EXAMPLES 865 



determine the percentage loss in transmission if the difference of level 

 between the supply reservoir and tail race is 500 feet. C = 127*6. 

 Answer. Gradient 1 in 162*9. 



Loss of energy = 32*4 per cent. 



(3) A flat-bottomed channel is required to have a constant velocity of 

 flow for all depths of water. The bottom breadth is 5 feet. Determine 

 the depth at a section where the breadth is 20 feet, if the hydraulic mean 

 depth is 1*25 feet. C = 60. 



Answer. 4*35 feet. 



(4) The original depth of a wide stream is 3 feet, and the slope of its 

 bed is 1 in 1,000, the value of /being *0131, C = 70. A dam 10 feet high 

 is erected across the stream. Determine the rise in the water level 

 immediately behind the dam and at points J and 1 mile up stream. 

 (Assume the coefficient of discharge for the dam to be *560.) 



Answer. Eise behind dam = 9'28 feet. 



J mile up stream = 6*87 feet. 

 1 =4*04. 



(5) It is required to excavate a canal out of rock to be of rectangular 

 section and to bring 500 cubic feet of water per second from a distance of 

 4 miles with a velocity of 7 J feet per second. Determine the gradient and 

 the most suitable section for the canal. Take C = 150. 



Answer. Section 11*54 feet wide, 5*77 feet deep. 

 Gradient 1 in 1,156. 



(6) In carrying out field operations to determine the discharge of a 

 river, a straight reach 500 feet long is available. The slope is approxi- 

 mately Toioo* an d the levelling is possibly accurate within ^J n foot. The 



ssible error in determining the wetted perimeter is 8 per cent., and in 

 determining the mean sectional area is 5 per cent. To what degree of 

 accuracy are the final results likely to approximate. 



Answer. Within about 13J per cent. 



(7) The value of / for a stream having a slope of I( }Q O is "0050. 

 Normally, the stream is of depth 4 feet and breadth 60 feet, but is passed 

 through a sluice having an opening 2J feet deep. Determine whether the 

 conditions are such as to lead to the formation of a standing wave, and if 



determine the probable height of the crest of this wave above the upper 

 ige of the sluice. 



Answer. Yes. *93 feet. 





