Influence of pumped-storage hydroelectric plant operation on a shallow polymictic lake: Predictions from 3-D hydrodynamic modeling

Abstract

Pumped-storage hydroelectric plants play important roles in electrical supply grids by providing electricity during periods of peak demand, storing renewable energy and controlling supply frequency. The pumping of water from a lower lake or reservoir to an upper impoundment and the return of that water during power generation can strongly affect the properties of pumped-storage reservoirs, however. For example, plant operation has been found to delay, weaken or eliminate thermal stratification, resuspend bottom sediments and entrain organisms. The aim of this study was to better understand the impacts of a proposed pumped-storage facility on stratification, mixing and sediment resuspension in Lake Elsinore, a shallow, polymictic lake in southern California. Three-dimensional hydrodynamic simulations were conducted using the Environmental Fluid Dynamics Code (EFDC). Model simulations demonstrated regular variations in the lake surface elevation of 0.24–0.5 m associated with pumping and generation, although a large shore-mounted intake structure resulted in quite low velocities near the intake (< 6 cm/s), bottom shear values below the assumed critical threshold for resuspension (< 0.1 N/m2), and limited overall effect on stratification and mixing in the lake. Entrainment of larval fish and other planktonic organisms remains a concern, however.