PNNL

Abstract

At The Dalles Dam on the Columbia River, fish are believed to sustain injury from exposure to turbulence and from collision with the dam baffle blocks and end sill at high spillway discharges in the stilling basin. Because taking velocity measurements would be exceedingly difficult in this environment, a system of pressure transducers was installed to record high-frequency pressure data during a range of spillway discharge scenarios. The transducers were mounted below Spillbays 4 and 9 on the top, face, and sides of baffles; the channel between baffles; and the top and face of the end sill. Results from three sensors below Spillbay 4 are presented. Statistical analyses show expected trends, such as mean pressure increasing during head-on flow, decreasing in flow separation zones, and being proportional to depth. Power spectra indicate increased low-frequency spectral power during heavy flows, typical spectral decay rates, and the existence of spectral peaks of possible hydraulic origin.