Effect of Climate Change on the Hydrology of the Chehalis Basin

Abstract

Recent flooding in the Chehalis basin has led managers, residents, and others to begin evaluating options for managing flood risk in the future (e.g., Ruckleshaus Center 2012). Climate change is expected to both increase the risk of winter flooding and decrease summer low flows – with implications for human communities and ecosystems alike. This document summarizes the results of a study aimed at providing initial estimates of the impacts of climate change on streamflow in the Chehalis River basin. The specific objectives of this work were to: 1. Refine projections of changing hydrology in the Chehalis River Basin, 2. Supply the larger project team with new inputs for hydraulic and ecosystem models, and 3. Evaluate the potential for climate change to alter the proportion of runoff originating above the proposed dam during flood events.