Quantifying hydropower flexibility during extreme temperature events

Kyongho Son, Cameron Bracken , Erfaneh Sharifi, Sohom Datta, Abhishek Somani

Extreme weather events can impose substantial stress on the electrical grid. Hydropower offers unique operational flexibility, enhancing grid resilience and reliability. Despite this value of flexibility, systematic assessments of hydropower flexibility -- particularly during extreme events -- remain limited. This study is the first to quantify hydropower operational flexibility using 25 years' observed hydropower generation data during cold snaps and heat waves, across ten federally operated reservoirs (the ``Big-10'') in the Pacific Northwest region of the United States. Among the Big-10, the Upper Columbia reservoirs—Grand Coulee (GCL) and Chief Joseph (CHJ)—have the largest storage capacities and exhibit the greatest operational flexibility, followed by the Lower Columbia and Lower Snake reservoirs. Flexibility is generally higher during cold snaps than during heat waves; however, the relationship between installed capacity and exercised flexibility is statistically significant only during cold snaps. Heat wave events, however, exert a more pronounced marginal impact on excess hydropower production, as indicated by the steeper slope of excess generation with respect to event severity. Overall, this study not only quantifies the system’s flexibility under extreme conditions but also enhances understanding of how individual reservoirs respond to temperature-driven stressors, providing valuable insights for grid management and future hydropower planning.