THE FLOW OF WATER IN" IRRIGATION CHANlSrELS. 31 



found. This sand -was about 0.03 foot deep. The clear water emerges quietly from 

 the lower end of a siphon under a road about 100 feet above station 0. The canal turns 

 at right angles, without curvature, about 100 feet below station 6. However, the 

 depth at the various cross sections remains quite constant, showing that the water was 

 not appreciably checked up by this turn. As shown in Plate III, figure 3, there was 

 a verj' slight retarding effect due to grass and weeds dragging on the surface of the 

 water near the edges of the channel. Coefficient n=0.0188. 



Xo. 44, Expt. S-67, Arroyo Ditch & Water Co.'s main canal, near Whittier, Cal. As 

 shown in Plate IV, figure 1, this rough-finish concrete section has accumulated a 

 deposit of rough mossy growth that greatly retards the velocity of the water. In a 

 few places throughout the reach tested the lining was irregular and not in true align- 

 ment, which also tended to increase the value of n. The reach was on tangent, with 

 a sharp angle about 50 feet above station and a gentle curve about 100 feet below 

 station 10. See discussion under Nos. 35, 40, and 42, above. Coefficient n=0.0188. 



Nos. 45 to 50, Expts. S-31, S-30, S-32, Cenlial Oregon Irrigation Co.'s North Canal 

 near Bend, Oreg. These experiments were conducted with varying discharges, on 

 consecutive days, in identical reaches; (a) is on a tangent 240 feet long between a 

 15° curve above and a 14° curve below; (6) embraces 157 feet of tangent, then 154 feet 

 of 14° ciu^-e to the right, then 90 feet tangent, then 109 feet of 15° cmve to the left, 

 then the tangent that includes (a) 240 feet long, then 178 feet of 14° curve which passes 

 into a very rough lava-rock cut about 200 feet below station 10 plus 26. 



This lining is a clean-scoured, very rough, and deeply pitted concrete made in a 

 rough lava-rock cut. As shown on Plate IV, figure 2, the cross sectional form is even 

 and the filaments of current are not disturbed except by the curves, but the inherent 

 roughness of the lining accounts for the high values of n. The grade of the bottom of 

 this canal was constructed 0.001 feet per foot. 



This lining was a 1 : 4 : 5 mixtiu-e, deposited behind shiplap forms against a hand- 

 laid rock wall, filling the cavities in a rough rock cut. Expansion joints of I by 4-inch 

 lumber were placed on sides and bottom every 12 feet and left in the concrete. 



No. 51, Expt. S-38, main canal. South Orland project. United States Reclamation 

 Service, California. As shown in Plate IV, figure 3, this lined section comes between 

 two earth sections of the canal. The concrete is quite rough and pitted, with slight 

 growths of moss, but not nearly sufficient to account for the high value of n found. 

 The writer can only account for this value because of retarding influences due to the 

 earth channel below the lined reach. Coefficient n==0.0211. 



No. 53, Expt. S-C8, smail ditch from pumping plant, California. Although con- 

 structed with a smooth-finished cement wash, this ditch shows a high value of n 

 because a dark, crinkly deposit has changed the condition of the walls. Vegetation 

 on the banks dragged in the water and retarded velocity to a slight extent (PI. V, fig. 1.) 

 This test is not given full weight because the ditch is too small to give a first-class 

 current-meter measurement. The mean of three measurements was used. Coeffi- 

 cient n=0.0220. 



No. 54, Expt. S-75, Riverside Water Co.'s Lower Canal, Riverside, Cal. This experi- 

 ment gives a good example of a cement-wash lining in which under favorable con- 

 ditions in southern California a friction factor of about 0.018 might be expected with- 

 out eraflicating the sand whicli appears to be ever present in the canals in this vicinity. 

 If the sand were removed by the addition of numerous sand sum])s and gates this 

 factor would be redured to 0.010 or thereabouts. At the time of making the tests on 

 thi« canal, a.H shown in Plate V, figure 2, the lining had been broken in scattered 

 Bj)OtM, allowing vegetation to root and grow. In tlie Ijottom of tlie channel were 

 wattered depo.Hit^ of loose sand, covering poKHildy 10 per cent of the bottom area. In 

 Bome of tlujHC deposit/) rncws and water graHwes flourislMjd. A gentle curve atM)ut 100 

 feet above station had little or no influence on llie flow in the low velocities on- 



