Abstract

Climate change will have significant impacts on Pacific Northwest hydrology. For water and environmental resource managers, an improved understanding of climate impacts at the watershed scale is critical for regional mitigation and adaptation. The Pacific Northwest's Green River Basin is a valuab... Show moreClimate change will have significant impacts on Pacific Northwest hydrology. For water and environmental resource managers, an improved understanding of climate impacts at the watershed scale is critical for regional mitigation and adaptation. The Pacific Northwest's Green River Basin is a valuable water supply, major flood risk, and provides habitat to cold-water aquatic species. Streamflow in the basin is seasonally regulated for flood prevention and flow modulation for ecosystem health. This study investigates the implications of climate change on streamflow and snowpack in the Green River Basin. Climate sensitivity analysis and future climate change impacts are simulated using the Snow17/Sacramento Soil Moisture Accounting model (Snow17/Sac) implemented with two elevation zones. Future climate change impacts on basin hydrology are assessed using an ensemble of statistically downscaled climate projections from Global Climate Models (GCMs) run as part of the Intergovernmental Program on Climate Change 5th Assessment Report. The application of two future emission scenarios (RCP 4.5 and 8.5) lead to moderate increases in streamflow volume and 49.9% to 84.0% reductions in snowpack by the year 2079 for RCP 4.5 and RCP 8.5, respectively. Center timing of streamflow is projected to shift towards earlier timing indicating that the basin is predicted to evolve from a transient to rain-dominated watershed. This shift in the annual hydrologic cycle could lead to heightened demands on seasonal water needs and changes in the frequency of extremes (flood and drought). Future planning and reassessment of how water is managed in the Green River Basin may be necessary to maintain operations that suffice to meet the region's water needs. Show less