Table 1. — Percentage deflection of coho salmon and steelhead trout by traveling screen of 12.7-nim. 

 stretch nylon mesh placed at an angle of 20° with the water flow In Stanfield Canal, 1967 



Date 



June 



Water 

 temperature 



■'c. 



Water 

 velocity 

 in the 

 canal 



Water velocity 

 in the bypass 



compared 

 with velocity 

 in the canal 



Cm. /sec. 



Test fish 



Coho salmon 



Fish 

 used 



Fish 

 deflected 



Steelhead trout 



Fish 

 used 



Percent 



Number 



Percent 



Number 



Fish 

 deflected 



Percent 



The curtain of continuously moving netting 

 (12.7-mm. stretch nylon) deflected 97 to 100 

 percent of the young steelhead trout and coho 

 salmon (table 1), Fish that were not deflected 

 by the screen probably passed under the net 

 near the point where it entered the water. 

 This area was difficult to seal. In models VI 

 and VII the screens will not be raised out of 

 the water, and this problem will be eliminated. 



Self-Cleaning Capabilities 



The Stanfield screen represents the fifth 

 experimental screen model;' common to all 

 models is the capacity for self cleaning. This 

 action results from a reverse flow through the 

 net at the entrance to the bypass. Such a flow 

 can be developed in different ways, depending 

 on the design of each traveling screen. As yet, 

 no supplementary cleaning system has been 

 needed. 



To prevent damage to the net by large pieces 

 of debris, such as logs, a conventional trash- 

 rack was installed within the Stanfield Canal 

 just upstream from the traveling screen. The 

 rack was constructed of 5.08- by 7.62-cm. 

 metal tubes, spaced on 20.32-cm. centers. 



'Each of the previous models, I through IV, represents 

 In succession an advanced and Improved design. Model VI, 

 recently installed in the Troy, Oreg., test flume and 

 capable of screening over 28c.m.s. of water, has many de- 

 sign improvements such as a completely horizontal track 

 (eliminating the screen lift-out feature), readily removable 

 panels, and panels that open up on their return travel to 

 reduce head loss. We will make additional design im- 

 provements in model VII, now being designed for the 

 Leaburg Canal, Eugene, Oreg. 



Handling large debris, such as logs, will be 

 more difficult in situations that may require 

 screening of large volumes of water--30 

 c.m.s. or more. In recognitionof this problem, 

 we developed and tested a traveling debris net 

 at another test site.* The tests indicated that 

 logs 6 m. long and 1 m. in diameter (with 

 limbs attached and weighing over 1,000 kg.) 

 could, after being swept onto the cable-formed 

 screen, be carried easily and rapidly into a 

 quiet pond for removal by conveyor. 



Bypass 



Whatever the success in fish deflection by 

 any screen, it could be readily nullified by 

 inefficient bypass operation. To secure satis- 

 factory results, two basic factors must be 

 considered: The first involves adequacy of 

 bypass width. To ensure fish acceptance of the 

 model V bypass, the width was set at 0.61 m, 

 which is generally considered by biologists 

 (Ruggles, 1964) to be the maximum required. 



The second bypass factor concerns the 

 velocity relation of the bypass flow to the 

 main canal flow. A bypass velocity of about 

 140 percent of the approach velocity is sug- 

 gested (Bates and Vinsonhaler, 1957). Any re- 

 duction of velocity within the bypass causes 

 the fish to either hesitate or refuse the bypass 

 connpletely. 



* Bates, D. W., E. W. Murphey, andM. J. Beam. Travel- 

 ing net for removal of water-borne debris from rivers. 

 U.S. Fish Wlldl. Serv., Bur. Commer. Fish. Biol. Lab., 

 Seattle, Wash. [Manuscript,] 



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