596 



U. S. BUREAU OF FISHERIES 



check of fish left stranded in the system in the fall of the year, 

 to«!;ether witli obsei-vations made diirin<!; tlie iiTi<»:ation season. lead to 

 the conclusion that this sci-een lias effected the saving of a good 

 percentage of fish passing down river, and its use is held to be 

 justified. 



Wapaito electric screen. — Tlie Wapato Canal of the U.S. Indian 

 Irrigation Service diverts water from the Yakima River about 3.5 

 miles upstream from Sunnyside Dam. Capacity of the canal is 

 1,800 second-feet. The 1930 diversion period extended from March 

 11 to November 22. For the major part of the irrigation season the 

 amount of the diversion was close to the capacity of the ditch. 



The screen employed here during the 1930 season was the same as 

 described in the 1929 report. Although a good amount of water 

 overflows the Wapato Dam at all times the depth of flow on the 



Fkjukk 0. — New electric screen at Wapat" intake. See Fi.mire 0, Fislieries docu- 

 ment No. 109(), for a view of earlier installation 



ci'est of the dam is shallow. On the other hand, the intake gates 

 lift off the floor of the intake where the depth of water is approxi- 

 mately 20 feet, making the suction very great. This fact, coupled 

 Avith the very high water velocities existing along the line of the elec- 

 tric screen, created a situation quite unfavorable to the successful by- 

 passing of fish diverted by the screen. 



To overcome, as much as possible, these undesirable conditions, 

 the new screen planned for 1931 will be supported farther out in the 

 forebay where Avater velocities are lower ancl will be of the improved 

 insulated type with large electrodes energized with GO-cycle alter- 

 nating current from a transformer. 



A comprehensive check on the fish left stranded in tlie Wapato 

 system was made at the end of the irrigation season, and additional 

 information on this subject was secured when the principal laterals 

 were dried up for cleaning in midsummer. Consideration of these 

 findings and observations as to the presence of fish both in the river 

 and in the ditch system indicates that in spite of the poor by-pass 

 facilities and the unfavorably high velocities prevailing at the in- 



