Steeppass Fishway Development
barriers, channel, denil, entrainment, flow patterns, Gradient, model studies, salmon, slope, steeppass, streams, turbulence, upstream, water jet, water velocity
Informational Leaflet No. 12
Alaska Department of Fish and Game
A sectional, prefabricated, lightweight, corrosion resistant, functional steeppass fishway of the Denil type has been developed and successfully used for passing upstream migrating salmon over low head barriers. The average water velocity in relationship to the channel of the Model 'A' varies from two and eight-tenths to three and three-tenths feet per second at gradients between twenty and thirty-five percent. Flow patterns in the transit channel are complex and the rate of entrainment is high. The issuing water is attractive to the migrants and they have been observed to consistently enter the stream and fishway without hesitation. The fish in their transit appear to exploit the upstream directional components of motion of the re-entrant water jets which are introduced and directed to control the velocity of the water. Several test installations have been made to evaluate the steeppass under natural conditions and more are contemplated under steadily increasing heads and slopes to equate the uppermost limits of practical application against mathematically computed ceilings. Attempts to reduce the amount of air entrainment and water turbulence led to development of an alternate model (Model 'C') which has been tested hydraulically in full scale but not yet used in field installations. In this model, the average water velocity in relationship to the channel varies from four and one-tenth to four and five-tenths feet per second at gradients between twenty and thirty-five percent.