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Hydropower operations optimization subject to environmental constraints is limited by challenges associated with dimensionality and spatial and temporal resolution. The need for high-fidelity hydrodynamic and water quality models within optimization schemes is driven by improved computational capabilities, increased requirements to meet specific points of compliance with greater resolution, and the need to optimize operations of not just single reservoirs but systems of reservoirs. This study describes an important advancement for computing hourly power generation schemes for a hydropower reservoir using high-fidelity models, surrogate modeling techniques, and optimization methods. The predictive power of the high-fidelity hydrodynamic and water quality model CE-QUAL-W2 is successfully emulated by an artificial neural network, then integrated into a genetic algorithm optimization approach to maximize hydropower generation subject to constraints on dam operations and water quality. This methodology is applied to a multipurpose reservoir near Nashville, Tennessee, USA. The model successfully reproduced high-fidelity reservoir information while enabling 6.8% and 6.6% increases in hydropower production value relative to actual operations for dissolved oxygen (DO) limits of 5 and 6 mg/L, respectively, while witnessing an expected decrease in power generation at more restrictive DO constraints. Exploration of simultaneous temperature and DO constraints revealed capability to address multiple water quality constraints at specified locations. The reduced computational requirements of the new modeling approach demonstrated an ability to provide decision support for reservoir operations scheduling while maintaining high-fidelity hydrodynamic and water quality information as part of the optimization decision support routines.

Plain Language Summary Hydropower operations can influence water quality, including temperature and dissolved oxygen (DO) concentrations both upstream and downstream of dams. Meanwhile, as energy demands increase it is important to improve the efficiency and capacity of renewable sources. A well-optimized hydropower system thus requires a fully integrated approach where environmental quality and energy production are achieved together. Currently, hydropower optimization subject to environmental constraints is limited by dimensionality, resolution, and computational expense of detailed hydrodynamic and water quality models. The need for integrating these models within optimization schemes is now driven by improved computational capabilities, requirements to meet specific points of compliance, and the need to optimize systems of reservoirs. This study describes an approach for computing hourly power generation schemes for a hydropower reservoir using high-fidelity models, surrogate modeling techniques, and optimization methods. Surrogate models, which emulate the predictions of complex models at much less computational expense, are integrated into an optimization routine that maximizes hydropower generation subject to dam operations and water quality constraints. For the case study, the method found potential increases in hydropower production value relative to actual operations while maintaining DO minimum concentrations, and produced an expected decrease in power generation at more restrictive DO limits.