30 BULLETIN 194^ U. S. DEPARTMENT OF AGKICULTUEE. 



No. 35, Expt. S-69,'Sanderfer Ditch Co.'s main canal, near "WTiittier, Cal. As 

 shown in Plate II, figure 3, this reach is straight and quite uniform. The bottom is 

 slightly dished. As is the case of all small lined ditches in southern California, the 

 sides and bottom are covered with a rough deposit which entirely vitiates the good 

 results which would be anticipated by using a smooth cement wash such as the one on 

 this ditch. This deposit appears to accumulate on either smooth or rough concrete, 

 60 the added expense of the former does not appear to be warranted in view of the 

 results. The water in this ditch was clear and did not carry an appreciable amount of 

 sand. Coefficient n=0.0155. 



No. 37, Expt. S-37a, lateral 12, Orland project. United States Reclamation Service, 

 central California. This is a small lined section of general trapezoidal form, but with 

 a slight dishing in the bottom. About 50 feet above station is the lower end of a 

 chute drop, and the ditch below station 2 plus 06. turns to the right 90° in a curve of 

 84 feet radius. The surface of the channel was a good grade of concrete, but not 

 smooth washed. There was a slight deposit of slimy silt, which would have allowed a 

 low value of n but for gravel scattered throughout the ditch section, which had a great 

 influence on velocity, as the section is small. Coefficient n=0.0160. 



No. 38, Expt. S-37. This experiment is on the same lateral as No. 37 but covers a 

 straight reach immediately below the right-angle curve noted above. In the opinion 

 of the writer the value of n in this experiment is better for the gravel condition in a 

 small lined section than that found in the shorter reach used for No. 37. This gravel 

 ranged in size from fine to that of a walnut and had a marked influence in retarding the 

 velocity, as there was more or less movement of the gi-avel down the channel, which 

 retards velocity more than does stationary gravel. Coefficient 71=0.0192. 



No. 40, Expt. S-11, South Cottonwood Ward Canal, near Murray, Utah. This is a 

 lined stretch about 450 feet long between an earth section, and a wooden flume. There 

 is a slight curve at the upper end. A deposit of about 0.07 foot of fine sand and rootlike 

 growths covered the bottom and modified the original section of rather rough concrete. 

 A slight deposit of moss and slime also modified the sides of the channel. A reach 350 

 feet long was chosen in the middle of the lined stretch. Coefficient w=0.0171. 



No. 41, Expt. S-55, Modesto Irrigation District main canal, near Lagrange, Cal. As 

 shown in Plate III, figure 1, this reach of canal is on an approximate tangent. There 

 is a very sharp curve about 50 feet below the reach tested. The lining is a very good 

 grade of concrete, being about as rough as an orange. For the small amount of water 

 in the canal when tested the value of n is high, because of the presence of a number 

 of pieces of slate rock that have fallen into the canal from the adjoining cliffs. This 

 influence would probably be materially reduced when the canal is carrying water to 

 capacity. However, this experiment shows the value of cleaning the canal as often as 

 practicable in order to maintain a high carrying capacity which is much desired by 

 this district. Coefficient 7i=0.0174. 



No. 42, Expt. S-63, Santa Ana and Orange Canal, near Orange, Cal. In the reach 

 tested, 1,082.8 feet, there was a gentle curve between sta^tions 5 and 7. As shown in 

 Plate III, figure 2, which was photographed from a position about 200 feet below 

 station 10, this canal has the rough deposit and moss common to southern California 

 ditches. In addition the concrete lining of the bottom has been completely covered 

 by a deposit of soft sand from 0.1 to 0.2 foot deep. The caiTjdng capacity of such 

 ditches could be materially increased by the introduction of numerous sand gates of 

 some form. This lining had originally been a reasonably smooth piece of work, but 

 the deposits had destroyed much of the usefulness of the smooth concrete. Coefficient 

 n=0.0176. 



No. 43, Expt. S-70, Los Nietos Water Co.'s main canal, near Whittier, Cal. The sur- 

 face of the original lining in this canal is fairly smooth, but the deposit common to this 

 region has so changed its character that, aided by the roUing sand, a high value of n is 



