Roles of reservoirs in regulating basin flood and droughts risks under climate change: Historical assessment and future projection

Abstract

Study regionNenjiang River Basin (NRB), Northeast China. Study focusWater safety management and sustainable development planning increasingly seek to incorporate the impact of reservoirs on downstream floods and droughts; while the effectiveness of reservoir operation in regulating flood and drought risks under climate change has not been assessed extensively. We focus on discerning whether and to what extent reservoirs can mitigate the risk of hydrologic extremes from the perspective of historical and future climate change. New hydrological insight for the regionWe found that coupling reservoir operations into basin hydrological simulation can efficiently improve model capacity to capture both flood and hydrological drought characteristics. The Nierji Reservoir contributed largely to reducing historical flood and drought risks in the NRB. However, the risk of floods and hydrological droughts will increase under future climate change, and reservoir operations cannot completely eliminate the increasing risks of future floods and hydrological droughts. The annual probability of flooding under different future scenarios will exceed 48%, much higher than the 22.2% for the historical period. The frequency of droughts is anticipated to increase by 139.20% under the Shared Socioeconomic Pathways (SSP) 370 scenario. To mitigate the increase of flood and drought risks caused by future climate change, it is necessary to further optimize reservoir scheduling principles, thereby improving the basin's resilience to hydrological extremes.