THE FLOW OF WATER IN IRRIGATION CHANNELS. 29 
No. 25, Expt. S-19, North Side Twin Falls Land & Water Co.'s main canal near 
Milner, Idaho. As shown in Plate I, figure 3, this concrete lining fills out the main 
irregularities in a very rough lava-rock cut. An examination of the section below 
the water line was impossible at the time of making the experiment, and the various 
cross sections from which the value of R was deduced were taken from office notes. 
These covered bottom widths and elevations of the bottom at both sides and in the 
middle. A study of these notes shows that the bottom is undulating and that while 
the high velocity would prevent the accumulation of sand deposits, and lava rock 
does not slough off debris to any extent, yet the velocity is retarded by the disturb- 
ance in the filaments of current due to the undulations. Coefficient n=0.0138. 
No. 26, Expt. F-l, Davis and Weber Counties Canal, Utah. This experiment 
was conducted in the same canal as tests Nos. 28 and 29, but about 8 miles upstream 
and about 1 mile below the head gate from the river. Condition of bottom could not 
be determined, but was probably about the same as in No. 28. The concrete on 
sides was smooth and unbroken. The hydraulic grade was taken as the mean of five 
tests with level and piezometer and found to be 0.000413, while constructed grade of 
this portion of canal was 0.000445. Coefficient n =0.014. 
No. 27, McL., Davis and Weber Counties Canal, Utah. See Nos. 26-28-29. Coeffi- 
cient n=0.0144. 
No. 28, Expt. F-2. This experiment was on a reach 468.5 feet long, which was 
included in the reach 1,000 feet long described in No. 26. The hydraulic grade was 
taken as the mean of level lines run between 12 settings of the piezometer instrument 
spoken of under No. 14. The mean of these 12 observations gave a slope of 0.0006168, 
while the constructed grade of the canal, as stated by the chief engineer, was 0.000626, 
and in No. 29 the writer found the surface slope to be 0.000629. In the description of 
conditions B. P. Fleming states that the patches of gravel consisted of all sizes up to 
5 inches in greatest dimension and that probably 10 per cent of the area was covered 
with them, mostly adjoining the toes of the side slopes. This experiment was made 
about six weeks after No. 26. Coefficient n=0.0146. 
No. 29, Expt. S-13, Davis and Weber Counties Canal, Utah. This canal furnishes 
an example of the retarding effect of wooden expansion joints if they are not so set 
that they can not project into the canal section (PI. II, fig. 1). The lining was laid in 
slabs varying in width from 8 to 16 feet. Strips of wood a little larger than building 
lath were placed between the slabs with the idea that they would eventually be 
pulled and the space filled with asphalt. This has not been done, and at present 
the strips project from to 1£ inches into the section. However, the velocity at the 
bottom was retarded by small patches of gravel which have probably sloughed off the 
hillside cut in which the canal runs. This condition will probably be present each 
season, even though the canal be cleaned out once a year, but the friction factor n 
can undoubtedly be reduced one or two units in the third decimal place by carrying- 
out the original idea contemplated in the construction. Coefficient n=0.0154. 
No. 30, B-10, King Hill Canal, Idaho. This test was made on a reach covering 
both tangent and curves. The concrete was not surfaced, but left as hand tamped to 
grade. After surface coat had set, the 2 by 4 inch end forms were removed and the 
groove poured with a 1 to 1 mixture of sand and cement. The surface is described 
as quite rough, especially at the joints. The canal was clean of detritus and moss. 
Coefficient n=0.0143. 
No. 31, H-29, Hamilton flour mill flume, Montana. This flume was constructed 
recently of a 1 to 7 mixture of cement and sand with some fine gravel. The coat has 
a few blowholes, but is usually smooth. The concrete was deposited against wood 
forms and not plastered. The alignment is as follows: 10° curves at stations 4 and 6. 
Small curves at stations 8+50, 11, 14, and 20+50. The rest of the distance was on 
tangent (PL II, fig. 2). Coefficient n=0.0149. 
