THE FLOW OF WATER IK WOOD-STAVE PIPE. 61 



The type of construction with a well having a rounded intake is 

 shown in C, Plate IX. This type is generally used where the hillside 

 is very steep just at the pipe intake or where a drop in grade line is 

 included in the well structure. 



In D, Plate IX, is shown a type of entrance structure for both 

 round and square pipes quite frequently used by the United States 

 Reclamation Service where moderate velocities (5 or 6 feet per sec- 

 ond) only are to be considered. 



The west Okanogan irrigation district (Washington) uses a general 

 type like E, Plate IX, for both inlet and outlet structures. In the 

 inlet structure shown the concrete rounds into the pipe opening, the 

 center of which is level with the bottom of the canal. 



The forms, reinforcement, and final entrance of a large siphon in 

 Wyoming are shown in Plate XIII. 



A pipe with both inlet and outlet tapering, such as condition 3, 

 will have the maximum efficiency as it approaches a "Venturi tube 

 with elongated throat," as described to the writer by D. C. Henny. 

 Such a structure would have the sides of the inlet converge at the 

 rate of about 1 in 5, while the transition section at the outlet would 

 diverge at the rate of about 1 in 24. On such a pipe less than 5 per 

 cent of the velocity head will be unrecovered, charging all losses 

 other than friction to entry head. 



The transition section usually includes part of the intake or out- 

 let structure proper and also a short length of the wood pipe. On 

 the Arkansas Valley conduit of the Colorado Fuel & Iron Co. there 

 are 25 siphons of wood, incased in concrete.^ The intake ends of 

 these siphons taper at the rate of 1 inch per foot of pipe until the 

 diameter at the opening is 1 foot greater than that of the main pipe* 

 The inlet to one of these siphons is shown in figure 3, Plate XII. 



This argument regarding conservation of velocity head and reduc- 

 tion of entry head is exemplified in the recently completed designs 

 for a large siphon carrying water at a very high velocity at the Sun 

 River crossing on the Sun River project of the United States Recla- 

 mation Service. The outlet structure is shown as A in Plate IX. 



The water section in the leading canal has an area of 928 square feet 

 with a velocity of 1.08 feet per second. By tapering wing walls and 

 concrete intake structure the area at the upper end of the wood-stave 

 pipe has been reduced to 50.3 square feet (96-inch pipe) and the 

 velocity increased to 19.9 feet per second. By this time 6.14 feet of 

 head of elevation has been devoted to. building up a high velocity. 

 Of course it is important that as much as possible of this velocity 

 head be recovered at the outlet end. 



1 Frictional Resistance in Artificial Waterways. V. M. Cone, R. E, Trimble, and P. S. Jones, Colorado 

 Sta. Bui. 194 (1914), 



