THE FLOW OF WATER IN IRRIGATION CHANNELS. 29 



No. 25, Expt. S-19, North Side Twin Falls Land & Water Co.'s main canal near 

 Jklilner, 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 7i=0.0138. 



No. 26, Expt. F-1, 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 IJ 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 Ilill Canal, Idaho. This test was made on a reach covering 

 both tangent and curves. The concrete was not surfaced, but left as hand tam])ed to 

 grade. After surface coat had set, the 2 by 4 inch end forms were removed and the 

 grorjve poured with a 1 to 1 mixture of sand and cement. The surface is described 

 as quite rough, osper-ially at the joints. The canal was clean of detritus and moss. 

 Coefficif^t 71=0.0143. 



No. 3J, 11-29, IJamilt/)n fl'jur mill flume, Montana. This flume was constructed 

 recently of a 1 to 7 mixture of cfinent and sand with some fine gravel. The coat has 

 a few blowhoIe.H, hnt in UHiiaily smfjoth. The concrete was dejMwited against wood 

 form.H and n<it pla.stered. The aiigninent is as follows: 10° ciirvcH at Htafions 4 and 6. 

 Small ciirvoH at Htationw 8+.')0, II, 14, and 20+50. The rest of iht- dLslanf-e was on 

 tangent (PI. II, fig. 2). Coefficient n=0.0149. 



