THE FLOW OF WATER 1-N IRRIGATION CHANNELS. 41 
cemented except at the sides, where the velocity (mean 1.57 feet per second) is not 
sufficient to prevent silt from depositing. A dense growth of grass killed the velocity 
for about one-half foot from the banks, which were quite vertical and are typical 
of the old ditches in Colorado and Utah. Coefficient n=0.0267. 
No. 204, Expt. S-66, Fullerton Ditch of the Anaheim-Union Water Co., California. 
Station of the reach tested is at the lower end of a gentle curve (PI. XV, fig. 3), while 
about 100 feet below station 6 there is an angle of about 80° to the right which checks 
up the water so that a correction for change in velocity head was necessary in com- 
puting the value of n. Grass and moss kill the velocity for about 1 foot from the banks, 
while the bed of the canal is a hard, cemented, sandy loam soil, with about 0.1 foot of 
shifting sand. This canal was under exactly the same conditions as No. 172, except 
that this needed cleaning and the other one had just been cleaned. The difference in 
value of n is about what should be expected and shows the value of cleaning. Coeffi- 
cient n=0.0269. 
No. 205, Expt. S-86, Farmers' Canal, near Boulder, Colo. When tested this ditch 
was carrying about half its capacity. It is constructed along a gently curving hillside. 
Willows and grass form a dense fringe at the sides, while the bottom, originally con- 
structed in red mountain soil mixed with fragments of sandstone, now has a rather 
hard, gravelly bottom, with angular fragments rather than rounded pebbles. The 
section is irregular, and the value of n is quite comparable with that of a cobble- 
bottom ditch, although this reach is not cobble bottomed. Coefficient n=0.0270. 
Nos. 206, 207, and 208, Expts. H-12 a, b, and c, lateral 2, Billings Land & Irrigation 
Co., Montana. These tests are on an irregular section of small lateral, constructed in 
loamy earth. It is now fringed with grass, which trails somewhat, though newly 
mowed. The discharge was varied for the various tests. The bottom is irregular, 
with drifting sand throughout most of the reach. The canal is too irregular to concede 
too much weight to the various values of n found. 
No. 209, Expt. S-60, Yosemite Power Co.'s Ditch. This ditch follows a moun- 
tain contour in disintegrate d-rock soil. A fringe of bushes and grass retard velocity 
at the banks, while the bottom is porous and gravelly with scattered bowlders and 
rock fragments up to two-fist size. The value of n is about what may be expected of 
a cobble-bottom ditch, although this one does not strictly class as such. Coefficient 
n=0.0274. 
No. 210, Expt. S-5, lateral of Parley's Ditch, Utah. This test is on a straight 
reach in gravelly loam soil. A fringe of grass retards velocity for about one-half foot 
from the banks. The bottom is composed of clean sand which yields about 0.1 foot 
to the feet, in wading. A slight wind upstream makes the value of n a little high. 
Discounting the wind, this value would be about that of test No. 209 above. Coeffi- 
cient n=0.0278. 
No. 212, Expt. S-20, lateral of South Side Twin Falls Canal, Idaho. This reach of 
ditch is on a gentle contour curve of about 400 feet radius. Constructed in hardpan 
underlying about a foot of lava-ash soil, the water section is quite slick but is badly 
washed in longitudinal gullies. The banks, too, are irregular and fringed with a 
dense growth of grass and alfalfa. Coefficient n=0.0283. 
No. 213, Expt. S-85, lateral 10 from Arizona Canal, Salt River project, United 
States Reclamation Service, Arizona. This test is on a straight reach of small ditch 
on a steep grade. Constructed in a silt loam soil, the high velocity has washed very 
irregular gullies and pockets. An average growth of grass and weeds also retards 
velocity. (See PI. XVI, fig. 1.) Coefficient n=0.0284. 
No. 215, Expt. S-79, Beech Canal, Imperial Water Co. No. 1, California. This 
test is under exactly the same conditions as those described in No. 162, with the 
exception that a longer time has elapsed since the dense growth of grass shown on 
Plate XVI, figure 2 was cut.- The difference in grass condition is noted by compar- 
ing the above view with that in Plate XI, figure 2. Coefficient n=0.0290. 
