Figure 8. — Connector between haul-line and carriage. 



Figure 9. — Track and carriage at point of 

 stiff-leg attachment. 



Rate of Travel 



The velocity at which the screen should be 

 moved depends on the extent of impingement, 

 if any, and of accumulation of debris. Im- 

 pingement, should it occur, would require 

 screen travel at a rate suitable to carry the 





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n 



LJ 



SECTION 



Figure 10. — Corner joint of screen panel. 



fish into the bypass. Accumulation of debris 

 on the screen increases head loss and neces- 

 sitates rates of travel that provide for cleaning 

 of the screen. Because neither impingement 

 nor accumulation of debris was apparent at 

 Stanfield, the screen was usually moved at a 

 rate of only 40 cm.p.s. 



We have not determined whether the rate of 

 travel of the screen influences the degree of 

 head loss against the structure. 



Loss of Head 



Loss of head occurs because the screening 

 material forms a partial obstruction to the 

 flow. Structural members, such as the stiff- 

 legs, in addition to the debris, add to this 

 loss. To determine head loss at Stanfield, 

 water levels 1.2 m. upstream from the upper 

 end of the traveling screen and 1.2 m. down- 

 stream from its lower end were measured. 

 The difference between the two readings rep- 

 resented the head loss for the specific water 

 velocity at the time. At a mean velocity of 

 about 73.2 cm.p.s., with a nylon net of 12. 7-mm. 

 stretch nylon mesh (effective open area of 72 

 percent), the measurable head was only 

 9,14 mm. 



Efficiency of Deflection 



The traveling screen at Stanfield was in- 

 stalled early in June 1967 at the height of the 

 downstream migration of juvenile coho salmon. 

 We made a series of tests on the efficiency of 

 deflection of juvenile coho salmon and steel- 

 head trout in the canal. Water velocities varied 

 between 61 and 91.5 cm,p,s, (mean 73.2 

 cm.p.s.), whereas the depth fluctuated between 

 1.68 and 1.83 m. 



An inclined-screen trap placed at the down- 

 stream end of the bypass collected the fish 

 deflected by the screen (fig, 1), Fish not de- 

 flected by the screen were trapped in the bypass 

 of a drum-screen, a short distance downstream 

 from the traveling screen. 



12 



