Modeling hydropower operations at the scale of a power grid: a demand-based approach

Abstract. Climate change and evolving water management practices may have a significant impact on hydropower generation. While hydrological models have been widely used to assess these effects, they often present some limitations. A major challenge lies in modeling the release decisions for hydropower reservoirs, which result from intricate trade-offs, involving power sector dispatch, competing water uses, and the spatial allocation of power generation within the grid. To address this gap, this study introduces a novel demand-based approach for integrating hydropower within the routing module of land surface models. First, hydropower infrastructures are located in coherence with the hydrological network, and links are built between hydropower plants and their supplying reservoirs to explicitly represent water transfers built for hydropower generation. Then, coordinated dam operation is simulated by distributing a prescribed electric demand to be satisfied by hydropower across the different power plants within the power grid, while considering the operational constraints associated with the multipurpose nature of most dams. To validate this approach, we implement the framework within the water transport scheme of a land surface model and assess it with the case study of the French electrical system. We drive the model with a high-resolution atmospheric reanalysis and prescribe the observed national hydropower production as the total power demand to be met by hydropower infrastructures. By comparing the simulated evolution of reservoir stocks to observations, we find that the model simulates realistic operations of reservoirs and successfully satisfies hydropower production demands over the entire period. We also highlight the roles of uncertainties in estimated precipitation and of the limited knowledge of hydropower infrastructure in the estimation of production. Finally, we show that such an integration of hydropower operations in the model improves the simulations of river discharges in mountainous catchments affected by hydropower.