New Projections of Changing Heavy Precipitation for Thurston County


Mauger, G.S., J.S. Won, 2019. New Projections of Changing Heavy Precipitation for Thurston County. Report prepared for the Thurston County Department of Public Works. Climate Impacts Group, University of Washington, Seattle.


Recent research suggests that future heavy rain events will be more intense in the Pacific Northwest (e.g., Warner et al. 2015). Past studies have not accounted for this change, either because the methods cannot reliably capture changes in rainfall intensity (e.g., Abatzoglou and Brown 2012), or because previous studies did not evaluate changes in short-duration precipitation (e.g., hourly) that are of relevance to stormwater planning (e.g., Salathé et al. 2010).

The purpose of this project was to develop projections of 21st century changes in precipitation that can be used to inform stormwater and wastewater management in Thurston County. The work was funded by the Thurston County Stormwater Utility.

The specific objectives of the project were to:

1. Produce three new Regional Climate Model projections: Evaluate global models and develop projections representing a range of potential changes in 21st century precipitation extremes.

2. Synthesize projections to support stormwater planning needs: Develop hourly precipitation time series (1970-2099) for hydrologic model input points. Evaluate changes in the intensity, duration, and magnitude of heavy precipitation events at specific locations across the county. In addition, provide gridded estimates of changing precipitation statistics that can be used to evaluate differences in risk across the county.