The Upper Chehalis Watershed (HUC 17100103) covers approximately 263,000 acres in southwestern Washington state. The Chehalis River is the primary hydrological feature of the watershed, with numerous tributaries and smaller streams also contributing to the flow. The area receives significant precipitation, with an average of 88 inches per year, and has a diverse range of habitats including forests, wetlands, and agricultural land. The watershed is also home to several species of fish, including steelhead and Chinook salmon, which are important for both recreational and commercial fishing. Climate trends in the region include an increase in average temperatures and a decrease in snowpack, which has potential implications for water availability and streamflow in the future. In recent years, the area has experienced flooding and landslides due to heavy rainfall and soil saturation. The reservoirs in the watershed are primarily used for flood control and irrigation purposes.