Author(s): Dilip Mathur; Paul G. Heisey; John R. Skalski; Steven G. Hays; Mark R. Smith
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Abstract: Spillways and sluiceways at hydroelectric dams were constructed strictly as conduits for transporting excess river flow or debris with little focus on potential for safe fish passage. However, the declining salmonid populations have helped emphasize a critical re-examination of spillways and sluiceways as effective fish passage routes. Consequently, spillways at some hydro dams have been modified either to take advantage of surface oriented behavioral patterns to bypass fish via installation of prototype overflow weirs or installed with flow deflectors to reduce total dissolved ga levels in the river. These spillway modifications have opened up a new set of fish passage survival issues. Controlled tag-recapture experiments at hydroelectric dams on the Columbia River show that not all spillway structural modifications are 100% fish friendly; differences in survival at unmodified spillbays between sites also occurred. Estimated survival of juvenile chinook salmon in spillway passage ranged from 95.5 to 100%. It appears that depth of the tainter gate opening, amount of gate opening, discharge volume, obstructions in flow path (e.g., dentates, end walls), excessive turbulence, presence of boulders, etc. may affect fish survival. Hydraulic modeling and detailed physical examination of spillways, in combination with fish survival information, may open new opportunities and economic impetus to incorporate appropriate structural modifications that afford safer fish passage at spillways.
Year: 1997