Author(s): Melina Sattelmeier; Anders G. Andersson; J. Gunnar I. Hellstrom; Staffan T. Lundstrom

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Keywords: Ecohydraulics; Hydraulic Modeling; Lake Ecosystem; Thermal Dynamics

Abstract: The increasing integration of fluctuating renewable energy into our energy systems has created a high demand for efficient electricity storage solutions, aiming to meet demand at intermittent supply conditions and maintain grid stability. Pumped hydropower storage (PHS) can be seen as a key solution, already accounting for the majority of the electricity storage today. However, the impact from PHS on reservoir ecology remains poorly explored, with open questions regarding how the physics within the reservoir is affected by pumping. Thermal stratification is a main factor influencing the ecological state of a lake ecosystem. To exemplify, stratification is a decisive factor for both nutrient recycling and deoxygenation. Therefore, this numerical study investigates the influence of PHS on thermal stratification in reservoirs. A 3D hydrodynamic model of a generic PHS reservoir is used to test how different types of stratification phenology are disrupted by a diurnal pumping cycle. The study demonstrates that thermocline phenology may influence the ecological effects of PHS operations by determining the extent of vertical mixing and thereby nutrient redistribution and oxygen availability. Scenarios with a well-established thermocline exhibit different responses to pumping compared to weakly stratified conditions, leading to variations in thermal structure and potential biological impacts. This adds to the comparability of existing case studies and, moreover, improves understanding of the thermal dynamics in hydropower reservoirs, necessary to optimize PHS operations as to the status of the ecosystem and enhance water quality management.

DOI: https://doi.org/10.64697/978-90-835589-7-4_41WC-P2037-cd

Year: 2025