2 3 8 



UNIVERSITY OF COLORADO STUDIES 



i .811 . ,, . .00281 

 + 41 .66 + — - — 



+ M 4i - 66+ 



.0028 



'-) 



VrV s 



where C, R and S are as given above and n is a "coefficient of 

 roughness" of the stream bed. Kutter proposed values of n for 

 different materials among which were the following: 



(1) Canals in fine gravel n — 0.020 



(2) Canals and rivers free from stones and weeds n = 0.025 



(3) Canals and rivers in bad order n = 0.035 



Of all the values which he suggested, these are the only ones that 

 would be applicable to ordinary irrigation ditches. The factor n= o . 025 

 has been very generally used, but some large ditches as well as some 

 smaller ones designed on this basis have given very unsatisfactory 

 velocities, in some instances so swift that the washing was serious and 

 in others so sluggish that silt was deposited and vegetation flourished in 

 the channel. 



Several attempts have been made to secure more suitable values of 

 n, among which the experiments of P. J. Flynn, C.E., of Denver and 

 those of Professor Samuel Fortier of Bozeman, Montana, stand foremost. 

 The results of the very valuable experiments of the latter are published 

 in Water Supply and Irrigation Paper No. 43 of the United States 

 Geological Survey. He classified the experiments on canals into eight 

 groups which are briefly tabulated below. 



Group No. i 



w = o.oi34 to 0.0184 



The channels were elliptical in form and had been in use from six to thirty years. 



Character of Channel 



Clayey loam, well lined with silt. Good condi- 

 tion. Free from vegetation 



Ditto 



Ditto 



Ditto 



Ditto 



Fine gravel, sides fair condition 



Sides smooth; earth and gravel; no vegetation 



.0134 

 •0135 

 ■0137 

 •OIS5 



.0164 



.0177 



.0184 



