Integrating Drought Warning Water Level With Analytical Hedging for Reservoir Water Supply Operation

Abstract The increasing frequency of droughts worldwide, along with their substantial societal impacts, underscore the need for improved drought early warning and enhanced water supply security. While reservoir drought management strategies, including hedging theory and drought warning/limited water level (DWWL), have been extensively studied for their potential to alleviate water supply stress, effective control schemes remain lacking. This study proposes a framework to enhance reservoir drought resistance. The framework starts with the analytical derivation of the optimal hedging rule (HR) for reservoirs supplying multiple competing users, applicable to both real‐time and long‐term optimizations. DWWLs and their seasonal segmentation are then determined based on the optimal water supply process and multivariate time‐series clustering. By utilizing reservoir water level and meteorological drought indicator to monitor drought conditions and characterize reservoir effective storage, a real‐time operational strategy is ultimately proposed that integrates analytical HR with effective storage. We demonstrate the application in the Danjiangkou Reservoir in China, and the proposed operation is testified under both long‐term periods and extreme dry conditions. Results indicate that the analytical HR outperforms conventional rule curves in nearly every aspect, including water supply benefits, reliability, and refill rate. The DWWL proves crucial during extreme drought conditions; when water levels fall below DWWL, the HR considering DWWL restricts water supply earlier, thereby preventing the reservoir from dropping dramatically to critically low levels. This proposed framework is transferable to other water supply reservoirs, offering scientific support, operational relevance, and guidance for drought mitigation and response.