Quantity of Water Consumed in Irrigation. 47 

 From the foregoing the following average depths are obtained : — 



Case A 

 Case B 



Qa 



mill. c. ft. 

 192 

 192 



M. 



100,000 

 60,000 



Loss per M 



per diem = 



Qa -T- M. 



eft. 

 1921 

 3202 



Depth lost per diem 

 (d) = Q a -^ 5280 M. 



feet. inches. 

 •3638 = 4-366 

 •6C64 = 7-277 



These are the average depths over the whole wetted surface in cases 

 A and B respectively, lost by percolation (see par. 16). 



APPENDIX C. 



Calculation of the Loss of Water by Percolation in the 



FIRST PART OF THE GANGES CaNAL. 



(For Symbols, see Appendix B.) 



The volume of water (D) passing down the canal in December, 1860 

 (see "Pro. Inst. Civil Engineers," vol. 27, p. 509), was found to be 



at the head, Hardwar, 6710 c. ft. per second, and at Roorkee, 



6283 c. ft. per second, giving a loss of 427 c ft. per second in this 

 length of about 18 miles. The loss really took place in 15 miles, or 

 probably less, where beds of sand and boulders are crossed. The 

 depth of water in the canal was from 8J ft. to 9 ft., making w = 175 

 ft. Then w = 15 X 5280 X 175 = 13-86 mill. sq. ft., and Q a = 427 

 X 86,400 = 37 mill. c. ft. .-. d = Q a -r- w = 37 -f- 1386 = 2*66 ft. 

 At the Ratmu river it must have been much more — probably over 

 3 feet. 



At the same time, 31 miles below Roorkee, D = 5279 c. ft. per 

 second, showing a further loss of 1004 c. ft. per second. A portion of 

 this was used for irrigation, though probably not more than 400, or, 

 say, 500 c. ft. per second. The larger quantity would leave 500 c. ft. 

 per second as the loss by percolation in the 31 miles, giving an average 

 depth (d) of a little over 1^ ft. daily ; though, owing to the consumption 

 for irrigation being uncertain, this result is open to question. 

 Between the 30th and 40th miles, where a sandy tract of country is 

 crossed, the depth would be in excess of the average, and doubtless 

 fully l| ft. 



