Fish Ladders For John Day Dam, Columbia River, Oregon and Washington
Army Corps of Engineers, Columbia River, design, diffuser, entrance, fish counting, fish ladder, forebay, John Day Dam, model studies, orifices, salmon, shad, slope, sockeye salmon, turbulence, upstream, weir
Technical Report No. 103-1
U.S. Army Engineer Division, North Pacific
Facilities for passing fish upstream over John Day Dam include a powerhouse collection system with fishway entrances at each end and along the downstream face of the powerhouse, and a 24-ft-wide fish ladder with 1-on-10 slope on both sides of the river. The north fish ladder (except entrance section) and a portion of ladder adjacent to the south fish counting station were studied in a 1:10-scale model. A group of four typical diffusion chambers in each ladder was reproduced in a 1:8-scale model. Fishway weirs with 6-ft-long overflow crests at each end of a 12-ft-long nonoverflow section, upstream fins, and 18- by 18-in. orifices at the floor were adopted. Orifice sizes in the regulating sections were adjusted to control discharge and head drops between 19 nonoverflow bulkheads for an 11-ft range in forebay levels. Sloping floors, baffle beams at a constant elevation, and metering orifices sized to provide 60 cfs each were selected for diffusers in sloping portions of the fish ladders. Improved designs were developed for the bulkhead and weir adjacent to the north fish counting station. The addition of a third orifice in bulkheads of the regulating section (to assist passage of shad and sockeye salmon) increased turbulence at the north fish counting station. The south fish counting station, with an illuminated vertical counting board, was satisfactory after the orifices in the adjacent downstream weir were enlarged to reduce head on the weir.