trees, and twigs into the flume above the 

 screen. When the travel rate of the screen 

 was equal to the velocity of the water, the 

 debris was not forced into the meshes. As the 

 screen turned away from the entrance to the 

 bypass, material that had contacted the screen 

 separated from it and entered the bypass. 



Even though the two systems operated ef- 

 ficiently, we recognize that modifications in 

 design will be required in a prototype facility. 



ADVANTAGES OF THE SCREEN 



On the basis of 2 years of operating the 

 Carson Hatchery flume, we believe the travel- 

 ing screen has certain advantages: 



1. Operational efficiency of the facility 

 remains high irrespective of fluctuations in 

 depth of the water. 



2. Higher allowable approach velocities are 

 possible--if the fish were forced against the 

 screen, they would be carried to the bypass 

 and released. 



3. Operational wear is potentially less than 

 in industrial water screens, because all travel- 

 ing units for support of the screen are above 

 water. 



4. The traveling screen is self-cleaning. 



5. Loss of head is small in model II--only 

 single screening is involved in contrast to 

 double screening for the drunn and industrial 

 water screens. 



The rate at which the screen moves depends 

 on the amount of impingement, if any, and 



debris load. The rate must be adjusted so that 

 small fish swept against the screen by the 

 current will be carried into the bypass and 

 released. Heavy debris loads could create 

 loss of head and require faster travel to keep 

 the screen clean. 



In other systems, the juvenile migrants are 

 either injured when dashed against drunn 

 screens and industrial water screens, or lost 

 when swept through louvers. Migrants are not 

 aided in reaching a bypass. Therefore, screens 

 of existing systenns require considerable at- 

 tention during periods of turbulence and high 

 velocity. In contrast, such conditions are of 

 far less consequence whenthe traveling screen 

 is used because the fish swept onto the screen 

 are carried to the bypass and released. 



This research has provided a basis for 

 several new traveling screens whichare either 

 in the design stage or under construction. 

 Engineering improvements have provided the 

 cable-suspension systems to reduce installa- 

 tion costs, cantilevered stiff-legs to counter 

 water pressure, relatively inexpensive but 

 durable nylon netting, and more efficient 

 track, carriage, and power-drive systems. 



LITERATURE CITED 



BRETT, J. R., and D. F. ALDERDICE. 



1958. Research on guiding young salmon at 

 two British Columbia field stations. 

 Fish. Res. Bd. Can., Bull. 117, 75 pp. 



MS. # 1846 



