The Role of Water Demand and Paleo Streamflow in Advancing Reservoir Drought Risk Analysis

Abstract Effective water demand management is critical for adaptation during drought periods. However, drought planning is challenged by the lack of rigorous water demand‐integrated measures and the limited number of drought event samples based on instrumental data. We propose a Normalized Reservoir Drought Index (NRDI) and associated drought event metrics that can inform reservoir operations. Using NRDI, we analyzed the effectiveness of demand management and paleo streamflow data in assessing drought risks—the exposure related to meeting water demands during certain drought events. We explored reservoir drought risk analysis using data from seven reservoirs in the western United States. The NRDI was derived from inflow and estimated water demand and subsequently compared to observed reservoir storage. The NRDI and event metrics demonstrated responsiveness to observed storage. Comparative analysis of drought risk using paleo and instrumental inflow highlighted the importance of paleo inflow, providing larger drought event samples and broader extreme ranges. Sensitivity of drought risks was quantified under varying demand conditions. As expected, the sensitivity was more significant in extreme events than moderate events. This paper provides an effective and robust measure for reservoir managers to manage water releases during drought periods and a valuable tool to assess reservoir risk to drought by considering natural variability more broadly, and providing a deeper understanding on the sensitivity of drought risk to demand alterations.