The Western U.S. relies heavily on water-dependent electricity generation, with hydropower and fresh surface water dependent thermo-electric plants accounting for over 60% of generating capacity. These plants benefit enormously from the region’s snow-melt dominated hydrology, which provides additional storage and augmented flows throughout the summer. Yet long term power system planning often overlooks possible long-term changes to regional hydrology, instead focusing on acute changes such as policy and new technologies.

First, leveraging a multi sectoral multi scale modeling framework, we present an economic analysis of the sensitivity of current Western U.S power system operations to future water availability and how it impacts regional import/export dynamics. The power system expansion plans for resource adequacy purposes are most often developed at the regional scale, while they are further evaluated at the grid scale. Thus in a second part we also assess power shortfall risk for the U.S. Pacific Northwest under combined climate impacts on loads and hydropower generation. Our results indicate climate change could cause a seasonal shift in shortfall risk. We isolate individual contributions of changes in load and water availability in this seasonal shift and demonstrate the impact of representing the combination of the stresses. Finally we discuss geophysical research directions toward translating slowly changing water availability and load projections into associated risk-based acute multi scale changes, e.g. shocks with a timeline, in order to integrate with energy sector long term planning and inform progressive adaptation measures.