same remarks apply4 ,he can probably tell what gauge he requires without going into discharges4 ,regarding the working out of delta month by month1 not only are discharges more or less doubtful1 but the area irrigated is seldom correct till near the end of the crop4 ,however1 the figures1 towards the end of a crop1 may be useful4 ,if delta on any distributary is higher than is usual on that distributary1 it may be desirable1 if the supply in the whole canal is short1 to reduce the supply to that distributary somewhat1 but this remedy can be properly applied after the end of the crop by altering the turns 7,art4 #e74 ,any steps in the direction of altering outlets can only be taken after the end of the crop4 ,admitting1 however1 that the working out of delta during the crop is useful1 it can be done by adding up the gauge readings for the month and taking the average reading and the discharge corresponding to it4 ,this is not quite the same as the average of the daily discharges1 but the difference is small1 and there would be a wholesale and most salutary saving in clerical work4 ,all the columns headed ,d could be omitted4 ,the handiness and compactness of the register would be vastly increased4 ,the discharges are only approximately known1 and refinements of procedure are unnecessary4 ,the correction of the discharge table1 by means of observed discharges1 once a month1 can of course be effected without booking the daily discharges4#bg #bg ,there should1 in any case1 be a special place in the gauge register for showing the discharge tables1 with a note of the discharge observations from which the table was framed or in consequence of which it was altered4 ,supposing the columns ,d to be retained the calculations of delta can be made as shown in table ,,ii4 the form being printed in the gauge book4 ,to facilitate the adding up of the discharges a line can be left blank in table ,i4 after each ten days1 and the total for the ten days shown on it4 ,if the column ,d is not retained1 the gauge readings can be added up4 ,the discharge corresponding to the mean gauge reading of the month1 multiplied by the number of days the distributary was in flow1 gives the figure to be entered in column #b of table ,,ii4 ,the final working out of delta crop by crop is of course of the greatest value4 ,the point which needs attention is1 as already remarked1 greater accuracy in the discharges4 ,for reasons which have already been given 7,,chap4 ,i41 ,art4 #e1 and ,,chap4 ,,ii41 ,art4 #i7 the values of delta on different distributaries will never be the same1 but the causes of high values can always be investigated and1 to some extent1 remedied4 ,,table ,,ii4--,,calculation ,,of ,,delta ,,for ,,rabi1 #aiab-ac1 ,,nangal ,,distributary4 ---------------------------------------- ----------------------- ,month4 ,total of ,no4 of days,irrigated ,delta ,remarks4 discharges in flow4 area up up to ---------------------- to date4 date4 ,for ,up to ,for ,up to month4date4month4date4 ---------------------------------------- --------------------- ,acres ,feet ,octo- #cbee #cbee #ca #ca #feaj #aj ber ,novem- #ccij #fcde #bg #eh #ijjj #ada ,closed #c days ber because of breach4 ---------------------------------------- --------------------- #d4 ,registers of ,irrigation and ,outlets4 ,it is obvious that a ,subdivisional ,officer cannot look properly into matters connected with the working of his channels unless he has1 ready to hand1 a register showing1 crop by crop1 the area irrigated by each distributary and each outlet and keeps it posted up to date4 ,in #ahhh the ,chief ,engineer of the ,punjab ,irrigation directed that each ,subdivisional ,officer should keep up ,english registers of irrigation by villages4 ,the order was for years lost sight of4 ,the matter has lately1 in view of certain recent occurrences on a large perennial canal1 again come to notice1 and this most essential factor in the working of a canal is1 it is believed1 receiving attention4 ,as to the precise form which an irrigation register should take1 opinions and practices differ somewhat4 ,in all cases the net irrigated areas should be shown--kharif1 rabi1 and total--and the total remitted area4 ,the areas remitted for kharif and rabi separately may or may not be shown4 ,the net percentage of the commanded culturable area irrigated--total of the two crops--can be shown in red ink and is most useful4#bh ,it enables the general state of affairs on any outlet to be seen at a glance and shows how it compares with other outlets and with the whole distributary4 #bh ,provided that the culturable commanded area is properly shown and is not made to include jungles or other tracts which were never intended to be irrigated4 ,besides the irrigation figures it is necessary to record for each outlet its chainage1 size of barrel#bi and commanded culturable area4 ,in the case of a distributary which has been working for years1 and on which the outlets are undergoing few alterations1 it may be suitable to record the above items in a separate 8outlet register10 and to give in the irrigation register a reference to the page of the outlet register4 ,but even in such a case alterations will have to be made from time to time in the outlet register and there is great danger of its becoming spoilt1 imperfect or unintelligible4 ,in the case of a distributary on which the outlets are undergoing frequent changes1 the items under consideration should be shown crop by crop1 and also the material of the outlet--wood or masonry--and the width and mean height of the barrel4 ,in no other way can the working of the outlet be properly followed and understood4 ,it is probable that this procedure is the best in every case1 i4e41 even when the alterations made are not frequent4 ,by arranging the register as shown in table ,,iii4 the repetition of the entries1 when they undergo no alteration1 is avoided1 only dots having to be made4 #bi ,the sizes of the outlets should be measured by the suboverseer and some checked by the ,subdivisional ,officer and the correct sectional area1 as actually built1 entered4 ,the specimen shows only two outlets on a page1 and covers five years1 but three outlets can easily be shown on a large page1 and the period can be seven years4 ,if there are more than three outlets in the village1 the lowest part of the page shows the total of the page instead of the total of the village1 and the other outlets are shown on the next page1 the grand total for the village coming at the foot4 ,,table ,,iii4--,,register ,,by ,,outlets ,,and ,,villages4 ,distributary 4444444444444444444444444444444444 ---------------------------------------- --------------------------- ,information regarding outlet4 ---------------------------------------- ----- ,dimensions of barrel ,name and ,sectional------------------- description ,year ,chainage,material area of of outlet4 barrel4 ,width ,height 7minimum7 ---------------------------------------- ----------------------- ,register no4 #aijb-jc ,name #aijc-jd #aijd-je ,bank #aije-jf #aijf-jg ,flow or lift ---------------------------------------- ----------------------- ,register no4 #aijb-jc ,name #aijc-jd #aijd-je ,bank #aije-jf #aijf-jg ,flow or lift ---------------------------------------- ----------------------- ,total #aijb-jc of #aijc-jd #aijd-je ,village #aije-jf ,page #aijf-jg ---------------------------------------- ----------------------- ,village 4444444444444444444444444444444444 ---------------------------------------- ---------------------------- ,working of outlet4 ---------------------------------------- --------- ,area in acres4 ,name and ----------------------------------- ,net description ,year ,net irrigated irrigated1 of outlet4 ,commanded ,remitted---------------per cent of culturable ,kharif,rabi,totalculturable4 ---------------------------------------- ----------------------- ,register no4 #aijb-jc ,name #aijc-jd #aijd-je ,bank #aije-jf #aijf-jg ,flow or lift ---------------------------------------- ------------------------- ,register no4 #aijb-jc ,name #aijc-jd #aijd-je ,bank #aije-jf #aijf-jg ,flow or lift ---------------------------------------- ------------------------- ,total #aijb-jc of #aijc-jd #aijd-je ,village #aije-jf ,page #aijf-jg ---------------------------------------- ------------------------- ,all the outlets of the uppermost village on the distributary should be entered1 first1 even though some of them may be downstream of1 and bear serial numbers lower than1 the outlets of the next village4 ,when one outlet irrigates two or three villages the irrigation of the separate villages can be entered on one page in the places usually allotted to outlets1 and the lowest part of the page can show the total for the outlet1 the necessary changes in the headings1 etc4 being made4 ,if any of the villages has other outlets these will appear on another page and the total for the village can also be shown4 ,the village totals should be posted into a second register prepared somewhat as shown in table ,,iv4 and totalled4 ,the totals show the irrigation for the whole distributary4#cj ,if necessary the failed areas can be shown in the register in red ink4 ,if any village is irrigated from two or more distributaries1 each portion of the village should be dealt with as if it was a separate village4 #cj ,very long channels1 e4g4 inundation canals from which direct irrigation takes place1 can be divided into reaches and the irrigation of the reaches dealt with as if they were separate channels4 ,a reach should generally end at a bifurcation or stopdam4 ,in all registers some blank spaces should be left for the insertion of new outlets or new villages4 ,the number of pages to be left will depend on local circumstances1 which should be considered4 ,in case figures are supplied by the revenue authorities and deal only with whole villages1 the details obtained by the canal staff should always be added up and checked with them4 ,similarly the commanded culturable areas for the outlets and villages should be added up and checked with the known total for the distributary4 ,,table ,,iv4--,,abstract ,,of ,,irrigation ,,by ,,villages ,,and ,,channels4 ,canal4444444444444444444444 ,distributary44444444444444 ,from44444444444444444444444 ,to444444444444444444444444 ---------------------------------------- ------------------------- ,name of ,commanded ,net ,areas ,irrigated in ,acres4 ,village4,culturable ,detail4 ---------------------------- ,area 7,acres7 #aijbaijcaijdaijeaijfaijgaijh -#jc -#jd -#je -#jf -#jg -#jh -#ji ---------------------------------------- ------------------- ,kharif ,rabi ,total ,per cent of ,culturable ---------------------------------------- ------------------- ,kharif ,rabi ,total ,per cent of ,culturable ---------------------------------------- ------------------- ,kharif ,rabi ,total ,per cent of ,culturable ---------------------------------------- ------------------- ,total ,the percentages of culturable commanded area irrigated by different outlets will1 as already explained1 always show discrepancies4 ,any special causes of low percentages1 e4g4 a large proportion of rice1 can be briefly noted in the register4 ,on inundation canals1 and some others1 the alignment and chainage are liable to undergo alteration4 ,in such cases it is best to adhere to the original chainage until all the alterations in alignment have been carried out4 #e4 ,distribution of ,supply4 ,the question how the supply of a canal is to be distributed when it is less than the demand1 is not always very simple4 ,suppose that the main canal1 after perhaps giving off several distributaries1 divides1 at one place1 into three branches1 ,a1 ,b1 and ,c1 whose full supply discharges are respectively #b1ejj1 #b1jjj and #a1ejj c4 ft4 per second4 ,suppose that the total discharge reaching the trifurcation is expected to be1 when at the lowest during the crop1 only #b1bjj c4 ft4 per second1 instead of #f1jjj4 ,it would be possible1 supposing the discharge tables to be fairly accurate1 to keep all the channels running with discharges proportionate to their full supplies1 but this would not be suitable4 ,the water levels would not be high enough to enable full supplies to be got into the distributaries1 or at least into some of them4 ,moreover1 the running of low supplies causes much loss by absorption4 ,the plan usually adopted is to give each channel full supply1 or nearly full supply1 in turn1 and for such a number of days that the turn of each branch will recur about once a fortnight1 that being a suitable period having regard to the exigencies of crops1 and having the advantage that the turn of each branch comes on a particular day of the week1 so that everyone concerned1 and especially the irrigating community1 can remember and understand it4 ,table ,v4 shows how the turns in the above case can be arranged4 ,the figures show the discharges4 ,,table ,v4 --------------------------- ,,day4 ,a ,b ,c --------------------------- #a #b1bjj #b #b1bjj #c #b1bjj #d #b1bjj #e #b1bjj #f #b1jjj #bjj #g #b1jjj #bjj #h #b1jjj #bjj #i #b1jjj #bjj #aj #b1jjj #bjj #aa #gjj #a1ejj #ab #gjj #a1ejj #ac #gjj #a1ejj #ad #gjj #a1ejj --------------------------- ,total #ac1hjjaj1jjj #g1jjj ,correct discharge#ab1hjjaj1cjj #g1gjj according to ,full ,supply4 --------------------------- ,the orders given to the gauge readers in these cases are simple1 namely to give each branch full supply in turn1 and to send the rest of the water down the channel next on the list4 ,the number of days allotted to the larger branches are greater than to the smallest because this will probably be simplest in the end1 and also because the number of distributaries on a larger branch is likely to be greater1 and the allotment to the distributaries is thus facilitated somewhat4 ,each branch receives water in one period of consecutive days4 ,any splitting up of the turn would be highly objectionable4 ,it would cause waste of water1 and would give rise to much difficulty in redistributing the supply among its distributaries4 ,each branch receives its residuum turn before it receives its full supply turn4 ,the advantage of this is that water is not let into the channel suddenly4 ,the total supplies of ,a1 ,b and ,c are in the ratio of #ach1 #aj1 and #g1 and not1 as they should be #abh1 #ajc1 and #gg1 but no closer approximation can be got4 ,if the number of days of full supply allotted to each branch is changed1 or if the residuum from ,c is given to ,b1 instead of ,a1 the relative total discharges differ still more from what they should be4 ,if now the total supply is supposed to be increased to #b1gjj c4 ft4 per second1 the discharges are as shown in table ,,vi4 ,,table ,,vi4 ----------------------------- ,,day4 ,a ,b ,c ----------------------------- #a #b1ejj #bjj #b #b1ejj #bjj #c #b1ejj #bjj #d #b1ejj #bjj #e #b1ejj #bjj #f #b1jjj #gjj #g #b1jjj #gjj #h #b1jjj #gjj #i #b1jjj #gjj #aj #b1jjj #gjj #aa #a1bjj #a1ejj #ab #a1bjj #a1ejj #ac #a1bjj #a1ejj #ad #a1bjj #a1ejj ----------------------------- ,total #ag1cjj #aa1jjj #i1ejj ,correct ,discharge4#ae1gjj #ab1fjj #i1ejj ----------------------------- ,considering both the above tables1 ,a always receives more water than its share1 while ,b and ,c on the whole receive too little4 ,considering table ,v4 by itself1 matters might1 perhaps1 be set right by altering the total number of days from #ad to #ac or #ab1 but this1 besides being somewhat objectionable for the reason already given1 might not improve matters when table ,,vi4 came into operation4 ,it is desirable to avoid frequent changes or complicated rules4 ,it is objectionable to make any turn consist of other than a whole number of days4 ,the shifting of the regulator gates is begun at sunrise1 a time when officials are about and can see what is happening4 ,all gauges are read early in the morning1 and those at regulators are read after the regulation has been done and the flow has become steady4 ,if any regulation were done in the evening1 the entry in the gauge register of that day would convey a wrong impression1 and the discharge would be incorrectly booked4 ,moreover1 any system of regularly booking evening as well as morning gauges leads to swelling of the already voluminous gauge register4 ,the best method of adjusting matters is to make slight alterations in the full supply gauges4 ,suppose the normal full supplies in all three branches to be #f feet4 ,when table ,,vi4 is in operation the full supply of ,a can be reduced to about #eh feet4 ,this would give1 during the first #e days1 less water to ,a and more to ,b1 and there is the further advantage that a very small supply1 #bjj c4 ft4 per second1 is not run in any branch4 ,as regards table ,v41 branch ,a never receives full supply4 ,this is a rare case4#ca ,if it were safe1 as it might be1 to run slightly more than full supply in ,c1 this could be done1 and it would increase the supply in ,c during the last four days and reduce that in ,a4 ,otherwise a certain gauge would have to be fixed for ,a which would give it less than #b1bjj c4 ft4 per second during the first #e days1 and the balance would go to branch ,b4 ,similarly1 the gauge of ,b could be slightly reduced1 and this would increase the balance going to ,c4 ,the orders given to the gauge reader are1 as before1 to send the full supply down one channel1 and the balance to the next4 ,the only additional procedure necessary is to inform the gauge reader from time to time what the full supply gauges are4 ,in any case such information has probably to be conveyed to him at times because the channels undergo changes1 and the discharge corresponding to a given gauge also changes4 #ca ,the total discharge1 #b1bjj c4 ft4 per second1 assumed1 is very low compared with the full supply of #f1jjj c4 ft4 per second4 ,when the discharge of the canal exceeds #c1ejj c4 ft4 per second there is1 when ,b and ,c are receiving water1 a second residuum1 which goes to ,a4 ,tables can be worked out for several discharges of the main canal1 but it is the minimum discharge which is the most important factor in the case4 ,the minimum discharge1 or something very near it1 generally lasts through about half the crop1 and it is when the supply is at a minimum that care and justice in the distribution are most needed4 ,the chief objection to the arrangements above described is that the surplus to be sent down one channel or another is sometimes so small that it must be to a great extent wasted4 ,the best means of preventing this is to have the discharge tables1 including one for the main canal at some point higher up than the trifurcation1 constantly corrected4 ,in that case1 it is known under what circumstances a small surplus will occur1 and the orders can be modified so as to prevent its occurrence4 ,the orders will of course be more complicated1 and will have to be dealt with by an engineer and not a gauge reader4 ,the turns1 once satisfactorily arranged1 may go on for years without alteration4 ,they may require altering if any branch is found1 in the course of time1 to be doing worse than or better than the others1 though the correction can probably be made by altering the full supply gauge4 ,the turns of the branches having been arranged1 it remains to settle those of the distributaries4 ,the total available discharge being1 as before1 assumed to be rather more than one-third of the full supply discharge1 each distributary taking off from the main canal1 where it is not possible or not desirable to regulate the height of the water level in the canal1 can be run with full supply for four or five days out of each fortnight1 and then closed4 ,whether it be four days or five may often depend on special circumstances such as whether the distributary is doing well or otherwise4 ,if necessary the full supply can be adjusted4 ,when the canal supply increases the four or five days can be increased4 ,the same principle can be adopted for any distributary whose off-take is in the upper part of a branch1 i4e41 where the branch is many times larger than the distributary1 and where it is not possible or not desirable to regulate the water level of the branch4 ,for a distributary further down the branch1 the turns of branch and distributary can be arranged as explained above for a canal bifurcation4 ,the orders given to the gauge reader are1 as before1 to give the channel whose turn it is1 full supply and to send the balance down the other channel4 ,when the turn of distributary is over it becomes the turn of the branch4 ,the distributary would not be closed if this would cause the full supply in the branch to be exceeded4 ,care must be taken that every distributary receives full supply during part of the time when the branch is receiving full supply4 ,if its turn came only when the branch was receiving a residuum supply1 or rather when the residuum supply was reaching the distributary off-take--for in the case of a distributary whose off-take is far down a long branch the two things are not the same--it might1 in the event of the supply in the main canal falling exceptionally low1 receive no water at all4 ,the time taken by a rise in travelling down a canal is very much the same as that taken by a fall and each takes effect more or less gradually4 ,when a branch receives1 at any point1 a temporary increase in its supply1 owing to the closure of a distributary for1 say1 three days1 there will be a rise lasting for three days at a point further down4 ,the rise will take some time to come to its height1 and some time to die away4 ,there will be about three days from the commencement of the rise to the commencement of the fall1 or from the end of the rise to the end of the fall4 ,if1 either in the main canal or in a branch1 there is any distributary into which full supply cannot be got1 its turn can be increased accordingly4 ,owing to the shortness of the turns1 and to allowance having to be made for the time occupied by rises and falls in travelling down the branch1 the fixing of the turns for distributaries near the tail of the branch requires a good deal of consideration4 ,matters are facilitated by making a sketch 7,fig4 #be7 in which the widths of the channels1 as drawn1 are roughly in proportion to the full supply discharges4 ,if #ad copies of the sketch are made the arrangements for each day can be shown on them1 full supply being shown black and residuum hatched4 ,distributaries would be shown as well as the main channels4 ,illustration3 ,,fig4 #be4 ,the irrigation registers of course show how the irrigation of the different channels is going on from year to year and if changes in the turns become necessary they can be effected4 ,after the water has entered the watercourses the canal officials have nothing to do with its distribution4 ,the people arrange among themselves a system of turns1 each person taking the water for a certain number of 8pahars0--a pahar is a watch of three hours--or fractions of a pahar4 ,the zilladar can however be called in by any person who has a dispute with his neighbour4 ,if the matter is not settled the person aggrieved can lodge a formal complaint and a canal officer then tries the case1 and if necessary punishes the offender4 ,in former days it was usual1 in some places1 for no regular turns to be fixed for the distributaries1 orders being issued regarding them from time to time4 ,the weak point about any such plan is that in the event of the controlling officer delaying1 owing to any accident1 to issue an order1 no one knows what to do4 ,orders were also sometimes issued to zilladars giving them discretionary powers in distribution4 ,no one would now issue such orders4 ,the essential principle is to remove power from the hands of the subordinates4 ,the working of the main channels by turns and the construction of outlets of such a size that they never require closure1 has resulted--in places where such matters are attended to--in the absolute destruction of such power4#cb ,the only way in which a zilladar can injure anyone is to say that water is not in demand4 ,this would however result in damaging the whole of the villages in his charge4 ,he is not likely to do this4 #cb ,in the printed form lately in use in the ,punjab for reports on zilladars1 one of the questions asked is whether 8his arrangements0 for the distribution of water are satisfactory1 as if that was still considered to be the zilladar's business4 ,in case the supply is wholly or partially interrupted owing to a breach or an accident at the headworks1 or other cause1 one particular branch or distributary may lose its turn or part of it4 ,if its loss is not great it may be best to allow the turns to take their usual course1 but otherwise they should be temporarily altered in such a way as to compensate the channels which have suffered4 ,on inundation canals the water at a regulator is sometimes headed up1--all branches being partially closed--in order to give more water to outlets in the upstream reach4 ,there are even some regulators--or rather stop-dams--constructed solely for this purpose at places where there is no bifurcation of the canal or distributary4 ,any such heading up should be planned out beforehand and days for it fixed1 and also the gauge reading4 ,if the water1 without any heading up1 rises to the needful height on the gauge1 nothing has to be done4 ,there are also places on inundation canals where the land is high and is only irrigable during floods4 ,at such places it is usual1 on some canals1 to allow the people to make cuts in the bank when the water attains a certain height4 ,owing to the high level of the country1 nothing in the nature of a breach can occur4 ,in one canal division where the above arrangement was in force1 the people used to send applications to the ,executive ,engineer for leave to cut the banks4 ,this resulted in much delay4 ,a list was prepared showing exactly where the banks might be cut1 the people were informed and the formalities were much reduced4 #f4 ,extensions and ,remodellings4 ,an existing canal or distributary may need remodelling for various reasons1 and in various degrees4 ,if the velocity is too high and the bed has scoured1 or the sides have fallen in1 it may be necessary to raise the crests of falls1 or to construct intermediate weirs1 or to widen the channel and reduce the depth4 ,if the command is not good it may be necessary to regrade the channel4 ,if silt deposit occurs1 the cross-section of the channel may have to be altered1 to give a better relation between ,d and ,v4 ,if there is surplus water1 extensions or enlargements of channels may be desirable and these can sometimes be undertaken to a moderate extent merely by restricting a somewhat too lavish supply to existing distributaries4 ,if the water level is dangerously high it may have to be lowered1 or the banks raised and strengthened4 ,sometimes it is desirable to cut off bends either to shorten the channel and gain command or because the bends are sharp and cause falling in of the banks or1 if numerous1 silting4 ,in all cases the general principles are the same as for entirely new projects1 but certain details require consideration4 ,the distributaries of the older canals were constructed before ,kennedy's laws regarding silting were known1 and it has been necessary to remodel many of them4 ,in some cases the gradient was wrong1 in others the cross-section4#cc ,in some cases a distributary ran in rather low ground1 and it was proposed to abandon it and construct a new one on high ground4 ,it was however pointed out by ,kennedy 7,punjab ,irrigation ,paper ,no4 #aj1 8,remodelling of ,distributaries on old ,canals107 that irrigation had become established along the course of the distributary1 that most of it would remain there and that a new alignment would result in increased length of watercourses4 ,such distributaries have therefore been allowed to remain very much as they were4 #cc ,the difficulty of reducing the size of a channel which is too large is well known and has been discussed in ,river and ,canal ,engineering1 ,chapter ,,viii4 ,it is there explained that a moderate reduction of width can be effected by 8bushing10 but that for great reductions1 groynes or training walls are necessary4 ,when the bed of a distributary is too low it has been suggested that it could be raised by filling in earth in each alternate length of #ejj feet1 and leaving the rest to silt1 but this would be expensive4 ,remodelling should not be considered piecemeal1 but regard should be had to the whole channel4 ,when a distributary is remodelled the outlets should of course be dealt with as well as the channel4 ,the chief thing to consider is not whether the channel as it exists is exactly as it was originally designed to be1 but how it is doing its work and what kind of alteration it needs4 ,even when a simple silt clearance or berm cutting of a channel has to be undertaken1 the work need not always consist in blindly restoring the channel to its original condition4 ,it may be both feasible and desirable to remodel it to a slight extent1 lowering the water for instance in reaches where the outlets draw off very good supplies and thus benefiting less fortunate reaches lower down4 ,the irrigation boundaries of the extended or remodelled channel should as far as possible follow drainages1 but these are not always important or pronounced4 ,the actual irrigation boundaries should be shown and also those of any neighbouring channels of other canals1 and any suitable adjustments should be made4 ,regarding the percentage of area to be irrigated1 it has already been stated that one canal or distributary irrigates a far higher percentage than another4 ,generally when there is a high percentage in any tract1 it is undesirable to cut it down unless it has very recently sprung up to the detriment of other tracts4 ,in some remodelling projects a uniform percentage is taken on the whole area including both new and old irrigation4 ,this plan is suitable when the percentage of old irrigation is not very high4 ,in other cases the old irrigation to be provided for may be taken as the maximum area actually irrigated1 a little being perhaps added for extensions4 ,if the irrigation of considerable areas of jungle tracts is contemplated and if these consist of numerous small patches1 a further percentage can be added for them4 ,if there are large jungle tracts they can of course be dealt with separately and any suitable percentage adopted for them4 ,the percentage for each portion of a remodelling project is not necessarily the same4 ,if the discharge of a channel is increased1 the waterways of bridges may need increasing4 ,this can often be done 7,chapter ,,ii41 ,art4 #ab7 by making a floor at a low level4 ,or the waterway may be allowed to remain small1 the floor being added at the bed level and the bridge then becoming an incomplete fall1 7page #hg74 ,the fall in the water surface1 though small1 can be recognised and shown on the longitudinal section4 ,in remodelling schemes1 the longitudinal section should give all possible information4 ,it should show not only the levels of bed and banks1 but the ,f4,s4 levels 7in blue figures7 above and below all falls or regulators1 and the levels of floors and waterways of bridges4 ,the plan should show all watercourses and the 8chaks0 or areas assigned to them4#cd ,on each chak the actual average irrigation can be shown in blue figures and the proposed irrigation in red4 ,the 8draw-off0 for each proposed outlet can then be shown on the longitudinal section4 ,the area actually irrigated1 as shown on the map1 should in each case be the mean of at least three years1 and if possible of five years4 ,the number of years should be mentioned in a note on the map4 ,cross-sections of channels should always be drawn to natural scale1 and not with the horizontal scale differing from the vertical4 #cd ,the field maps mentioned on page #aja are prepared to a very large scale and show all watercourses4 ,the maps should always be corrected up to date by the patwaris4 ,the chak maps which are on a smaller scale--say #d inches to the mile--can thus be kept correct4 #g4 ,remodelling of outlets4 ,when a channel is remodelled1 the remodelling of the outlets may consist in alterations of the number or sites or in alterations of their sizes4 ,regarding the former1 a map should be prepared showing all watercourses1 chaks and contours4#ce ,on this map new lines for the watercourses can be shown1 the principles enunciated in ,chapter ,,ii41 ,art4 #i1 being generally followed1 but in such a way as to utilise existing watercourses and outlets as far as possible4 ,the work often consists in the abolition of a certain number of watercourses1 when these are too close together and run parallel to one another4 ,there may1 however1 be little gain in amalgamating two such watercourses if they serve two different villages4 ,there is nothing to prevent the people from dividing the watercourse into two as soon as it gets away from the canal1 and they are likely to do this in many cases4 ,when one branch has a flatter slope than the other it would lose command if it took off further down4 ,the people on the steeper branch might not agree to using the flatter one because of silt trouble1 or increased height of embankment4 ,in a new project it is not difficult to get the people to do what is needed1 but when once irrigation has become established it is often difficult to get suitable changes made4 ,the advantages of amalgamating watercourses1 though appreciable1 have been a good deal exaggerated4 ,the chief advantage is gained by reduction in the sizes of outlets4 ,then1 however many branches the watercourse may have1 they can only run in turns and not all together4 ,it may happen that two watercourses1 though taking off near one another1 run in different directions and that the chaks are of suitable shapes and sizes4 ,in such a case the only advantage of amalgamating is that it saves an outlet in the canal bank4 ,no saving in the length of watercourse will be effected because there will be a bifurcation as soon as the watercourse leaves the canal boundary4 ,if both outlets are of suitable design and proper size or require only slight alteration1 both can remain but otherwise amalgamation can be effected4 ,in some cases amalgamation might give a discharge greater than that usually allowed for an outlet but this need form no obstacle4 ,the chief reason for limiting the discharge is the alleged inability of the farmers to manage a large channel4 ,this matter is exaggerated as already stated 7page #gd74 ,in the case under consideration it obviously makes no difference whether there are two watercourses each discharging #e c4 ft4 per second1 or one discharging #aj c4 ft4 per second1 and immediately dividing into two4 ,very small watercourses should1 when possible1 be joined to others but if there is no other near enough they must generally remain1 however small they may be4 #ce ,in small remodelling schemes the lines of existing watercourses show how the country slopes1 and a contour plan is not a necessity4 ,regarding the alterations in sizes of outlets1 whether or not there are alterations in their number and position1 information as to the actual duties on the watercourses should be obtained4 ,the discharge of the watercourses should be observed several times and added up and checked with the discharge of the distributary4 ,the areas irrigated are known from the irrigation register4 ,if the duties are abnormal the causes can be gone into1 and a judgement can be formed as to how far they will remain in existence1 and whether any watercourse is often kept closed4 ,if so the outlet is too large4 ,the duties1 modified so far as may seem desirable1 can be used for calculating the sizes of the remodelled outlets4 ,but alterations of the sizes after a year or two years' working will probably be necessary4 ,the above procedure is also applicable to a case where the old watercourses had no masonry heads but were merely open cuts as on some inundation canals4 ,a common case is that in which the channel is not remodelled--or at least its water level remains very much as before--but merely the outlets are altered in number1 position or size1 or in any or all of these4 ,if the land irrigated by an outlet is high1 the irrigation may be far short of what was expected1 and the size of the outlet may have to be increased or its site shifted1 generally upstream4 ,this is often done at the request of the people1 and at their expense4#cf #cf ,on some of the more modern canals the people are not allowed to pay for outlets1 so that no question of ownership can arise4 ,old outlets should always be removed when superseded by others4 ,otherwise they are apt to be reopened or claims set up regarding them4 ,near the tail of a channel the discharge of an outlet may be an appreciable fraction of that of the channel4 ,in such a case the adjustment of the size of the outlet1 and that of the channel or of any weir or fall in the channel1 should be considered together1 the irrigation on the outlet and that on the channel downstream of it being compared4 ,and similarly as to the sizes of any two or more tail outlets4 ,such outlets are sometimes left without masonry heads on the ground that this injures no one4 ,it may injure an outlet upstream of them by drawing down the water4 ,tail outlets often need constructing or reducing in size to raise the water level in the reach upstream of them4 ,whenever the size of an old outlet is altered the design should be altered if unsuitable4 ,the parapets should be brought into proper line1 the roadway corrected1 the floor level adjusted and any splayed wing walls abolished4 ,if the outlet is skew it should be made square4 ,all this should also be done to all old outlets or heads of minors even if the sizes are correct1 whenever remodelling of outlets on any channel is undertaken4#cg #cg ,wherever an outlet is built or altered1 a template1 made to the exact size of barrel required1 should be supplied to the subordinate in charge of the work4 ,it was stated in ,chapter ,,ii4 that the construction of masonry outlets on a distributary is not usually a final settlement of the matter4 ,in many cases a proper proportion of water does not reach the tail4 ,even in such a case matters have occasionally been left alone1 or the old and pernicious system of closing the upper outlets has been resorted to4 ,in such circumstances the irrigation of a group of tail villages will be found to be less than that of a group higher up1 the people to some extent acquiescing in the old idea that a tail village must be a sufferer4 ,government1 or at least the ,irrigation ,department1 has no particular direct interest in the matter4 ,the total area irrigated1 will probably be very much the same in any case4 ,but an engineer who takes an interest in this part of his work will not allow matters to remain long in the state described4 ,he will1 of his own accord1 adjust the outlets and equalise1 as far as possible1 the irrigated percentages4 ,the people will disturb matters to some extent by enlarging watercourses1 but there is a limit to this and it can be met by an occasional reduction of an outlet4 ,a distributary1 when once its outlets have been carefully adjusted1 attains to something approaching perfection in its working4 ,any excess in the supply is taken partly by the upper outlets but part of it gets to the tail4 ,similarly any deficiency in the supply is distributed over the channel4 ,the outlets which have a poor command and small head are most affected in either case4 ,on the whole they do not lose or gain more than the others4 ,the working of such a distributary causes great satisfaction to the engineer and not the least ingredient in this is the knowledge that he has wholly destroyed the power of his native subordinate4 ,in an inundation canal division in the ,punjab1 some dozen distributaries1 varying in length from #e to #bh miles1 and with discharges ranging up to #cjj c4 feet per second1 were dealt with as above in one season4 ,the engineer in charge being specially desirous that sufficient water should reach the tails1 reduced the sizes of some outlets too much4 ,when an outlet of #a or #b sq4 feet has to be reduced to a small fraction of its size it is not easy to say what the fraction shall be4 ,water reached the tails of all the channels in sufficient quantity1 in some cases in rather more quantity than was necessary4 ,when the irrigation register was examined1 it was found that the general results were entirely satisfactory4 ,in a small proportion of cases outlets had irrigated too little and had to be re-enlarged somewhat4 ,after a second season hardly any changes were needed4 ,when any silt clearance or berm-cutting seemed necessary the irrigation register again came into play4 ,if1 for instance the tail outlets1 as a whole1 were receiving too little water1 enlargement of the upstream reaches was effected with consequent lowering of the water level there4 ,in the case above described the channels flowed for only five months in the year4 ,some of them silted a good deal but as this silting was roughly the same every year1 it did not greatly affect the question of outlet sizes4 ,on a perennial distributary of which the head reach silts during part of the year and scours during the other part1 a proper distribution of supply by adjustment of outlet sizes alone may be more difficult4 ,if the silt was frequently cleared1 this would cause needless expense and interference with irrigation4 ,in cases where the distributary is not run constantly1 something can be done by attending to the regulation4 ,when there is silt in the head reach1 the discharge can be reduced and the period of flow proportionately increased4 ,the lowered water level reduces the supplies of the upper outlets1 and increases the discharges of those lower down4 ,moreover the periodical silting and scour are not always serious4 ,also it is not essential that the supply to each watercourse should be exactly the same every year4 ,there are always good and bad seasons4 ,it is sufficient if a watercourse is not allowed to suffer on the whole1 and is never allowed to suffer much4 ,there is no doubt that it is possible to deal satisfactorily in the above manner with very many distributaries4 ,it is frequently reported that 8difficulty is experienced in getting water to the tail40 ,this is owing to timidity in reducing the sizes of outlets4 ,the suitable plan is to reduce them to such an extent as to cause a proper supply to reach the tail and then1 if necessary to enlarge some4 ,it has been already remarked that only a short length of the barrel need be altered4 ,the cost of this is very small4 ,the real difficulty in the case is not the impossibility of securing good results1 but the impracticability1 in many cases1 of securing the constant attention which the procedure demands4#ch #ch ,see also ,chapter ,v4 ,art #c4 #h4 ,miscellaneous ,items4 ,at the headworks of a canal there is a permanent staff of men who work the gates and look after the works4 ,they assist in discharge observations and in reading the gauges1 and they may have to take soundings in the river to see what changes are taking place4 ,some one is on watch day and night and reads the gauges at frequent intervals4 ,the officer in charge occasionally inspects the works at night without notice4 ,detailed rules regarding the above matters1 and any others that are necessary owing to special local conditions1 are drawn up4 ,sometimes there is difficulty in getting the staff to attend properly to the regulation of the supply in the canal at night4 ,probably some 8tell-tale0 watches would be useful4 ,they would at least show the times at which the men concerned went to the gauges or other points4 ,at the headworks1 and at all important regulators1 a stock of concrete blocks should be kept ready for the execution of any urgent repairs4 ,regarding the ordinary maintenance work on the channels1 details are given in ,appendices ,b and ,c4 ,appendix ,d1 reprinted from ,punjab ,rivers and ,works1 contains rules for watching and protecting any banks or embankments which require it4 ,silt clearances and berm cutting of channels have been mentioned in ,art4 #a4 ,special attention should be given to the accurate ranging of the centre line4 ,otherwise the channel may become crooked4 ,the great defect in the earthwork ordinarily met with in the banks of canals and distributaries is that the clods are not broken4 ,in consequence of this new banks are extremely liable to breach1 and much trouble and expense result4 ,sometimes a dam is thrown across a new distributary1 and the channel upstream of it is gradually filled with water1 the bank being watched and leakages made good4 ,the dam is then shifted to a place further down4 ,in this way the banks are consolidated4 ,when a distributary is closed for silt clearance or other work1 if the head regulator has planks and a double set of grooves1 it is possible to stop all leakage by filling in earth between the two sets of planks and ramming it1 but otherwise it is necessary to construct an earthen dam just below the regulator4 ,upstream of the dam the water1 owing to the leakage through the planks1 gates or needles1 rises to the same level as the water in the canal4 ,native subordinates have a remarkable aptitude for allowing such dams to break while the work in the distributary is in progress or before it is measured4 ,now and then the dam is wilfully cut4 ,the remedy is to make the dam of proper strength--the top should be #h feet wide and a foot above the water1--and to have it watched day and night4 ,at a bend in a channel there is often a silt bank next the convex bank1 and a hollow near the concave bank4 ,the average bed level is probably very much the same as in the straight reaches4 ,removal of the silt bank is unnecessary1 and if removed it quickly forms again4 ,any length of channel in which the depth of silt to be cleared is small1 say #ej foot in a large channel and #dj foot in a small one1 should not be cleared1 provided its length is considerable 7say #a1jjj feet71 and that it is not close to 7say within #c1jjj or #b1jjj feet from7 the head of the channel4 ,estimates should be prepared accordingly1 the shallow digging being struck out4 ,clearing a small depth of silt merely gives contractors a chance of cheating by scraping the bed4 ,if the watercourses at the tail of a distributary are silted1 the people should be pressed to clear them4 ,otherwise there will be heading up of the water of the distributary1 and silt deposit may result4 ,when a channel is scoured1 any regulator in it can be kept partly closed so as to reduce the surface slope in the reach upstream of the regulator and encourage the deposit of silt4 ,a table should1 in such cases1 be drawn up giving the gauge readings to be maintained at the tail of the reach corresponding to given readings at the head4 ,various methods of protecting banks are described in ,river and ,canal ,engineering1 ,chapter ,,vi4 ,the growing of plants on the inner slopes of channels whose sides fall in1 needs special attention4 ,some remarks on this are given in ,punjab ,rivers and ,works1 ,chapter ,,ii41 ,art4 #c4 ,a specification for bushing is given in ,appendix ,e of this volume4 ,a ,subdivisional ,officer generally receives a steady stream of applications from members of the irrigating community regarding--among other matters--outlets or watercourses4 ,generally these applications are made over to the zilladar to be reported on4 ,in a large number of cases the applicant states that the irrigation of his land or 8holding0 is not satisfactory1 or has fallen off1 and sometimes he asks that it may be transferred1 wholly or in part1 to another watercourse which he thinks will give a better supply4 ,in all such cases1 and in some others1 the first requirement is a statement of the irrigation figures4 ,the irrigation register gives only the total for the watercourse4 ,a printed form should be prepared with spaces for showing the name of the distributary1 villages1 watercourses1 holdings and applicants concerned1 and the nature of the application4 ,below this is a form1 prepared somewhat as shown below4 ,when this form is filled in1 the state of affairs can at once be seen and much trouble is saved4 ,the zilladar obtains the figures from the old field registers4 ,the amount of detail required as to the applicant's lands depends on the nature of his application4 ,if it deals with only part of his land the other parts should also be shown4 ,he may for instance be giving a disproportionate share of water to one part4 ,if a transfer to another watercourse is asked for1 the figures for that watercourse are also required4 ---------------------------------------- --------------------------- ,areas in ,acres4 ,applicant's ,holding4 ,total of,total of ------------------------------- ,water- ,distrib- ,total4 course4 utary4 ---------------------------------------- ------------------------ ,culturable commanded4 ,net #ai444-ai444 irri-#ai444-ai444 gated#ai444-ai444 ---------------------------------------- ------------------------ ,total of #c years ---------------------------------------- ------------------------ ,average ---------------------------------------- ------------------------ ,per cent4 of culturable commanded ---------------------------------------- ------------------------ ,if an application refers to a whole watercourse1 the ,subdivisional ,officer can frequently1 with the aid of an irrigation register and a set of chak maps1 both kept up to date1 dispose personally of the case4 ,a good plan is to settle cases when on tour near the place concerned1 the applicant and the zilladar being present as well as any other persons concerned4 ,a certain number of cases have to come up again on the following tour1 but all are settled in less time than is occupied if the papers go up and down between the ,subdivisional ,officer and the zilladar1 the 8file0 of papers in any particular case being constantly swollen by reminders from the applicant4#ci ,moreover1 the applicants know that their views are known to the ,subdivisional ,officer4 ,if the outlets on a channel need a general remodelling1 such applications as those under consideration receive attention in connection with the scheme4 ,otherwise all the applications concerning one distributary can be considered together4 ,if1 however1 a case is pressing1 or the steps to be taken obvious1 it can be settled without reference to any other case4 #ci ,the plan of personal settlement is distasteful not only to the subordinates1 but to the munshi who has charge of the 8vernacular files40 ,ordinarily he can delay a case1 or manipulate it to some extent4 ,the general arrangements for the 8revenue0 work or assessment of water rates have been stated in ,art4 #a4 ,in the ,punjab the remissions for failed crops are a source of trouble4 ,in some districts the failed areas are small1 and no particular trouble arises1 but in other districts such areas are often very large4 ,on perennial canals the crop inspection is done by the zilladars1 on most of the inundation canals by the subordinates of the ,district ,magistrate4#dj ,in both cases the amount of labour involved is enormous1 and the corruption to which the system gives rise is also enormous4 ,in the case of the inundation canals the superior staff of the ,district ,magistrate nominally make checks1 but the time at their disposal is wholly inadequate4 ,in the case of the perennial canals the ,canal ,engineers are able to exercise considerable checks1 but nothing like enough4 ,in fact the state of a crop and the proportion of the charge on it which should be remitted is a difficult thing to judge1 even if the subordinates were without guile4 ,it is understood that a new and statesmanlike system is now to be introduced1 the ,district ,magistrate deciding1 in consultation with the ,executive ,engineer1 whether the season is such as to call for any general remission for each kind of crop1 and1 if so1 to what extent4 ,the proportion to be remitted in that crop is then to be fixed1 and it is to be the same for every one4 #dj ,officially called the 8,collector0 in some provinces1 and 8,deputy ,commissioner0 in others4 ,it has been mentioned that some irrigation is effected by lift4 ,the simplest form of lift is a horizontal pole which rests1 not far from its thick end1 on a support4 ,from its thick end is suspended a bucket1 and from its thin end a weight4 ,a man lifts the thin end so that the bucket then dips into the water and is filled4 ,pulling down the thin end he raises the bucket and empties it4 ,a greatly improved lifting apparatus is the ,persian wheel which is vertical and has slung from it1 like the buckets of a dredger but moving vertically1 a number of earthen jars1 which scoop up the water4 ,as each jar passes over the top of the wheel it assumes a horizontal position1 discharges its water into a shoot1 and descends in an inverted position4 ,the wheel is moved by a simple cog-wheel arrangement actuated by a bullock which is driven round and round in a circular track4 ,the ,persian wheel is used for lifts of any height4 ,the lift from a canal watercourse is a few feet1 that from a well may be #ej feet or more4 ,most persons consider that a system of charging for water by volume would be a very great advance on present methods4 ,it has been said that if the water were wasted it would be difficult for the cultivators to bring home the responsibility to any individual4 ,this objection does not seem to have great force4 ,every individual would have a direct interest in economising the water1 and any cultivator who was habitually careless would soon be detected by the others4 ,in all probability the result would be a great improvement in the duty of the water4 ,but the justice of any very rigid system of charging by volume is somewhat doubtful4 ,the great difference in the duty of water on different watercourses has been mentioned more than once4 ,many of the causes of this are beyond the control of the farmers1 and it would probably be necessary to charge reduced rates to some of them4 ,,chapter ,,iv4 ,,the ,,punjab ,,triple ,,canal ,,project4#da #da ,see ,report on the ,project ,estimates of the ,upper ,jhelum1 ,upper ,chenab1 and ,lower ,bari ,doab ,canals4 ,illustration3 ,,fig4 #bf4 #a4 ,general ,description4 ,fig4 #bf shows part of the ,punjab4 ,the areas marked ,l4,j41 ,l4,c41 ,u4,b4,d41 and ,s4,c4 are already irrigated by the ,lower ,jhelum1 ,lower ,chenab1 ,upper ,bari ,doab#db and ,sirhind ,canals4 ,the areas which it is considered very desirable to irrigate1 and which are provided for in the ,triple ,canal ,project1 are marked ,u4,j41 ,u4,c41 and ,l4,b4,d41 and the new canals are shown by dotted lines4 ,other areas needing irrigation lie on the left bank of the lower part of the ,sutlej1 partly in ,british territory and partly in ,bahawalpur ,state1 and one area1#dc of scant rainfall and subject to occasional famine1 lies immediately ,south of the ,sirhind ,canal tract4 ,there is also a very large area between the ,indus and the ,jhelum1 and it has been proposed to irrigate it from the ,indus1 but on account of the presence of sand-hills the project is not likely to be so useful as others1 and it is held in abeyance4 ,perhaps a small canal may be constructed1 as a tentative measure1 to irrigate part of the tract4 #db ,doab means 8two waters10 or the tract between two rivers4 ,the names of the three ,doabs under consideration are formed from those of the rivers4 ,they are called the ,jech 7,jhelum-,chenab71 ,rechna 7,ravi-,chenab71 and ,bari 7,beas-,ravi7 ,doabs4 #dc ,it would be very expensive to bring water for this tract from the ,beas and across the ,sutlej4 ,the winter discharges of the rivers 7available for the rabi crop7 after the existing irrigation has been supplied1 are as follows3 ,indus1 #i1dcd c4 feet per second 7minimum7 ,jhelum1 #f1hjj 7average7 ,chenab1 ,nil ,ravi1 ,nil ,beas1 #d1jjj 7minimum7 ,sutlej1 ,nil ,in summer all the rivers have discharges 7available for the kharif crop7 far exceeding any requirements4 ,it was at one time proposed to supply the ,lower ,bari ,doab ,canal from near the junction of the ,beas and ,sutlej1 and a project for this was prepared1 but before it was sanctioned a proposal was put forward to convey the surplus water of the ,jhelum eastward across the ,chenab and ,ravi4 ,this valuable suggestion was made by ,sir ,james ,wilson1 who was then ,settlement ,commissioner of the ,punjab1 and1 independently1 by the late ,colonel ,s4 ,l4 ,jacob1 ,r4,e41 who had been a ,chief ,engineer in the ,punjab4 ,the proposals were1 however1 to take off the supply from the ,jhelum lower down than as now arranged in the ,triple ,project4 ,this would have resulted in only a partial utilisation of the ,jhelum water1 in mutilation or heavy alterations to the existing ,lower ,jhelum and ,lower ,chenab ,canals1 in for ever debarring the ,upper ,jhelum and ,upper ,chenab tracts from irrigation1 and in a very costly scheme for the ,lower ,bari ,doab ,canal4#dd #dd ,colonel ,jacob made his suggestion when in ,england after retiring from ,india1 and when he had no levels to guide him4 ,the ,triple ,project as prepared by ,sir ,john ,benton1 ,k4,c4,i4,e41 recently ,inspector ,general of ,irrigation in ,india1 gets over all the above objections4 ,the ,upper ,jhelum ,canal is to irrigate the country which it traverses1 and in the winter1 when the supply in the rivers is restricted1 it is to deliver into the river ,chenab1 above the weir at the head of the ,lower ,chenab ,canal1 a discharge equal to that drawn out higher up by the ,upper ,chenab ,canal4#de ,thus the ,lower ,chenab ,canal1 which at present draws off the whole of the water of the ,chenab in winter1 will not be injuriously affected in any way4 ,the ,upper ,chenab ,canal after irrigating its own tract is to deliver a large volume of water into the ,ravi4 ,the water will be taken across that river by a level crossing1 and supply the ,lower ,bari ,doab ,canal4 ,the water brought into the ,sutlej from the ,beas will remain available for irrigation on the left bank of the ,sutlej1 or possibly for the dry tract ,south of the ,sirhind ,canal area4 ,this fine scheme presented many difficulties and is necessarily costly4 ,the water has to be conveyed a great distance1 and there will be much loss by absorption4 ,the ,ravi crossing will be a very heavy work4 ,the ,upper ,jhelum ,canal has to be taken by a circuitous course round a range of hills1 and to cross numerous heavy torrents4 ,the scheme will1 however1 prove remunerative in spite of immense difficulties as to labour1 caused by the outbreak of plague in the ,punjab a few years ago4 #de ,the ,indus is at a higher level than the ,jhelum4 ,the latter river runs in a comparatively deep valley1 and it is unfortunately impossible to convey the water of the ,indus across this valley4 #b4 ,areas and ,discharges4 ,the figures on which the discharges in the ,triple ,project are based form a useful and interesting object lesson4 ,in order to obtain sufficient water in the winter1 it is necessary to reduce the rabi supply to the existing ,lower ,jhelum ,canal4 ,the figure above given for the ,jhelum indicates the supply available after the reduction4 ,more water will be supplied to the ,lower ,jhelum ,canal for the kharif1 the canal being enlarged for this purpose1 and its total irrigation will be unaffected4 ,the proportion of the culturable commanded area to be irrigated in the new tracts is #ge per cent41 but from this the area irrigated by wells in the ,upper ,jhelum and ,upper ,chenab tracts is deducted4 ,on the ,lower ,bari ,doab ,canal there is little well ,irrigation1 but there are some low-lying tracts near the rivers1 and of these only #ej per cent4 will be irrigated4 ,the kharif and rabi areas are in all cases to be equal4 ,the areas to be irrigated in each crop are as below-- ,lower ,jhelum ,canal #chc1jia acres ,upper ,jhelum ,canal #agb1dhj ,upper ,chenab ,canal #cbd1ahd ,lower ,bari ,doab ,canal #dda1bfd --------- ,total #a1cba1jai ,the total1 excluding the existing ,lower ,jhelum ,canal1 is #icg1ibh acres4 ,with an equal area in the other crop1 the new annual irrigation amounts to #a1hge1hef acres4 ,the kharif duty is taken as #ajj acres at the distributary heads1 this being about the figure actually obtained on the ,lower ,chenab and ,upper ,bari ,doab ,canals1 and the required kharif discharges at the distributary heads are3 ,lower ,jhelum #c1hba c4 feet per second ,upper #a1gbe ,chenab #c1bdb ,lower ,bari ,doab #d1dac ----- ,total1 excluding ,lower ,jhelum #i1chj ,the losses of water in canal and branches have been found to be1 on the ,upper ,bari ,doab ,canal #aj c4 feet per second1 and on the ,lower ,chenab ,canal #h c4 feet per second1 per million square feet of wetted area respectively4 ,the conditions of the latter canal most resemble those on the new canals under consideration4 ,the losses calculated on the wetted areas of the channels1 as designed1 at #h c4 feet per second per million square feet1 are as follows1 in c4 feet per second3 ,lower ,jhelum ,canal #fbd #a1bhh ,upper ,jhelum ,canal #ffd ,upper ,chenab ,canal #a1afa #b1abf ,lower ,bari ,doab ,canal #ife ----- ,total #c1dad ,but in dry years the canals will be worked in rotation during the rabi1 the ,upper ,chenab and ,lower ,bari ,doab ,canals being worked together1 and the ,upper ,jhelum and ,lower ,jhelum together4 ,when the ,lower ,jhelum ,canal is closed1 in course of rotation1 the ,upper ,jhelum ,canal will still be flowing1 and the loss in it1 #ffd c4 feet per second1 has to be added to the figure 7#b1abf7 given above1 thus bringing up the loss to #b1gij c4 feet per second4 ,in order to ascertain what the state of affairs will be in the rabi1 the statistics obtained on the ,lower ,chenab ,canal were examined4 ,these show that the rabi duty at the distributary heads on that canal is #bjf acres4 ,on the ,upper ,bari ,doab ,canal the duty at the distributary heads is #bfc acres1 but #aa per cent4 of the area receives only 8first waterings40 ,the duty based on the remaining area is #bcd acres4 ,but the above duties are only attained by running higher supplies in ,october and ,march than during the intervening four months of the crop4 ,the following remarks and figures are taken from the ,report on the ,project ,estimates3-- 8,the statistics of working of distributaries of the ,chenab and ,bari ,doab ,canals give the average discharges shown in the following table for the three years ending with #aijc-jd4 ,the losses by absorption are calculated on the wetted areas for the different rotational periods4 ,the average discharge less absorption is the supply which reached the heads of the distributaries4 ,,chenab ,,canal4 ---------------------------------------- ---------------------------- ,,period4 ,,aver- -------------------------------------- ,,age4 ,,particulars4 ,octo- ,octo- ,no- ,de-,janu- ,feb-,march4 ber ber vem- cem-ary4 ru- #ast- #afth- ber ber ary #aeth #cast ---------------------------------------- ---------------------- ,cu- ,cu- ,cu- ,cu- ,cu- ,cu- ,cu- ,cu- secs4 secs4secs4secs4secs4secs4 secs4 secs4 ,average supply entering head of canal #aj1aifaj1bheg1ghhe1eice1abge1ejj #f1fjc #f1hji ,deduct absorption #a1fcc #a1fcca1beja1jeca1jcba1aga #a1dcc #a1bfb ---------------------------------------- ---- ,supply at distrib- utary heads for #a1aee1fhe acres1 the average ,bari area #h1efc #h1febf1echd1eajd1jied1cbi #e1agj #e1edf ---------------------------------------- ---- ,proportional supply for #a1afd1eie acres #h1fca #h1gbaf1eijd1egfd1abhd1cfd #e1baa #e1eia ,add absorption for new projects #c1dad #c1dadb1acib1acib1acib1aci #c1dad #b1efd ---------------------------------------- ---- ,supply required for new projects at heads of canals#ab1jdeab1jceh1gbif1gaef1bfgf1ejc #h1fbe #h1aee ---------------------------------------- ---------------------- 8,the average discharge given by the third line is #e1edf1 and the average area being #a1aee1fhe acres1 the duty at the heads of distributaries was #bjh4 8,the area #a1afd1eie is the perennial rabi irrigation of the new projects1 the area #aef1dbd acres1 receiving only first waterings1 being omitted to admit of a fair comparison1 and is only #a per cent4 under the average attained on the ,chenab ,canal in the three years for which the table is prepared4 8,the absorption added for the two first periods is on the supposition that all the canals are open throughout ,october and ,march1 tatilling#df with an average absorption loss of #b1aci cusecs#dg being in force during the other four months4 ,the last line of the table shows the average ,rabi discharge required by the new projects at the heads of canals1 inclusive of all losses calculated on the ,chenab ,canal basis of a duty of #bjh acres per cusec obtained at the heads of distributaries4 #df 8,ttl0 is the ,indian word for rotational closure4 #dg 8,cusec0 is used in ,india for c4 ft4 per second4 8,the ,bari ,doab ,canal statistics furnish the means of the adequacy of available supply being gauged4 ,the following table furnishes particulars for the average supply of water entering the head of the canal for the five years #ahih-ii1 #ahii-aijj1 #aija-jb1 #aijb-jc1 #aijc-jd4 ,the figures for the year #aijj-ja are omitted1 as it was a very abnormal one of very plenteous supply and heavy rainfall3-- 8,the average irrigation for the five years in question was #ddb1cjb inclusive of #aa per cent4 which only receives first waterings4 ,this divided by the average supply1 #a1fhe1 entering the head of a canal gives a duty of #bfc acres per cusec at the heads of distributaries4 ,,bari ,,doab ,,canal4 ---------------------------------------- ---------------------------- ,,period4 ,,aver- -------------------------------------- ,,age4 ,,particulars4 ,octo- ,octo- ,no- ,de-,janu- ,feb-,march4 ber ber vem- cem-ary4 ru- #ast- #afth- ber ber ary #aeth #cast ---------------------------------------- ---------------------- ,cu- ,cu- ,cu- ,cu- ,cu- ,cu- ,cu- ,cu- secs4 secs4secs4secs4secs4secs4 secs4 secs4 ,average supply entering head of canal #c1gfi #b1hifb1agja1geea1fbba1iaf #b1iji #b1bhd ,deduct absorption #eii #eii #eii #eii #eii #eii #eii #eii ---------------------------------------- ---------------------- ,supply at heads of distributaries 7a7 #c1agj #b1biga1egaa1aefa1jbca1cag #b1caj #a1fhe ---------------------------------------- ---------------------- ,corresponding supply for new schemes #c figures line 7a7 #i1eaj #f1hiad1gacc1dfhc1jfic1iea #f1icj #e1jee ,add absorption for new projects #c1dad #c1dadb1acib1acib1acib1aci #c1dad #b1efd ---------------------------------------- ---------------------- ,supply required for new projects at heads of canals#ab1ibdaj1cjef1hebe1fjge1bjhf1jija j1cdd #g1fai ---------------------------------------- ---------------------- 8,the rabi irrigation of the new projects is #a1cba1jai acres1#dh and this divided by #ddb1cjb gives approximately the multiplier #c referred to at 7a7 in the above table4 #dh ,including the ,lower ,jhelum4 8,the figures given in the above table and in the foregoing remarks relate to the aggregate of the areas in the rabi which receives a perennial supply and which only receives first and last waterings4 ,on the ,upper ,bari ,doab ,canal the rabi which receives perennial irrigation is averagely #cic1fdi acres2 the average supply of #a1fhe cusecs gives on this area a duty of #bcd acres per cusec at the heads of the distributaries4 8,in the case of the three projects the aggregate rabi area receiving perennial irrigation as shown by the table1 paragraph #badi supra1 is #a1afd1eie acres3 this is #bif times #cic1fdi2 so that the proportional supply required on this basis would be slightly less than that given by the multiplier #c in the above table4 #di ,not printed4 ,the area is the total rabi area less the area which is to receive only first waterings4 ,in explanation of the difference of the duties3-- ,lower ,chenab ,canal #bjh acres per cusec1 ,upper ,bari ,doab ,canal #bcd ditto1 it may be stated that the ,lower ,chenab ,canal is a comparatively new work1 and that the duty has been steadily rising and1 with the perfect watercourse system1 may be relied on to reach the ,upper ,bari ,doab ,canal #bcd acres per cusec in the course of time for water arriving at the heads of distributaries4 99 99 99 99 99 8#bg4 ,summary of conclusions as to sufficiency of supply4--,the following table shows all the foregoing results in a form readily admitting of comparison3-- ---------------------------------------- ---------------------------- ,,partic- ,,period4 ,,ulars4 ---------------------------------------- ------------ #ast to #fth to ,novem- ,de- ,janu- ,febru- ,march4 #aeth #cast ber4 cem- ary4 ary4 ,october4,october4 ber4 ---------------------------------------- ---------------------- ,cusecs4 ,cusecs4,cusecs4 ,cu- ,cu- ,cusecs4 ,cusecs4 secs4 secs4 ,,average ,,supplies ,,available4 ,very fa- vourable #ba1djj #ae1aej #aa1hejh1fbfaa1bjj #ac1ajj #ba1bej years #a 7#ac4jfc77ac1jfc7 7#ac1jfc77ac1jfc7 in #d ,ordinary #ac1ijj #aa1hej #aj1jjjg1djj #g1fjj #i1ajj #af1ejj years #b #ac1jfc #ac1jfc in #d ,dry years #aj1aej #i1ajj #g1bge #e1iej #e1faj #f1ajj #aa1cde #a in #d ,minimum of #i1gaj #h1jjc #f1fbd #e1haj #e1efc #e1afc #i1gia #ad years ---------------------------------------- ------------ ,require- ments on average of ,lower #ab1jde #ab1ace #h1gbi #f1gae #f1bfg #f1ejc #h1fbe ,chenab ,canal for #c years ,require- ments on average of ,upper ,bari #ab1ibd #aj1cje #f1heb #e1fjg #e1bjh #f1jij #aj1cdd ,doab ,canal for #e years ---------------------------------------- ---------------------- ---------------------------------------- --------------- ,,partic- ,average,deduct ,supply at,duty calcu-,duty calcu- ,,ulars4 supply loss byheads of lated on lated on in absorp-distribu-#a1cba1jai #a1afd1eie river4 tion4 taries4 acres1 the acres1 the gross rabi perennial area4 area4 ---------------------------------------- --------------- ,cusecs4,cusecs4 ,cusecs4 ,,average ,,supplies ,,available4 ,very fa- vourable #aa1haa #c1dad #h1cig #aeh #aci years #a in #d ,ordinary #i1idf #b1ihi #f1ieg #ahi #afg years #b in #d ,dry years #g1fea #b1efd #e1jhg #bei #bbi #a in #d ,minimum of #f1ifh #b1deh #d1eaj #bic #beh #ad years ---------------------------------------- ----- ,require- ments on average of ,lower #h1aee #b1efd #e1eia #bcf #bjh ,chenab ,canal for #c years ,require- ments on average of ,upper ,bari #g1fai #b1efd #e1jee #bfa #bcj ,doab ,canal for #e years ---------------------------------------- --------------- 8,the #ac1jfc shown in brackets represents the parts of the available supply which the canals can carry1 the capacity being as follows3-- ,cusecs4 ,lower ,jhelum ,canal #d1efc ,upper ,jhelum ,canal #h1ejj ------ ,total #ac1jfc ------ 8,the average supplies and duty figures are based on the #ac1jfc cusec maximum capacity and not on the larger available supplies written above these figures where they occur4 8,the above table goes to show the following3 7i7 ,in order to utilize the large supplies available in the ,jhelum ,river in ,october and ,march every year and in some or all of the intervening months in other years1 it is advisable to give the ,upper ,jhelum ,canal the large capacity of #h1ejj cusecs proposed4 7ii7 ,in favourable and ordinary years1 that is1 in #c out of #d1 the available supply will be ample1 as shown by the low duties of #ahi and #afg compared with those obtaining on the ,lower ,chenab and ,upper ,bari ,doab ,canals4 7iii7 ,in dry years1 that is1 #a in #d1 it will be necessary to attain a duty almost exactly the same as that now obtaining on the ,upper ,bari ,doab ,canal4 7iv7 ,that an exceptionally dry year might occur once in #ad years1 when the supply would be #aj per cent4 short of that required by the average ,upper ,bari ,doab ,canal standard of requirements3 such exceptional cases should be met by remissions1 which will be far preferable to wasting the good supplies of #ac years out of #ad4 7v7 ,that the occasional occurrence of dry years makes it inadvisable to attempt a greater proportion of rabi than half of the annual irrigation40 #c4 ,remarks4 ,the ,report on the ,project estimates gives1 for each tract1 remarks on its soil1 rainfall1 height of subsoil water1 circumstances as to existing irrigation from wells or small canals and liability to floods4 ,on a consideration of these matters the decision as to the particular parts of the tracts which are to be irrigated and the areas which are1 in the rabi1 to receive only restricted irrigation1 depends4#ej #ej ,it is not unusual1 in tracts where the level of the subsoil water is high1 say within #ae feet of the surface1 to have some 8kharif distributaries40 ,these are closed in the rabi4 ,this tends to prevent water-logging of the soil4 ,in the rabi the people lift water from wells4 ,there may also be kharif distributaries in dry tracts if there is no water to spare in the rabi4 ,in calculating the sizes of the canals1 ,n in ,kutter's co-efficient was taken at #jbj4 ,in sharp curves the bed is paved on the side next the concave bank4 ,in high embankments where the soil is sandy the best material is used as a core wall4 ,the torrent works on the ,upper ,jhelum ,canal have been mentioned in ,river and ,canal ,engineering1 ,chapter ,,xii4 ,regarding the effect of the new canals on the inundation canals which take off1 lower down1 from the ,chenab below its confluence with the ,jhelum1 it has for long been the policy to gradually shift the heads of these canals upstream in order to obtain better supplies1 or rather to counteract the effect of the abstraction of water for the recently constructed ,lower ,chenab and ,lower ,jhelum ,canals4 ,any such abstraction of water has not much effect on the floods1 but it has much effect in ,april and ,may1 when the rivers have not fully risen1 and in ,september1 when they are falling4 ,in order to estimate the effect on the water level of the ,chenab--below its junction with the ,jhelum--it was necessary to observe discharges of the river1 not only in the winter when it is low1 but in the summer when it is high4 ,the depth of the water was in some places #dj feet1 and the stream #b1jjj feet wide4 ,fortunately the ,subdivisional ,officer was a native of ,india and did not much mind the sun4 ,a discharge curve 7,river and ,canal ,engineering1 ,chapter ,,iii4 ,art4 #e17 having been prepared1 it was possible to construct a diagram with periods of time as the abscissas1 the ordinates representing the average known gauge readings on the different dates and another set of ordinates representing the probable discharges4 ,by deducting the discharges which it was intended that the new perennial canals should draw off1 it was possible to draw fresh ordinates representing the diminished river discharges and the reduced river gauge readings corresponding to them4 ,it was found that the water level would be lowered by about #ac feet in ,april and ,may1 and by about #ae feet in ,september4 ,it was1 however1 shown that by shifting the heads of the inundation canals upstream--the gradients of the canals being flatter than that of the river--the effect of the lowering of the water level could1 as heretofore1 be nullified4 ,,chapter ,v4 ,,proposed ,,improvements ,,in ,,irrigation ,,canals4 #a4 ,preliminary ,remarks4--,the chief improvements which have been under consideration during recent years are three in number4 ,the first is increased economy of water in its actual use in the fields2 the second is reduction of the losses by absorption in the channels2 and the third is distribution by means of modules4 ,regarding the first1 it has long been known that the ordinary methods of laying on the water are more or less wasteful4 ,in ,california1 when the water instead of being applied to the surface of the ground1 is brought in a pipe and delivered below the ground level1 the duty is increased from #bej to #ejj acres4 ,in ,india a field is divided1 by means of small ridges of earth1 into large compartments4 ,the water is let into a compartment and gradually covers it4 ,by the time the further side is soaked the nearer side has received far too much water4 ,frequently the water for a compartment1 instead of being carried up to it by a small watercourse1 is passed through another compartment and this adds to the waste4 ,also the number of waterings given to a crop is often #e or #f1 when #d would suffice4 ,experiments made on the ,upper ,bari ,doab ,canal1 by ,kennedy1 showed that the water used in the fields was nearly double what it might have been4 ,the #ec c4 ft4 shown in ,chapter #a1 ,art4 #d1 as reaching the fields1 were used up when #bh c4 ft4 would have sufficed4 ,it is not certain that the waste is generally quite as much as the above4 ,it is possible that the restricted supplies might have given smaller yields of crops4 ,more recent experiments made by ,kanthack on the same canal give the needless waste as about #be per cent4 ,the field compartments ought1 according to ,kennedy1 to be #gj;ft4 square1 the small branch watercourses being #adj;ft4 apart4 ,it would be better to have still smaller compartments1 but this would be rather hard on the people4 ,at one time ,government issued orders1 in ,northern ,india1 that compartments of #abif square feet were to be used1 and that1 otherwise1 increased water rates would be charged1 but the orders were never enforced4 ,they were thought to press too hardly on the people4 ,extreme measures for enforcing economy in the use of water in any country are likely to be introduced only when they become absolutely necessary owing to the supplies of water being otherwise insufficient4 #b4 ,reduction of ,losses in the ,channels4--,for several years experiments have been going on in the ,punjab as to the effect of lining watercourses with various materials4 ,the following conclusions have been arrived at#ea3-- #ea ,punjab ,irrigation ,paper ,no4 #aa ,c4 8,lining of ,watercourses to reduce absorption losses4 ,experiments of #aijh-aiaa40 ,i4 ,,ordinary ,,unlined ,,trenches4 7a7 ,the rate of absorption varies greatly1 and this is due probably to unequal fissuring of the upper layers of the soil4 7b7 ,the rate of absorption in the three hottest months averaged #jega feet per hour1 or more than double the rate 7#jbf7 in the three coldest months4 ,the difference is ascribed to the greater viscosity of the water when cold4 7c7 ,the average losses with canal water were #jcae feet per hour1 or #hge c4 feet per second per million sq4 feet4#eb ,with well water the figures were #ajif and #cje4 ,the conclusion is that the silt in canal water reduces the losses by more than two-thirds4 #eb ,this loss of #hge c4 ft4 per second was in water only about a foot deep4 ,this confirms the conclusion arrived at in ,chapter ,i1 ,art4 #d1 that the depth of water is not a factor of much importance4 7d7 ,with canal water the average loss decreased by #dj per cent4 7from #jdia to #jbic7 in about four years4 ,this was no doubt due to the effect of the silt4 ,with well water the loss at the end of four years 7#bbic7 was nearly four times as great as at first 7#jeia74 ,this may have been due to removal of the finer particles of soil by the water1 but the experiments were made at only one place1 and were not conclusive4 ,,ii4 ,,lined ,,trenches4 7e7 ,with trenches lined with crude oil inch thick1 or with ,portland cement inch thick1 or with clay puddle #f inches thick1 the 8efficiency ratios10 as compared with unlined trenches1 are respectively about #dj1 #eg and #eg1 the age of the lining being four years4 ,the efficiency ratio is the inverse of the loss4 ,thus with an efficiency ratio of #c the loss in the lined trench is #cc per cent4 of that in the unlined trench4 7f7 ,the efficiency ratio in the case of oil may diminish at the rate of #aj per cent4 per annum1 but in the case of cement and clay puddle it tends to increase rather than to decrease4 ,assuming that the efficiency ratios are only #cj1 #de and #de1 and that the loss in an unlined channel is #h c4 feet per second per million sq4 feet1 the saving in water by using channels lined with oil1 cement and puddle respectively would be #ecc1 #fbe and #fbe c4 feet per second4 ,the average duty of the water at the canal head is about #bdb acres1 and the average revenue per acre is ,rs #cic4 ,the revenue from #a c4 ft4 of water at the canal head is thus ,rs #iej4 ,only about half the water reaches the fields 7,chapter ,i41 ,art4 #d71 and the revenue from #a c4 ft4 of water which reaches the fields is about ,rs #aijj4 ,the mean of the above two sums is ,rs #adbe4 ,if #f c4 ft4 of water per second could be saved the revenue would be increased by ,rs #h1eej per annum4 ,the cost of lining a million square feet of channel with oil1 cement and puddle is estimated at ,rs #cj1jjj1 ,rs #bg1ejj and ,rs #ce1jjj respectively4 ,allowance has to be made for the fact that watercourses flow intermittently1 and that a lined channel gives no saving when it is not in flow1 also that extensions of canals might have to be undertaken in order to utilise the water saved4 ,after making these allowances it is estimated1 in the paper above quoted1 that the saving effected by lining a million square feet with oil1 cement or puddle represents the interest on a capital sum of ,rs #fi1cjj1 ,rs #ha1bej and ,rs #ha1bej respectively1 or #b or #c times the sums sunk in constructing the linings4 ,hitherto the experiments have been carried out on a moderate scale1 but extensive operations are now being undertaken on the ,lower ,chenab ,canal1 and possibly on others4 ,in cases where it is not desired to incur much expenditure1 it may be a good plan to construct watercourses to a cross section somewhat larger than that ultimately desired4 ,the silt deposited on the bed and sides forms1 in most cases1 a more impervious lining than the original soil4 ,the same plan can be adopted in the tail portion of a distributary4 ,in a larger channel there would be less certainty that any deposit would take place unless short lengths1 at frequent intervals1 were excavated to the true or ultimate section1 so as to form weirs and spurs2 and even these might not stand4 ,in ,italy1 in cases where the water naturally contains lime in suspension1 the beds of canals have become gradually watertight by the deposit of lime in the channel4#ec ,in some cases lime has been artificially added4 ,it appears that a considerable period of time is necessary for the process4 #ec ,min4 ,proc4 ,inst4 ,c4 ,e4 ,vol4 ,,cxvi4 #c4 ,modules4--,a module is an appliance which automatically gives a constant discharge through an aperture1 however the water level on either the upstream or downstream side of the aperture may fluctuate4 ,in an old and simple form of module there is a horizontal orifice in which works loosely a tapering rod attached to a float4 ,the water passes through the annular space surrounding the rod4 ,if the water level rises1 the rise of the float brings a thicker part of the rod to the orifice and reduces the annular space4 ,in another kind of module the water is discharged through a syphon4 ,if the water level alters1 the syphon moves in such a way that the head1 or difference between the levels of its two ends1 remains the same4 ,the great objections to modules are that they are liable to get out of order or to be tampered with4 ,a module recently invented and patented by ,gibb#ed has no movable parts1 and is not liable to these objections4 #ed ,for description see ,appendix ,h4 ,a few years ago the question of the desirability of using modules for the outlets of distributaries in ,india was raised4 ,the opinions of a large number of the senior canal engineers were called for and considered1 and since then the subject has been thoroughly discussed4 ,there are certain inherent difficulties in the way of moduling the outlets of a distributary4 ,owing1 for instance1 to rain further up the canal1 or to the closure of a distributary owing to a breach in it1 the canal supply may increase1 and it may be necessary to let more water into the distributary under consideration4 ,under the present system any excesses of water are automatically taken by the outlets4 ,if all outlets were rigidly moduled they would discharge no more than before the excess supply came in1 and the excess supply would all go to the tail of the distributary1 and1 most likely1 breach the banks4 ,to get over this difficulty1 the module has to be so arranged that when the water level in the distributary rises to a certain 8maximum limit0 the module ceases to act as such1 and the discharge drawn off from the distributary increases as the water level rises4 ,again1 the discharge of the distributary may at times be considerably less than its full supply4 ,in order that1 in such a case1 the outlets towards the tail of the distributary may not be wholly deprived of water1 it has to be arranged so that when the water level in the distributary falls below a certain 8minimum limit0 the modules cease to act as such1 and draw off supplies which are less the lower the water level4 ,such supplies are not in proportion to the full supplies of the outlets4 ,it will1 however1 be shown presently that low supplies need seldom be run4 ,when a distributary1 say the upper reach1 contains silt1 the water level corresponding to a given discharge is higher than before1 and care has to be taken that the maximum limit is high enough4 ,at the same time the minimum limit must be so low that it will not be passed when the silt scours out4 ,the difference between the maximum and minimum limits is called the 8range0 of the module4 ,in ,gibb's module the above conditions can be complied with4 ,the module is placed outside the bank of the distributary4 ,the water is drawn off from the distributary by a pipe1 whose lower edge is at the bed level of the distributary1 and delivered from the module into the watercourse through a rectangular aperture at a higher level than that of the pipe4 ,it is possible that1 owing to the high level of the aperture1 some rolling silt which would otherwise have passed out of the distributary may remain in it4 ,the height of the aperture also prevents the watercourse from drawing off any water at all when the water level of the distributary falls below a certain level1 but this objection is not important4 ,an escape weir or notch is provided so that when the water level in the distributary rises to the maximum limit some water overflows into the watercourse4 ,on the whole it appears that all difficulties can be got over1 though a good deal of care and precision is necessary in fixing the exact height of the maximum and minimum limits4 ,the difficulties under consideration will all be reduced if some of the outlets on a distributary are left unmoduled1 and this is desirable on other grounds4 ,when the supply is normal1 i4e4 between the maximum and minimum limits1 and all modules are working1 the supply entering the distributary must be regulated with great precision4 ,the outlets draw off a certain supply4 ,if less than this enters the distributary the tail outlets must go short4 ,if more enters there will be a surplus at the tail1 though it can probably be disposed of1 because the tail water will rise above the maximum limit4 ,for short periods1 say an hour or two1 no trouble arises because the distributary acts as a reservoir1 the water level rising to take in any excess supply1 and falling to allow for a deficiency4 ,at the tail the rise and fall may be hardly perceptible4 ,but if the supply were deficient for a whole night the tail outlets would certainly go short4 ,this could theoretically be remedied to some extent by letting in an excess supply for a short time and causing the water level at the tail to rise above the maximum limit1 but in practice no such system of compensation could be worked4 ,the very fact of the tail outlets having gone short for a night would not be known4 ,the proper method of preventing any such troubles as those under consideration is to leave some of the outlets on the distributary un-moduled4 ,it has been more than once mentioned that there are periods when a distributary is run1 not full1 but about three-fourths full4 ,if that were done in the case of a distributary whose outlets were mostly moduled1 the water level would probably be below the minimum limit1 and the modules would not be acting as such4 ,the outlets would not1 under these circumstances1 obtain their proper proportionate supplies4 ,this difficulty can1 no doubt1 be got over by running the distributary full for short periods at a time instead of three-fourths full for longer periods4 ,the people1 when once they understood the case1 could arrange to use the water in greater volume for two days instead of in smaller volume for three4 ,if this arrangement comes into force it will not be necessary to design distributaries--see ,chapter ,,iii1 ,art4 #d--so as to have a good command when three-fourths full supply is run4 ,on nearly every distributary there are some watercourses whose command is bad1 and it has been stated 7,chapter ,,ii1 ,art4 #i7 that in an ordinary unmoduled distributary the sizes of the outlets in such cases should be extremely liberal4 ,to module any such outlet would cause a lowering of the water level in the watercourse and would interfere with the irrigation4 ,such outlets should not be moduled4 ,again1 there are some few outlets which are not submerged1 i4e41 there is a free fall into the watercourse4 ,the discharge does not depend on the water level in the watercourse1 and it is not affected by any enlargement or clearance of it4 ,it depends only on the water level in the distributary4 ,this water level1 if most of the outlets are moduled1 will be fairly constant4 ,such outlets need not be moduled1 and they should not be moduled unless the other unmoduled outlets in the reach concerned are sufficiently numerous1 and perhaps not even then1 because moduling involves some expense4 ,a distributary generally has some falls which divide it into reaches4 ,immediately upstream of a fall the water level for a given discharge is not affected by the silting or scouring of the channel4 ,any outlets near to and upstream of the fall are less subject than others to variation in discharge1 and are suitable for non-moduling in case a sufficient number of unmoduled outlets is not otherwise obtainable4 ,regarding the watercourses at the extreme tail of a distributary it has been pointed out 7,chapter ,,iii41 ,art4 #g7 that in an ordinary case they should not be left without masonry outlets1 because they may then lower the water level and so unfairly reduce the supply of any watercourse1 even though upstream of them1 which has such an outlet4 ,but any outlets near the tail of a distributary can suitably be left unmoduled because of the difficulty of ensuring that the supply at the tail shall be exactly what is needed4 ,gibb's modules have been tried on various distributaries in the ,punjab and found to give good results4 ,it is believed however that in only one case has a whole distributary been moduled4 ,the distributary is a large one1 its length being #ce miles4 ,it appears that the discharge reaching the tail of the distributary is not constant but varies1 as was to be expected1 when the head discharge varies for any length of time4 ,the command on the distributary is good4 ,there is nothing to show that matters would not have been improved1 and money saved1 by leaving some of the outlets without modules4 ,it has been remarked above1 that at the downstream end of a reach ending in a fall1 the ,f4,s4 level of a distributary is not affected by silt4 ,at the upstream end of the reach it is affected4 ,there are thus two gradients1 one flat1 and one steep4 ,it appears to have been decided in one case in the ,punjab1 that the minimum limit of supply for the module should be about half an inch below the flat line and the maximum limit #c feet above the steep line4 ,in many cases a greater range would be required1#ee say a foot4 #ee ,it is understood that a range of a foot can easily be arranged for1 and that ranges of #c or #d feet can be introduced at slightly increased cost4 ,in ,chapter ,,iii4 ,art4 #g1 the case of a distributary without modules but with the outlets carefully adjusted1 was considered4 ,the question to be decided in each case is whether such an arrangement is preferable to moduling some of the outlets4 ,this turns largely on the amount of attention which would be bestowed on the case4 ,in view of the difficulty of securing such attention and of the trouble of constantly making alterations in a certain number of outlets1 it is probable that moduling will in many cases be considered preferable4 ,the question of moduling the heads of distributaries has also been considered in the ,punjab4 ,for minor or small distributaries modules are feasible4 ,for a large distributary a module would be expensive and it appears that the present system of regulating is preferable4 ,kennedy's 8,gauge ,outlet10 which is a kind of semi-module is described in ,appendix ,k4 ,it is being tried in the ,punjab4 ,,appendices4 ,,appendix ,a4 ,,divide ,,wall ,,on ,,lower ,,chenab ,,canal4 7,see page #ej1 first footnote47 ,illustration3 ,,fig4 #bg4 ,the ,gagera branch of the ,lower ,chenab ,canal--the left-hand branch in fig4 #bg--was found to silt4 ,it was proposed to make a divide wall 7fig4 #bg7 extending up to full supply level4 ,the idea is unintelligible4 ,the silt does not travel by itself but is carried or rolled by the water4 ,as long as water entered the ,gagera branch1 silt would go with it4 ,the authorities1 who had apparently accepted the proposal1 altered the estimate when they received it1 and ordered the wall to be made as shown dotted and of only half the height4 ,this was done4 ,the idea seems to have been that the wall would act as a sill and stop rolling silt4 ,this is intelligible1 but such sills do not always have much effect on rolling silt4 ,moreover1 there was a large gap1 ,a ,b1 in the wall4 ,the work is said to have proved useless1 and proposals have been made to continue the wall from ,a to ,b4 ,in this form it is conceivable that it may be of use4 ,,appendix ,b4 ,,specification ,,for ,,maintenance ,,of ,,channels4 7,see page #ach47 ,i4 ,,roads ,,and ,,banks4 #a4 ,filling ,holes4--,holes to be all dug out and thoroughly opened and inspected1 then to be filled in with rammed earth4 ,never to be filled in a hurry or without digging out4 #b4 ,dressing4--,heavy soil to be dressed even4 ,light sandy soil to be disturbed as little as possible1 and grass in such soil not to be removed except when in large tufts4 ,when dressing is done1 the road to be given 7as far as possible7 a transverse slope from the canal side of about #a in #ej4 #c4 ,trees4--,branches to be lopped so as not to obstruct riders4 ,great care is needed to see that the men do not lop needlessly high4 ,roots1 if projecting on road1 to be covered up or cut out4 #d4 ,petty ,repairs4--,settlement or wearing down1 if slight1 should be made good on maintenance estimates1 otherwise on special estimates4 ,cracks should be dug out and filled in and rammed4 ,old 8dead men0 or walls of earth should be utilised or at least levelled down4 #e4 ,sand or 8,reh0 ,soil4--,can be dug out to a depth of #i inches and removed to a distance1 and 7the places having been inspected by the ,subdivisional ,officer7 replaced by good soil got from pits or berms1 the places being selected with care4 ,if the lead is slightly askew1 the stuff removed can be put in the same pits from which earth is got4 #f4 ,laying long coarse ,grass on ,road4--,this can be done in cases where the removal of sand or 8reh0 is not practicable or has proved ineffective4 ,the grass is laid crosswise to prevent wheels sinking in4 ,,ii4 ,,jungle ,,and ,,trees4 #a4 ,jungle4--,to be cut close to the ground or to be dug out by the roots when ordered4 ,to be burned as soon as dry4 ,dead branches1 twigs1 etc41 to be burned or removed to rest-houses1 and not left about on canal land4 ,precautions to be taken against damage by fire to forests1 etc4 ,clearance to include the channel#ef and both roads1 and any jungle on the slopes of the spoil which obstructs the roads4#eg #ef ,jungle on inside slopes not to be cleared where banks fall in or where channel is too wide4 #eg ,when an embankment runs parallel to an inundation canal1 a chain or so distant1 the intervening space need not be cleared1 nor need the top of a bank be cleared if it is so uneven that it is not a road4 #b4 ,trees4--,trees which fall into a channel or across a road to have their branches cut away at once4 ,the trunk to be removed so far as is possible4 ,trees which are dead or broken off should be felled1 also those which have been blown into inclined positions1 unless bad gaps will be caused4 ,trees 7unless required for stock7 to be sold as they lie and removed1 including the parts below ground1 by purchasers1 within a fixed time4 ,logs1 etc41 not to be left lying about on canal land4 ,stumps1 etc41 to be made into charcoal and the holes filled up4 ,note4--,the above works 7,parts ,i4 and ,,ii47 to be done immediately after the rains 7repairs to roads and removal of trees1 branches1 etc41 being also done during the rains or whenever necessary7 and finished at latest by #cast ,october4 ,,iii4 ,,cattle ,,crossings ,,or ,,gh,,ts4 #a4 ,repairs4--,ghts to be dressed1 strengthened1 and kept neat1 the bank being thrown back and curved so as to give a long inner slope1 and lumps1 etc41 levelled off4 #b4 ,closures4--,to be closed 7by order of ,subdivisional ,officer and no one of lower rank7 only when very near to a bridge or near to another ght4#eh ,if closed1 to be staked up and bushing to be added4 ,not to be closed by loose thorny branches4 ,not to be allowed close to any milestone1 outlet1 etc4 #eh ,regarding ghts at bridges1 see ,chap4 ,,ii41 ,art4 #ab4 #c4 ,small ,ghts4--,ghts where only foot-passengers cross1 can run diagonally up the slopes or as may be convenient4 ,they should be dressed and kept in order4 #d4 ,canal ,road at ,ghts4--,at all ghts care must be taken that the canal road1 especially if used for driving1 is not cut up and is kept in proper order4 ,,iv4 ,,miscellaneous ,,items4 #a4 ,rubbish or ,obstructions in ,bed of ,channel4--,to be removed from the channel when it is laid dry1 and not left till it is about to be reopened4#ei ,old stakes1 etc41 to be sawn off when crooked or too high4 #ei ,where the bed is too low1 no rubbish clearance should be done except in the case of very large snags1 etc4 #b4 ,temporary ,aqueducts or ,damaged ,wooden ,bridges4#fj--,to be removed before water is expected 7but not sooner than is necessary7 and the banks repaired and made good4 #fj ,this applies to inundation canals4 ,,appendix ,c4 ,,specification ,,for ,,maintenance ,,of ,,masonry ,,works4 7,see page #ach47 #a4 ,general ,repairs4--,masonry1 plaster1 pitching1 etc41 to be kept in repair4 ,pitching1 where defective or out of line1 to be made right4 ,bumping posts to be fixed in proper positions4 ,earth to be added to ramps1 etc41 where needed4 ,metalling to be regularly seen to4 ,needles1 planks1 hooks1 railings1 winches1 lamp-posts1 lamps1 etc41 to be kept in order and complete4 ,bricks1 bats1 etc41 to be properly stacked4 ,needles1 etc41 to be neatly stacked on rests or with bricks under them4 ,all surplus and useless needles1 etc41 to be removed4 ,huts to be kept in repair4 ,extra mud walls or screens not to be allowed when unsightly4 ,all verandah openings to be edged with a #f-;inch band of whitewash4 #b4 ,jungle4--,all masonry to be kept free from jungle growth1 and all piers free from caught jungle4 ,for this purpose long bamboo weed-hooks to be supplied4 #c4 ,dressing1 etc4--,rubbish1 lumps of earth1 logs1 etc41 to be cleared away1 pits and holes filled up4 ,banks1 slopes1 etc41 of main and branch channels in the neighbourhood of the work to be specially levelled and dressed4 ,note4--,all works should be specially seen to in ,october1 and everything be in order by #cast ,october4 ,,appendix ,d4 ,,watching ,,and ,,protecting ,,banks ,,and ,,embankments4#fa 7,see page #ach47 #fa ,this is reprinted from ,punjab ,rivers and ,works4 ,it was drawn up for inundation canals and flood embankments4 #a4 ,watching4--,every watchman employed to have a fixed headquarters and a fixed beat4 ,if there is no permanent hut on or near the bank1 grass huts should be erected by the men at the places fixed4 ,the presence or absence of the men to be frequently tested by the mate and suboverseer4 ,the suboverseers tests to be recorded in a book and to form the subject of frequent inquiry by the ,subdivisional ,officer1 who will also record his remarks and take proper action in case the suboverseer is in fault4 #b4 ,gauge ,readers1 ,regulating ,establishment1 ,bungalow ,watchmen1 etc4--,to be made to assist whenever possible4 ,the allotment of a beat to each such man has been separately ordered4 #c4 ,employment of ,men on ,repairs4--,the men1 when not otherwise occupied1 to do petty repairs1 etc41 within their beats1 but not to be put on miscellaneous duties and sent about as messengers1 nor to act as orderlies or khalassies4 #d4 ,strength of ,establishment4--,should generally be greater for one and a half months in ,july and ,august than at other times4 ,care to be taken as to this and as to dismissing men when no longer needed4 #e4 ,stakes and ,mallets4--,to be collected beforehand1 if necessary1 at suitable places1 to be accounted for at end of flow season and balance taken care of4 #f4 ,breaches4--,the ,establishment to be trained by the ,subdivisional ,officer to report every breach to all officials with the greatest possible speed4 ,the mate1 daroga1 and suboverseer to remain there till the breach is closed and to promptly send a report on the prescribed form to the ,subdivisional ,officer4 #g4 ,serious ,breaches4--,in case of serious breaches of main channels the ,subdivisional ,officer to himself reach the spot as soon as possible4 #h4 ,breach ,reports4--,see printed form ,m#fb attached4 ,to be promptly submitted for each breach to the ,executive ,engineer4 ,the report contains a column for cost of closure4 ,this means the stoppage of the flow and not the complete making up of the banks4 ,the column for remarks of the ,executive ,engineer should be filled in and the report promptly returned to the ,subdivisional ,officer1 who will1 in the meantime1 be making up the banks and preparing a requisition or estimate4 #fb ,not printed4 #i4 ,progress ,report4--,with the ,executive ,engineer's monthly progress report a list of breaches will be submitted1 canal by canal1 with columns showing date of occurrence and cost of closure4 ,the return should be on the attached form ,g4#fc ,the ,subdivisional ,officer should also submit this form to the ,executive ,engineer4 #fc ,not printed4 ,the form differs slightly from a form prescribed by the ,chief ,engineer for general use in the ,province4 #aj4 ,estimates4--,the cost of breaches is not to be charged to maintenance estimates4 ,at the close of each month the ,executive ,engineer should submit or sanction an estimate1 accompanied by the breach reports1 for closing any breaches which have occurred and making up the banks4 #aa4 ,breaches in the ,flooded ,area near ,canal ,heads4--,these may be of special importance4 ,it may be impossible to do any good and money may be uselessly spent4 ,in any such cases the ,subdivisional ,officer should at once proceed to the spot and the case should be reported by wire to the ,executive ,engineer and1 if necessary1 to the ,superintending ,engineer4 #ab4 ,breaches in ,flood ,embankments4--,the ,subdivisional ,officer must at once proceed to the spot and the case be reported by wire to the ,executive ,engineer and ,superintending ,engineer4 ,the ,breach ,report forms can be submitted partially filled in at the earliest possible moment and a complete form afterwards4 ,,appendix ,e4 ,,specification ,,for ,,bushing4 7,see page #aci47 #a4 ,the object of bushing is to form a silt berm and thus prevent or stop the falling in of the banks4 #b4 ,the branches must be thickly packed in order that the water among them may become still1 and also in order that they may not be shifted by the stream4 ,if thickly packed1 the pegs required will also be fewer4 ,most of the branches should be leafy and freshly cut1 but1 mixed with these1 there may be a proportion of kikar or other leafless branches4 ,frequently it is possible to utilise jungle trees of small value1 bushes1 scrub jungle1 or even long grass4 #c4 ,except when the bushes are to be very small or the length to be bushed very short1 the proposed line for the edge of the berm should be marked out by long stakes driven in the water at fairly close intervals4 ,otherwise the work may be badly done and the berm formed imperfect and out of line4 #d4 ,as the berm formed is not likely in any case to be perfectly straight1 and as subsequent additions to it will be difficult1 while trimming it will be easy1 the bushes should extend slightly beyond the line of the proposed berm4 ,care should be taken that the lower branches1 which cannot be seen when once submerged1 are long enough4 #e4 ,the branches should be piled up to above water-level1 so that1 as they settle1 they will assume the position desired1 but to lay them high above full-supply level on the slopes is useless and wasteful4 ,if the pegs have to be driven at a high level1 the branches should be attached to them by thin ropes or twine4 ,long pegs standing up high above the ground are also wasteful4 ,the pegs should as far as possible be kept in line and their heads at one level4 #f4 ,if bushing is begun during low supply1 it need not1 at first1 extend up to full-supply level4 ,more branches1 freshly cut1 can be added as the supply rises4 ,in any case it is generally necessary to make some additions to bushing from time to time1 and this should be explained to contractors and others when fixing the rates4 #g4 ,if the trees from which branches are cut are in desirable places1 the branches should be cut with judgment2 but where trees are in places where they should not be 7e4g41 on the inside slopes of the channels71 all the branches may be cut off4 ,the trunk may be left temporarily in order to supply more branches4 ,,appendix ,f4 ,,escapes4 7,see page #i47 ,there are no definite rules regarding the capacity of the escapes to be provided on a canal4 ,on some canals in dry tracts of country the discharging power of the escapes is a mere fraction of that of the canal4 ,in other cases it is about half that of the canal4 ,in a district liable to heavy rain an escape1 say at a point where a canal divides into branches1 should be able to discharge about half of the main canal supply4 ,on branches1 escapes1 if provided at all1 usually discharge into reservoirs1 and their period of working is very limited3 it may be only twenty-four hours4 ,on distributaries1 escapes are seldom provided4 ,it has been suggested1 in connection with modules1 that the people irrigating from each watercourse should be responsible for disposing1 by means of it1 of a certain quantity of surplus water4 ,this would be too rigid a rule4 ,on some watercourses there is much waste land or land under rice cultivation2 in such cases surplus water can be passed off without damage4 ,the canal subordinates are fully cognisant of such cases1 and they arrange accordingly4 ,in other cases surplus water would do some damage2 but on nearly every distributary the full supply1 even when there is no demand for water1 can be got rid of for a few hours1 or even more1 without a breach occurring4 ,escapes at outlets1 in connection with modules1 can be arranged by means of waste weirs or by means of ,gregotti's syphons 7sifoni autolivelatori74 ,the following is an abridged translation of part of a pamphlet by ,gregotti3-- ,the figure represents one of the syphons installed in the 8,centrali ,milani40 ,a is the supply basin of the 8,centrali10 which ends in the syphon ,b4 ,the latter is constructed with mouthpiece of rectangular section a1 which is submerged in the basin ,a4 ,a weir divides the mouthpiece of the syphon from the descending branch1 c1 of the same1 also rectangular in section4 ,the weir crest is at level dd1 from #b to #g cm4 below the maximum level of water surface which it is desired not to exceed in the supply basin4 ,illustration3 ,,fig4 #bh4 ,the descending branch1 c1 has at its base a small tank e1 which forms a water seal4 ,the syphon is completed by a tube f1 which is attached to the intake branch of the syphon and which ends at a level of #b to #g cm4 above the previously mentioned surface dd4 ,as soon as the water surface in the supply basin tends to rise above the plane dd1 a filament of water1 in falling over the weir b1 pours down the descending branch c1 and when the water has risen from #b to #g cm4 above the crest of the weir1 the thickness of the falling stream has become such that it is able1 by lapping1 with a wave-like course1 the wall gg1 to extract the air that has become enclosed in the syphon1 and which cannot be replaced because the space in which the stream acts is closed at its base by the water in the tank e2 and at the top also the aeration tube is closed by the rise in the water surface of the supply basin4 ,from this point the syphon action quickly becomes fully established and begins to give its full discharge4 ,the discharge that is given is equal to that of an orifice in a thin partition if certain limitations are allowed for between the fall used in the syphon and the height of the arch1 that is1 the distance from the crest of the weir to the inside roof of the syphon4 ,the discharge is given by the formula ,q ,a7#b;g h74 ,q discharge of syphon in cubic metres per sec4 a coefficient of reduction of discharge which varies between wide limits4 ,a the minimum cross-sectional area of the syphon in square metres4 g value of acceleration due to gravity4 h the fall1 or the difference of level in metres between the water surfaces in the supply basin ,a and in the small tank e4 ,as soon as the supply basin surface falls1 the opening of the aeration tube becomes uncovered and air is drawn into the syphon4 ,but until the surface has fallen some centimetres the supply of air is not sufficient to cause the syphon action to stop completely1 and thus the escape varies gradually from the maximum discharge to zero as the water surface falls a few centimetres till it reaches its original level4 ,in certain cases it is possible to do without the aeration tube1 especially when the fall used in the syphon is not great and when it is possible to arrange matters so that the velocity of the water flowing past in front of the syphon is small4 ,the syphon with a width of #c metres escapes #h cubic metres per sec4 of water4 ,,appendix ,g4 ,,gauges4 7,see ,chap4 ,,iii41 ,arts4 #b and #c2 also see ,hydraulics1 ,chap4 ,,viii41 ,art4 #e1 and ,appendix ,h47 #a4 ,the gauge should be placed on that bank and facing in that direction which enables it to be most conveniently read by the gauge reader and by officials passing the place4 #b4 ,the gauge should be of enamelled iron secured by copper screws to a post of squared and seasoned wood which is either driven beforehand#fd into the channel or spiked to a masonry work4 ,even in the deepest channel a long enough post can be arranged for4 ,a masonry pillar is not necessary4 ,the post may be rectangular in cross-section1 with upstream and downstream edges cut sharp4 ,this prevents1 or greatly reduces1 the heaping up of water at the upstream side and the formation of a hollow downstream4 ,if the 8,ward0 gauge of two vertical planks is used1 the planks should meet at an acute angle1 not a right angle1 and not be wider than #g inches each4 #fd ,driving after the gauge is attached may loosen or break the screws4 #c4 ,the top of the gauge should be slightly above the highest probable water-level4 ,the post should extend up to the top of the gauge4 #d4 ,if ever the graded bed of the channel is altered the zero of the gauge should be altered4 ,there may be some risk of confusion at first1 but it can be avoided by exercising due care and making notes4 ,the levels of the old and new zeros should be recorded4 #e4 ,a gauge at a distance from the bank is objectionable4 ,it collects jungle1 cannot be properly read1 and is liable to be damaged by floating logs or boats4 ,a gauge should be as near as possible to one bank or the other4 ,if the bank is vertical1 the gauge should be quite close to it4 ,if1 owing to silt deposit1 the gauge is dry at low supply1 the deposit can be removed by the gauge reader4 #f4 ,every regulator should be given a name1 generally that of a neighbouring village and not that of a channel1 and the gauge book headings should be drawn up in an intelligent and systematic manner4 ,each main channel should be entered in order1 and each regulator on the channel--together with the head gauges of all channels which take off there--should be entered1 commencing from upstream4 ,a specimen is given on page #aji4 ,thus the head gauge of any branch appears in the register of the main channel from which it takes off1 other gauges on the branch appearing in the register for the branch4 ,and similarly as regards a distributary which has gauges other than the head gauge4 #g4 ,each gauge reader should be supplied with a register1 each page having1 besides the counterfoil1 as many detachable slips--marked off by perforations--as there are officials--usually the ,subdivisional ,officer1 zilladar and suboverseer--to whom daily gauge reports are to be sent4 ,the titles and addresses of these officials are printed on the backs of the respective slips4 ,the slips and counterfoil have printed on them a form--similar to part of the specimen shown on page #aji--showing the names of all the gauges read by that particular gauge reader1 so that he has merely to fill in the date and readings1 tear off the slips and despatch them4 ,the posting of the register in the subdivision is facilitated if each gauge has a number and if the corresponding numbers are printed--besides the names--on the gauge slips4 ,if the gauge reader does not know ,english1 the headings of the slips are printed in the vernacular4 ,if the gauge readings are telegraphed1 there may be only one slip--besides the counterfoil--which is sent to the telegraph signaller4 ,,appendix ,h4 ,,gibb',s ,,module4#fe 7,see p4 #afd47 #fe ,this description has been supplied by ,glenfield ,kennedy1 ,kilmarnock4 ,the modules can1 it is understood1 be obtained from them4 ,the attributes of a perfect module are many and varied1 but in ,gibb's module they have all been successfully embodied in what is probably the simplest piece of apparatus of its kind ever devised4 ,the following summary of the characteristics of ,gibb's module is1 therefore1 equivalent to an enumeration of the attributes of a perfect module3-- ,gibb's module ,cannot be tampered with1 ,cannot get out of order1 since it has no moving ,silt or other solid matter in the water parts1 and because of its cannot affect its action1 extreme simplicity4 ,requires no attention1 ,it is accurate1 being designed on scientific ,works with very small loss of head1 hydraulic principles4 ,it is portable1 and can be erected at any desired site very simply and easily4 ,it is strong and durable4 ,the range of variation of both up- and downstream water-levels through which the discharge remains constant is more than sufficient to meet all the requirements of irrigation canals4 ,the sufficiency of the delivery can be ascertained at a glance4 ,the water can be drawn from any desired depth in the parent channel4 ,when desired1 means are provided whereby the supply can be closed or opened at will4 ,means are provided1 if desired1 for a sudden increase of discharge when the upstream water-level exceeds a certain limit1 so that surplus water1 which might endanger the safety of the canal1 is allowed to escape into the branch whenever the danger limit is reached4 ,the upstream water-level at which escapement begins can be fixed in accordance with the requirements of each site1 and the action of the escape notch is independent of the opening and closing of the module4 ,no designing or calculations are required4 ,these have already been worked out4 ,known the discharge required1 the module is supplied complete and ready for setting in position in the canal bank4 ,,hydraulic ,,principle4 ,the entire absence of moving parts is the chief feature of ,gibb's module2 the water simply regulates itself by using up all the excess of energy over and above that required to discharge the correct supply of water4 ,the way in which this takes place will be understood from the following analogy3-- ,we all know that when we stir tea in a cup so as to make it spin1 the liquid rises at the rim of the cup and curves down into a depression in the middle1 and the greater the spin the more marked this effect is4 ,it is1 we know1 the centrifugal force produced by the spin that makes the tea remain high at the rim of the cup4 ,if1 while the tea is thus spinning1 a teaspoon is held so that it dips slightly below the surface of the liquid near the rim1 it will obstruct the flow of the outer portion of the liquid1 which will fall in towards the depression in the middle4 ,the reason for this1 of course1 is that the centrifugal force is absorbed when we interrupt any part of the spin with the teaspoon2 hence the liquid must fall1 and we know that when liquid falls it uses up 8head0 or energy4 ,in ,gibb's module a similar action is made to take place in a steel chamber1 semicircular or spiral in plan1 through which the water flows in a semicircular path instead of circulating round and round as in the teacup4 ,the surface of the stream1 however1 assumes the same form as it does in a cup1 because it flows under the same conditions4 ,across the chamber are fixed a number of vertical steel diaphragm plates which take the place of the teaspoon in the above analogy4 ,the lower edges of these plates are of such a shape1 and they are fixed at such a height from the bottom of the chamber1 as to allow a stream of just the correct required discharge of water to flow under them without interference4 ,but if1 owing to an increase of head caused by a rise in the upstream water-level1 the water tends to rise higher at the circumference of the chamber1 then the water at the surface of the stream strikes against the diaphragm plates1 and its centrifugal force being absorbed1 it will fall in towards the centre just as happened in the teacup when the spoon was used in place of these plates4 ,in this way the excess head that caused the additional rise of water at the circumference is used up by the fall back towards the centre4 ,the full capacity of the semicircle or spiral for using up excess head or energy in this way is made available by the use of a sufficient number of diaphragm plates fixed at suitable intervals4 ,when the range of head to be dealt with is not large1 then a semicircular chamber is sufficient2 but for large ranges of head the chamber is made of spiral form so as to lead the water round a complete revolution or more1 as may be necessary4 ,,structural ,,details4 ,fig4 #bi shows the general form and structure of the type of module suitable for irrigation4 ,fig4 #cj is from a photograph4 ,the working chamber or shell ,a is constructed of mild steel plating securely riveted to a framework of angle steel1 and the semicircular form of the shell with the rigid diaphragm plates ,b ,b riveted to the walls makes a very strong structure1 and ensures durability4 ,the 8leading-in0 bend ,c is of cast iron strongly bolted to the steel shell1 and is so designed as to deliver the water into the module chamber in a completely established vortex condition4 ,the socket ,d on this 8leading-in0 bend is made so as to allow of considerable latitude in the vertical alignment of the straight leading-in pipe1 so that the water can be drawn from any desired depth in the parent channel1 and the proportion of silt drawn off is thus brought under control4 ,illustration3 -- ,,end ,,elevation4 -- -- ,,plan4 -- -- ,,front ,,elevation4 -- ,,fig4 #bi4--;,details of ,gibb's ,patent ,module4 ,grooves ,e ,e and a shutter ,f1 as illustrated1 for closing off the flow through the module1 are provided1 if required1 but all modules are not fitted in this way1 because many irrigation authorities consider it undesirable to provide the consumers with unrestricted facilities for closing off their supplies without previously giving notice of such an action4 ,illustration3 ,,fig4 #cj4--,the ,completed ,module 7,open ,type for ,low ,heads74 ,an escape notch ,h is provided in the position indicated when desired4 ,it may1 however1 be found difficult to determine beforehand the upstream water-level at which it is necessary to allow this escape of surplus supply1 so that it is generally more satisfactory to cut the escape notch after the modules have been installed and actual experience has indicated a suitable level for the notch crest4 ,in the standard type of module for irrigation purposes the top of the module chamber is completely open1 as shown1 and this is the type generally recommended1 as it is found that consumers have greater confidence in an apparatus which hides nothing from them4 ,to meet the needs of special cases1 however1 a second type is also made in which the chamber is completely closed and considerably reduced in height1 being thus specially suitable for sites where space is confined4 ,pipes ,i1 of diameter suitable for all sizes of modules1 are also supplied4 ,these may either be welded steel or cast iron1 as desired4 ,an #ah-;feet length of pipe is usually found sufficient to bring the supply through the canal bank to the module4 ,all modules supplied are treated with anti-corrosive paint1 which ensures the protection of the metal4 ,,appendix ,k4 ,,kennedy',s ,,gauge ,,outlet4#ff 7,see p4 #afh47 #ff ,see ,punjab ,irrigation ,branch ,paper ,no4 #ab1 8,results of ,tests of ,kennedy's ,gauge ,outlet40 ,,fig4 #ca shows a bell-mouthed orifice discharging into an air-space4 ,the jet springs across the air-space and traverses a gradually diverging tube4 ,let a1 ,a be the sectional areas of the stream at the air-space and the downstream end of the tube respectively1 and let ,v1 v1 and ,p1 ,p be the corresponding velocities and pressures4 ,let resistances be neglected4 ,since the pressure in the air-space is ,p1 ,v 7#b;g h7 or the discharge through the tube depends only on h and not on h4 ,illustration3 ,,fig4 #ca4 ,by ,bernouilli's theorem1 ,v ,p v ,p ---- ---- ----- -- #b;g ,w #b;g ,w or ,p - ,p ,v - v --------- ---------4 ,w #b;g ,this quantity 7since v is small7 is not much less than h or ,v_/#b;g4 ,in other words1 the water levels of two cisterns with an air-space between them differ only a little1 or h is small4 ,the above case 7two cisterns and air-space7 is mentioned in ,hydraulics1 ,chap4 ,v4 ,the principle is simply that the velocity head at the air-space is reconverted into pressure head by passing the stream through a gradually diverging tube4 ,in the absence of such a tube the velocity head would be wasted by causing eddies in the downstream cistern4 ,if the downstream cistern is a watercourse whose water-level is considerably lower than that of the upstream cistern or distributary1 ,v is obviously unaffected4 ,also ,p is obviously reduced4 ,therefore1 by ,bernouilli1 v is increased1 or the stream does not fill the expanded tube and there are eddies in the tube4 ,the water-level in the watercourse may even be lower than the end of the tube4 ,the discharge is unaffected4 ,in practice there are1 of course1 resistances1 but this fact does not affect the general conclusions stated above4 ,the minimum working head 7difference between the two water-levels7 which gives a constant discharge is greater than would be the case in the absence of resistances4 ,this 8minimum working head for modularity0 has been found to be #ba foot1 #db foot1 and #fa foot1 the corresponding values of the 8depression10 h1 being respectively #a foot1 #b feet1 and #c feet4 ,when the working head is less than the above1 the discharge is less and it depends on the working head4 ,the depression should1 according to ,kennedy1 be about #age feet1 but it may be more4 ,the chief difficulty in using the gauge outlet as a module is that the air vent can be stopped up4 ,this converts the apparatus into a compound diverging tube 7,hydraulics1 ,chap4 ,,iii41 ,art4 #ag74 ,the discharge is1 of course1 increased1 and it becomes dependent at all times on the working head4 ,another difficulty is that any rise or fall in the water-level of the distributary 7and such rises and falls may occur owing to silting or scour1 however carefully the discharge may be regulated7 alters the discharge somewhat1 though not to the same degree as in an ordinary outlet with a working head of1 say1 #e foot4 ,in short1 ,kennedy's gauge outlet1 or 8semi-module0 as it is sometimes called1 can modify but not do away with the variations of the discharges of outlets4 ,,index4 ,absorption1 #af1 #aei4 ,alignment1 principles of1 #d4 ,alignment1 centrality in1 #e4 ,alteration in line1 #ei4 ,assiut ,barrage1 #aa4 ,assouan ,dam1 #aa4 ,banks1 construction of1 #ach4 -- protection of1 #aci1 #age1 #agh4 -- width and height of1 #ef4 ,banks and ,roads1 #ec4 ,basin ,irrigation1 #aa4 ,berms1 #ec4 ,bifurcations1 #dg4 ,bifurcation1 head needed at1 #de4 ,borrow pits1 #ee4 ,branches of ,canals1 #c4 ,breaches in ,banks1 #agf4 ,bricks used for canal work in ,india1 #hh4 ,bridges1 #h1 #hj1 #hg1 #acj4 -- ,skew1 #bi1 #db4 ,bushing of banks1 #agh4 ,canal and branches1 #bj1 #dg4 ,canal1 bed width of1 #ea4 -- supplied from reservoirs1 #c1 #ac4 -- inundation1 #a1 #de1 #gi1 #abg1 #aef4 -- perennial1 #a4 ,capillarity1 #af4 ,cattle ,ghts1 #ha1 #agc4 ,cement for lining channels1 #afj4 ,chainage1 #ic1 #aah4 ,channels1 alterations in1 #ig4 -- enlargement of1 #ig1 #aci4 -- gradients of1 #ej4 -- side slopes of1 #eb4 ,colonization ,schemes1 #fd4 ,command1 #b4 ,commanded area1 #d4 ,contour lines1 #cg4 -- plan1 #bf1 #cf1 #fc4 -- survey1 #cg4 ,crops1 failure of1 #ajc1 #adb4 -- kinds of1 #aja4 ,culturable commanded area1 #bf1 #aac4 ,curves and bends in channels1 #h1 #aci4 8,delta10 #bb1 #aaj4 ,deputy ,collector1 #if4 ,designs and ,estimates1 #fj4 ,design of canals1 #b1 #bf1 #cj1 #dg1 #adg1 #aef4 ,discharge of canal during rabi1 #eb1 #aah4 ,discharge observations1 #ajg4 ,discharges of ,punjab rivers1 #ade1 #aeg4 ,discharge tables1 #ajf4 -- through an outlet1 #fa4 ,distance marks1 #ic4 ,distribution of water1 #ad1 #aah1 #abe4 ,distributaries1 #c1 #bj1 #dd1 #df4 -- best system of1 #ga4 ,distributary1 bed width of1 #fh4 -- design of1 #fj4 -- height and width of banks1 #fh4 -- kharif1 #aef4 -- longitudinal section of1 #fi4 -- major and minor1 #da4 -- off-take of1 #ea4 -- remodelling of1 #abh4 -- side slopes of1 #fi4 -- strip of land for1 #fi4 -- with three fourths full supply1 #de1 #fh1 #aff4 ,divide ,walls1 #cc1 #afi4 ,divisions1 canal1 #if4 ,drainage1 #aj4 ,drainage ,crossings1 #h1 #aef4 ,duty of water1 #ba1 #be1 #ci1 #adh1 #aec1 #aed4 ,duty1 improvement of1 #bd1 #ajb1 #aeh4 ,eastern ,jumna ,canal1 #ca4 ,efflorescence called 8,reh10 #ae4 ,egypt1 irrigation in1 #aa4 ,embankments1 #i1 #cc1 #aef4 ,escapes1 #i1 #ajj1 #ahj4 ,estimates for work1 #ei4 ,evaporation1 #af4 ,executive ,engineer1 #if4 ,extensions of canals1 #abg4 ,extra land1 #eh4 ,falling ,shutters1 #cb4 ,falls1 #h1 #ha1 #hg4 -- incomplete1 #hg1 #acj4 -- notch1 #hf4 ,field book1 #aja4 -- map1 #aja4 -- register1 #aja4 ,final line1 #ei4 ,flow and lift1 #aa4 ,full supply duty1 #fd4 ,full supply factor1 #fd4 ,ganges ,canal1 #ca4 ,gauges1 #aj1 #ajc1 #ajd1 #ahc4 ,gauge reader1 #if1 #ih1 #aje1 #ahd4 ,gauge reading1 #aje1 #aba4 -- register1 #aje1 #ajf1 #ajh1 #aaa4 ,gibb's module1 #afd1 #ahf4 ,guide banks1 #ce4 ,head for distributary1 #hb1 #hc4 ,headworks1 #b1 #cj1 #ih1 #ii1 #acg4 ,indents for water1 #ih1 #ajh1 #aaj4 ,inundation canals1 #a1 #de1 #gi1 #abg1 #aef4 ,irrigation boundaries1 #cc1 #abi4 -- in various countries1 #a4 -- registers1 #aac4 -- unauthorised1 #aja4 ,kennedy's gauge outlet1 #afh1 #aic4 -- ,rules for channel design1 #dh4 ,kharif or ,summer ,crop1 #bc4 ,kutter's co-efficients1 #ea4 ,lift irrigation1 #aa1 #adb4 ,lime for making channels watertight1 #afb4 ,longitudinal section1 #fi1 #acj4 ,losses of water in channels1 #af1 #ch1 #aei4 ,low supplies1 #aah1 #abc4 ,lower ,chenab ,canal1 #be1 #add4 ,lower ,egypt1 #aa4 ,lower ,jhelum ,canal1 #add4 ,maintenance work1 #ach1 #aga1 #agd4 ,marginal ,embankments1 #i4 ,masonry works1 #bi1 #hj1 #hi4 -- -- large scale site plan1 #hi4 -- -- type designs1 #hi4 ,mills1 #h4 ,minors1 question of desirability of1 #ge4 ,modules1 #afb1 #ahf4 ,navigation1 #ab4 ,needles and horizontal planks1 #he4 ,oil for lining channels1 #afj4 ,older ,indian canals1 #aj1 #fh1 #ih4 ,outlet1 discharge of1 #fa4 -- registers1 #aac4 ,outlets1 #ae1 #fa1 #ff1 #fg4 -- applications regarding1 #adj4 -- design of1 #gf4 -- on inundation canals1 #gi4 -- on older canals1 #fh4 -- positions of1 #fe4 -- remodelling of1 #aca4 -- register of1 #aac4 -- size of1 #aad1 #acd4 -- temporary1 #gh4 -- variability of duty on1 #ff4 ,parapets1 width between1 #gg4 ,patwari1 #if1 #aja4 ,percolation1 #af4 ,perennial ,canals1 #a4 ,pitching1 #ij4 ,plan1 large scale1 #ei4 ,postal system1 #ig4 ,profile walls1 #ia1 #id4 ,project1 sketch of1 #bf4 ,proportion of land to be irrigated1 #bg1 #aef4 ,puddle for lining channels1 #afj4 ,punjab1 projects for canals in1 #add4 ,punjab rivers1 #ade1 #adg4 ,quarters for regulating staff1 #hh4 ,rabi or winter crop1 #bc4 ,railings1 #hh4 ,rain1 #i1 #bb1 #ajj4 ,ramps1 #hh4 ,ratio of bed width to depth1 #ej4 ,reduction in size of channel1 #abh4 ,registers1 irrigation1 #aac4 ,regulation of supply1 #ajc1 #aba1 #abg4 ,regulators1 #g1 #hj1 #hd1 #ahd4 -- permissible heading up1 #he4 ,remodellings of channels1 #abg4 -- of outlets and watercourses1 #aca1 #acd4 ,rest ,houses1 #ie4 ,reservoirs1 #ac4 ,rules for designing canals1 ,kennedy's1 #dh4 ,scheme1 cost of1 #bh1 #ei4 ,sides1 falling in of1 #aci4 ,sidhnai canal minors1 #da4 ,silt1 clearance of1 #ig1 #ach1 #aci4 -- deposit1 #ae1 #ig4 -- trapping at ,headworks1 #dg4 ,silting and scouring1 #ae1 #dh1 #ih1 #aci4 ,sirhind ,canal1 #ai1 #add4 -- -- silting in the head reach of1 #ih4 ,soil1 water-logging of1 #aj1 #bd1 #ajb4 ,spoil ,banks1 #eb1 #eg4 ,subdivisions1 canal1 #ie4 ,subdivisional officer1 #if4 ,suboverseer1 #if4 ,superintending ,engineer1 #if4 ,supply carried1 #ajj4 -- distribution of1 #ad1 #aah4 -- mean and full1 #bg1 #df1 #abb4 -- regulation of1 #ajc1 #ajd1 #ajf1 #abg4 ,syphons1 #g1 #ga1 #hg1 #aha4 ,tailing of one channel into another1 #dj4 ,telegraph1 line of1 #ig4 ,training of rivers1 #cc4 ,trial lines1 #eh4 ,trial pits1 #eh4 ,triple canal project1 #add4 ,tunnels1 #ac4 ,turns1 or rotational periods of flow1 #ad1 #aah4 ,type cross sections1 #ef4 ,under-sluices1 #cb4 ,upper ,bari ,doab ,canal1 #ai1 #add4 -- ,chenab ,canal1 #cc1 #add4 -- ,egypt1 #aa4 ,upper ,jhelum ,canal1 #ej1 #add4 ,velocity1 #ab1 #ej4 ,village lands1 #fb4 ,watching banks1 #age4 ,water1 payment for1 #ab1 #ajj1 #ajb1 #adb1 #adc4 ,water level1 fluctuation in1 #ajj1 #abd4 ,watercourse1 limit of size of1 #gd4 ,watercourses1 #d1 #bj1 #fe4 -- applications regarding1 #adj4 -- for trees1 #eh4 -- remodelling of1 #aca4 -- with poor command1 #fg1 #acc1 #aff4 ,waterings1 #aa1 #bd4 ,water-logging of the soil1 #aj1 #bd1 #ajb4 ,wave1 travel of1 down a channel1 #abd4 ,western ,america1 canals in1 #ab4 -- ,jumna ,canal1 #ca1 #ci4 ,wing ,walls1 #hi4 ,works1 arrangement of1 #hi4 -- two or more close together1 #hi4 -- urgent repairs of1 #acg4 ,zilladar1 #if4 ,harvey ,healing1 ,printers1 ,manchester ,street1 ,cheltenham4 ,transcriber's ,notes ,the inconsistent use of periods after ,roman numerals has been retained2 other inconsistencies 7spelling1 hyphenation1 formatting and lay-out7 have been retained as well1 except when mentioned below4 ,depending on the hard- and software used and their settings1 not all elements may display as intended4 ,some of the tables are best viewed in a wide window4 ,page #ba3 ,the equation does not agree with the calculations given4 ,page #ff1 ,fig4 #aa3 ,there are two illustrations labelled ,fig4 #aa1 the hyperlinks point to the appropriate illustration4 ,changes made ,obvious typographical errors have been corrected silently4 ,footnotes and illustrations have been moved out of text paragraphs4 ,some tables have been re-arranged or split2 in several tables1 the data alignment has been standardised4 ,page #ah1 table1 ,total of second column3 #hic changed to #hja ,page #ci3 ,kutters changed to ,kutter's ,page #ic3 marked out changed to marked at ,page #fi3 #c ,depth of digging changed to #ac4 ,depth of digging ,page #aji1 first average #a changed to #da ,page #aag3 ,net ,areas ,irrigated in ,areas changed to ,net ,areas ,irrigated in ,acres ,page #aej3 ,cusecs4 added as in similar tables ,index3 ,cattle ,ghats changed to ,cattle ,ghts2 ,line for making 444 changed to ,lime for making 4442 ,lower ,chenal ,canal changed to ,lower ,chenab ,canal4