Resilience Scanner

Watershed-Specific Downscaled Climate Projection Modeling

Solution Overview

Seattle's water utilities collaborated with federal and academic research institutions to develop downscaled climate projections specifically tailored to the watersheds supplying the city's water.[5] This approach enables the utilities to translate global climate models into actionable, watershed-specific data that informs water supply planning and climate adaptation strategies.[1][2] The initiative addresses critical uncertainties about how climate change will affect water availability, forest fire intensity, turbidity, and precipitation patterns in the region.[5]

Technical Components

Seattle City Light worked with the University of Washington Climate Impacts Group to develop climate change projections for the region based on the latest climate models and greenhouse gas emissions scenarios from the Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment Report.[1] The climate change impact evaluation incorporated multiple climate models at every stage of the process and used the values produced to generate an ensemble average that quantifies the most likely impact, with the ensemble average characterized by an envelope of uncertainty based on the range and spread of the individual GCM ensemble members.[2] The PUMA project applied results from the climate model evaluation study and used downscaled climate data from the MACA dataset.[3] Seattle Public Utilities ran eight of a planned 40 regional climate change simulations created by downscaling global computer models that plot the likely trajectory of climate change.[4]

Implementation Details

Seattle City Light developed its Climate Change Adaptation Plan in collaboration with the University of Washington Climate Impacts Group, which provided state-of-the-science climate change projections for the Pacific Northwest and technical assistance in conducting the vulnerability assessment.[1] Seattle Public Utilities partnered with CIRC to understand how climate changes—from a loss of snow to wildfires—might affect their ability to provide water to their customers.[3] CIRC aided Seattle Public Utilities in developing in-house capacity for their own climate research, and in applying climate data to their watersheds in an effort to help the utility, with over two million customers, respond to climate change impacts to their water supplies.[3] The research evaluating climate change impacts on Seattle's water supply watersheds was partially funded by the Joint Institute for the Study of the Atmosphere and Ocean (JISAO) under NOAA Cooperative Agreement No. NA17RJ1232, Contribution 1356 and by Seattle Public Utilities.[2] The water utilities engaged in contextualizing research, building and leveraging knowledge networks, and embracing an entrepreneurial approach to their research agenda through the co-production process.[6]

Benefits and Impacts

Seattle Public Utilities is now incorporating climate change science into both their short- and long-term planning and has achieved greater internal capacity for adapting to climate change.[3] The utility is developing adaptation strategies based on CIRC's NOAA RISA Team's input.[3] SPU climate researcher Paul Fleming acknowledges that the climate models are not perfect but clearly show that climate change will increase the magnitude and likelihood of drought events occurring.[4] The downscaled climate data enables the utility to update the water supply assessment and explore impacts on the intensity of forest fires, turbidity, the timing of fall rains, and precipitation in the city.[5]

Climate Adaptation Relevance

This watershed-specific climate modeling approach directly addresses the utility's need to understand and prepare for climate-driven changes in water availability and quality. The downscaled projections enable Seattle Public Utilities to assess how shifting precipitation patterns, reduced snowpack, increased wildfire risk, and drought events will affect the watersheds that serve over two million customers.[3][4] The ensemble modeling approach provides both most-likely scenarios and uncertainty ranges, allowing water managers to develop robust adaptation strategies that account for the full spectrum of potential climate futures.[2]

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