WATERFLOW 



I 



6.4 M.-Y^ 



TRAP 



FiouEE 6. — Electrode array with spacing of electrodes as indicated. 



trode array would not overlap and prevent the 

 entry of fish. Observations indicated that the elec- 

 trical field did not affect fish swimming more than 

 0.9 to 1.2 m. away from the electrodes; hence, any 

 fish migrating in an area about 4.0, m. wide in the 

 middle of the canal were able to enter the array 

 trap without being visibly affected by the electrical 

 energy. 



The trap entrance occupied 34 percent of the 

 cross-sectional area of the canal. Measurements 

 showed that when the water velocity in the canal 

 was 0.2 m.p.s., the trap screened about 33 percent 

 of the flow. At higher water velocities the hydraulic 

 head on the trap lead-in screens increased and 

 some water tended to flow upstream aroimd the 

 end of the screens rather than through them. Con- 

 sequently, the trap screened only about 29 percent 

 of the flow at a water velocity of 0.5 m.p.s. and 

 about 25 percent at 0.8 m.p.s. 



The trap lead-ins, converging at a 30° angle 



(fig. 10) extended downstream from the trap en- 

 trance to the trap throat. Each of these lead-ins 

 was 11.6 m. long and consisted of 11 screens of the 

 same design and construction as those used in the 

 velocity control structure at the entrance to the 

 water-diversion channel. An ovei-head lifting de- 

 vice facilitated the cleaning of the screens. The 

 trap throat was 0.5 m. wide by 2.4 m. deep. It was 

 equipped with guides to accommodate a gate that 

 could be closed when the trap was being emptied. 

 The trap holding area was about 3 m. wide, 3 m. 

 long, and 2.4 m. deep. It was equipped with a metal 

 brail that was divided into four sections by wooden 

 separators (fig. 11) to facilitate the removal of 

 captured fish. The brail was lifted by a wire rope 

 attached to an electric winch. 



EVALUATION FACILITIES 



Facilities for evaluating the fish-guiding effi- 

 ciency of the electrical system were about 150 m. 



FISH-GUIDING EFFICIENCY OF AN ELECTRICAL GUIDING SYSTEM 



318 



