Ecohydraulics of Fish Protection at Industrial Water Intakes

Developments to protect juvenile fish at industrial water intakes, such as those for oilsands projects on the Athabasca River in northern Alberta, provide practical design guidance.  Scale models demonstrate the importance of water intake geometry, flow guidance devices, and pump arrangements to achieve appropriate velocity magnitudes and distributions, as well as turbulence levels, for guiding and diverting fish effectively.  Furthermore, such hydraulic studies are important to ensure uninterrupted water supply, optimize intake operation, encourage self-scouring conditions riverside of the intake structure, and reduce maintenance from fine sediment accumulation, debris, and ice.  Fine sediment accumulations in intakes and frazil ice on fish screens have presented some operational challenges for water intake cleaning systems.  E-flow requirements (i.e. ecological, in-stream, or environmental flow regimes) may also affect water intake operations as they may limit river water withdrawals at low flow seasons (e.g. winter).  E-flow requirements may be established through simple desktop methods or sophisticated hydrodynamic and habitat modeling for ice-free and ice-covered conditions.  Meeting the operational challenges of E-flows, sediment and frazil ice may lead to increased off-river water storage to allow continuous industrial plant operation, while river water may be shut down for a few days (e.g. frazil ice) or weeks (E-flows).