78 BULLETIN 376, U. S. DEPARTMENT OF AGRICULTURE. 



tlie line. Henny states ^ that too much reliance should not be placed on this testae 

 " the only method at hand to determine the flow was from frequent determination of 

 velocity by means of vertical floa,ts in a semicircidar flume at the upper end of the 

 pipe. ' ' This test was not used by Williams-Hazen, Moritz, or the writer in the deriva- 

 tion of their formulas. The friction factor found indicates a capacity greater than the 

 average. According to Henny's report in the Reclamation Record for August, 1915, 

 this pipe is still sound ' ' except some deterioration where covered with loose rock only. " 



No. 33. Rectangular Un planed Poplar Pipe. — Tests on an experimental pipe 

 2.624 feet wide and 1.64 feet deep were made in France by Darcy and Bazin. As the 

 pipe is similar to that described as No. 22 the same discussion applies to both. (See 

 page 76.) 



No. 35. 31-incli Continuous-Stave Douglas Fir Siphon Pipe, Prosser Pipe 

 Line, Sunnyside Project, U. S. Reclamation Service, Washington. — In the 

 discussion of the Moritz tests J. S. Moore gives the details of experiments conducted 

 by him on the Prosser pressure pipe. Irrigation water is conveyed across the Yakima 

 Valley over the Yakima River in a pressure pipe of combination type. A concrete 

 pipe 30J inches in diameter is used until the head reaches about 45 feet, at which 

 point the line is changed to a 31-inch stave pipe. The reach tested has but one 5- 

 degree curve, for about 19 degrees of central angle, located near the outlet end. At 

 the river the maximmn head is about 105 feet. The tests were conducted in August 

 and October of the first irrigation season after the pipe was finished, the highest 

 velocity being obtained only in August. Before backfilling, but following recinching 

 of bands, external diameters were measured every 50 feet. The discharge was ob- 

 tained from the rating curve of a 6-foot Cipolletti weir, the curve having been ob- 

 tained by calibrating the weir against current-meter measurements from a meter sta- 

 tion near the weir. The capacity of this pipe was about 6 per cent less than the dia- 

 charge computed by the new formula. From the fact that the feed canal is down a 

 very steep grade in a natural channel for part of the distance it appears to the writer 

 that the pipe might very easily contain suflicient debris to account for any deficiency 

 in capacity. 



No. 36. — This is another reach of the same pipe as that last described. These 

 tests covered a shorter piece, included in the long reach tested as No. 35. The two 

 runs made at the highest velocity, in August, showed the same loss of head per unit of 

 length in both reaches of pipe, but the other runs, made in October, gave divergent 

 results, as shown on Plate VI. Mr. Moore states that he is not prepared to explain 

 this divergence. This series of testa indicate that the capacity is 10 per cent less than 

 the discharge computed by the new formula. (See discussion of No. 35.) 



No. 41. 44:J-inch Continuous- Stave Douglas Fir Pipe, Municipal Water 

 Supply, Seattle, Wash.^ — T. A. Noble conducted a series of tests on a 44-inch pipe 

 at the time the tests on the 54-inch pipe (discussed as No. 44, p. 79) were carried on. 

 With the exceptions noted below the same general methods were used on both pipes. 

 The horizontal curves in the 44-inch pipe were so flat that for all practical purposes 

 the pipe may be considered straight. For about one half the total reach the pipe 

 follows an even gradient. For the other half it crosses a depression about 10 feet in 

 maximum depth in a distance of about 2,000 feet. Thus, practically, the pipe is with- 

 out curvature in either plane. After passing through the reach of 54-inch pipe dis- 

 cussed as No. 44 the water enters a settling basin. From this basin it is conveyed in 

 the 44-inch pipe now under discussion. Water columns were used for both gauges. 

 Gauge No. 1 was located 150.6 feet downstream from the inside wall of the basin. 

 Gauge No. 2 was located 4,041 feet farther down the pipe line. No growth appeared 

 witliin the 44-inch pipe; according to Noble the higher velocities in the 44-inch pipe 



1 Journal Assoc. Engin. Socs., 21 (1898), p. 250. 



2 Trans. Amer. Soc. Civ. Engin., 49 (1902), p. 113. 



