30 BULLETIN 194, U. S. DEPARTMENT OF AGRICULTURE. 
No. 35, Expt. S-69, Sanderfer Ditch Co.'s main canal, near Whittier, 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 goodj 
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, 
so the added expense of the former does not appear to be warranted in view of the j 
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 
34 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 gravel down the channel, which 
retards velocity more than does stationary gravel. Coefficient n= 0.0192. 
No. 40, Expt. S-ll, 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 n=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 n=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 stations 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 carrying 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 rolling sand, a high value of n is 
fsm 
