THE 1RRIGA Tl ON A GE. 395 



super- passages are necessarily very deep, and are always much below 

 the subsoil water or spring level. Consequently, pumping to a very 

 great extent, and sometimes for a long time, has to be carried out 

 both before and during the construction of the foundations; entailing 

 heavy expenditure. 



Thus to counterbalance the smaller cost of the head and river 

 works, there is the greater cost of the main canal channel, the long 

 time occupied in its construction, and the heavy annual maintenance 

 charges, besides the great inconvenience, or even danger, that would 

 ensue on the failure or destruction of any syphon or super-passage, 

 or the breaking into the canal of any torrent. Consequently, for the 

 later designed large canals, such as the Chanab and Jhelam Canals, 

 the sites for the head works have been selected much lower down the 

 courses of the rivers, where there are no hill torrents to be crossed, 

 and where, as the river bed is not very deep below the ordinary 

 ground level of the land bordering it, the depth of excavation is not 

 excessive, and there are no special difficulties to be overcome in the 

 construction of the main canal. Though the length of the weir across 

 the river is great, nearly a mile in the case of these two canals, and 

 long lengths of strong earthen embankments are required, with much 

 stone or brushwood pitching (or riprapping) on their slopes, wherever 

 they have to meet the force of the stream, yet on the whole there are 

 no special difficulties of construction or maintenance. Earthwork 

 also in India is done very cheaply and rapidly; and thus, this system 

 is found to be more satisfactory and to give less trouble, than the 

 former one of keeping hill torrents under control, conducting the 

 waters across the canal, and seeing them safely off the premises and 

 on their way into the river. 



Both the Sirhind and Bari Doab Canals are now valuable proper- 

 ties and sound investments, bringing in to the government a hand- 

 some net revenue, after paying all expenses of working, maintenance, 

 and annual interest on the capital cost of their construction. As they 

 commence at the foot of the hills, they first traverse for some 60 to 

 80 miles, the belt of country in which in most years of average rain- 

 fall, no irrigation is necessary, though here some irrigation is done 

 by cultivators who grow the more valuable crops which require many 

 or frequent waterings. The demand for water is comparatively small 

 in ordinary years in these upper reaches of the canal; but should the 

 rainfall be deficit, or too long delayed, the demand suddenly becomes 

 great: and as it can be supplied, the area irrigated, and the revenue 

 derived from the water rates assessed, are largely increased. The 

 revenue of the canal in this tract may thus vary very considerably 

 from year to year. South of this belt where cultivation is precarious 

 or impossible without irrigation, the demand is always great, but may 



