Fate of reservoir storages due to sedimentation in changing climate

Retention of sediment in lakes and reservoirs is a major problem that impacts drinking water supplies, irrigation, recreation, hydropower production, and flood control globally. Sediment loads to lakes and reservoirs are likely to increase due to changing climate, e.g. increases in high intensity precipitation events. However, this impact is often not considered in large scale hydrological assessments of climate changes.An ongoing challenge with assessing reservoir sedimentation at a large scale is that many basins are ungauged, and information about sediment management and decision making is not available. Large-scale dynamic hydrological models are fortunately becoming more commonly established as tools not only for flood forecasting and climate impact analyses, but also for estimating time-dynamic water fluxes and their transport into sea basins. One such tool is the dynamic, semi-distributed, process-based rainfall-runoff and water quality model, Hydrological Predictions for Environment (HYPE, see Lindstrm et al., 2010; https://hypeweb.smhi.se/).While many hydrological models do not explicitly consider the sediments accumulating in reservoirs, HYPE was recently updated to dynamically simulate (1) the effect of sediments on the available volume of lakes and reservoirs and (2) selected sediment management strategies. The new routines were tested on several reservoirs globally using different types of data for calibration: instream sediment concentrations (Banja in Albania), storage capacity loss (Enguri in Georgia), and upstream sediment yield (dams in Greater uMngeni River Basin in South Africa). The current annual rate of storage capacity loss varied greatly among cases (0.004-4.15%). The routines were then incorporated into a pan-European HYPE model, E-HYPE (Brendel et al., 2023), and calibrated against observed sediment concentrations. The change in storage capacity loss in European reservoirs and lakes was then evaluated for 3 climate models. We present current and future losses of lake and reservoir storage and analyze sediment regimes in water bodies with water management structures such as hydropower or drinking water reservoirs.Lindstrm, G., Pers, C., Rosberg, J., Strmqvist, J., Arheimer, B., 2010. Development and testing of the HYPE (Hydrological Predictions for the Environment) water quality model for different spatial scales. Hydrol. Res. 41, 295319. https://doi.org/10.2166/nh.2010.007Brendel, C. E., Capell, R., Bartosova, A. (2023) To tame a land: Limiting factors in model performance for the multi-objective calibration of a pan-European, semi-distributed hydrological model for discharge and sediments. Journal of Hydrology: Regional Studies, 50(2023) 101544. https://doi.org/10.1016/j.ejrh.2023.101544