Adapting reservoir operation to climate change in regions with long-term hydrologic persistence

Large-scale climate variability patterns such as El Nino-Southern Oscillation (ENSO) influence the hydrology and hence affect the management of water resources in numerous regions around the globe. The presence of multiyear drought and wet periods is already challenging as these long, extreme, events tend to stress water resources systems much more than multiple, isolated, ones. This manuscript presents a variant of a hydrologically-driven approach to assess the performance of large-scale water resources systems in regions where the long-term persistence that characterizes the flow regime is likely to be affected by climate change. This approach comprises several steps including the construction of a large ensemble of hydrological projections which are biascorrected in the frequency domain to account for the long-term persistence; the clustering of these projections based on hydrologic attributes to identify likely alterations of the flow regime; and the use of an optimization model to derive allocation policies tailored to identified alterations of the flow regime. The proposed approach is tested on the Senegal River basin which has experienced multiyear dry, normal, and wet periods in the past. The analysis of allocation policies highlights the relevance of climate-tailored policies in adapting to climate change, with climate tailored policies yielding moderate gains under the most extreme alterations, while they remain meaningful under more moderate ones.