42 BULLETIN 194^ U. S. DEPARTMENT OF AGEICULTUBE. 



No. 216, Expt. S-49, Wheeler Ditch, Nevada. This test was made on a ditch 

 following a contour in curves of from 300 to 500 feet radius. While the bottom is hard 

 many bowlders of several hundred pounds weight border the channel, and a few have 

 rolled into it. A dense growth of grass and bushes fringe the sides, and a fine, dense 

 moss retards velocity for about 0.3 foot from the bottom. Coefficient n=0.0292. 



Nos. 219 and 220, Expts. H-13c, lateral of Billings Land & Irrigation Co., Montana. 

 These tests were made on the same reach of canal but with varying discharges, and 

 for No. 219 grass fringing the edges was cut, hence removing some of the retarding 

 influence present in No. 220. The bottom is covered with fine, deep, shifting sand, 

 80 "quick" that a wading man sinks about 1 foot. 



No. 221, Expt. S-59, main canal, Modesto Irrigation District, California. This test 

 was made on a wide canal with but a small portion of its total capacity running. This 

 gave a condition of shallow water flowing over gullied hardpan having about 0.1 feet 

 of shifting sand. No grass touched the water at this stage. Coefficient n=0.0300. 



No. 222, Expt. S-72, Upper Canal, Riverside Water Co., California. This test was 

 on a straight reach of canal originally excavated in a sandy loam soil. At present the 

 bottom is covered with a bed of fine sand which remains quite hard until disturbed, 

 when it cuts rapidly. Dense grass along the sides and scattered patches of moss in 

 the canal cause a high value of n. Coefficient n=0.0315. 



No. 223, Expt. S-77a, Lower Canal, Riverside Water Co., California. Though orig- 

 inally excavated in a clean-cut section of soft hardpan, the present condition of this 

 reach is much less efficient, due to a deposit of shifting sand and growths of water 

 grasses and dense grass along the edge, though not so bad as in No. 224 below. Co- 

 efficient 71=0.0318. 



No. 224, Expt. S-77b. Same canal as No. 223 above, but the grass along the edge 

 kills velocity for about 1 foot from both banks. Otherwise the same general condition 

 holds as before. This reach adjoins the other reach at a right-angled bend shown in 

 Plate XVI, figure 3. Coefficient n=0.0360. 



No. 228, Expt. S-9, Lower Canal from Big Cottonwood Creek, Utah. This test was 

 made on a ditch which would have an efficient carrying capacity with a small amount 

 of labor, but through neglect willow roots and grass have so encroached on the channel 

 that a high value of n is obtained. Originally constructed in a sandy loam soil, the 

 bottom was quite hard with no cobbles but with a deposit of soft mud in the lower 

 velocities near the sides. The reach tested is on a gentle contoiir curve, which exerts 

 an inappreciable influence when compared with the vegetable growth. The banks 

 are quite vertical and irregular, like most rooted channels. Coefficient n=0.0324. 



No. 230, Expt. S-62, Golden Rock Ditch, Yosemite Power Co., California. This 

 reach tested follows a gentle mountain contour. The bottom is of clean disintegrated 

 slate with scattered pieces to two-fist size. Although this bottom has a great retarding 

 influence, the value of n is higher than is to be expected. There was but little grass 

 touching the water. Coefficient n=0.0346. 



No. 231, Expt. H-15, lateral 1, Billings Land & Irrigation Co., Montana. This 

 reach of ditch is in sandy loam fill. The water section is irregular with sand in the 

 bottom and a little trailing grass and moss. Coefficient 71=0.0349. 



No. 233, Expt. S-18, Logan and Hyde Park Canal in Logan, Utah. This straight 

 reach of canal (PI. XVII, fig. 1) was originally constructed in gravelly soil with many 

 cobbles from egg to two-fist size. At the time of the test the edges were irregular and 

 densely grassed, with patches of moss and some cobbles scattered throughout the 

 reach. The moss lies usually within 0.3 foot of the bottom. Coefficient 7i==0.0364. 



No. 235, Expt. S-53, lateral 2^, Turlock Irrigation District, California. This test 

 is a straight reach of canal excavated in hardpan requiring blasting. This leaves the 

 section rough and pitted. The bottom was covered with about 3 inches of rough, 



