The Willow Watershed (HUC 17070104) covers approximately 966 square miles in central Utah. It is part of the Colorado River Basin and contributes to the Green River. The watershed is dominated by mountainous terrain with elevations ranging from 4,000 to 12,000 feet. Willow Creek is the main stream in the watershed, which has a well-defined snowmelt hydrology. The snowpack in the watershed is typically deep and persistent, with the highest elevations receiving up to 600 inches of snow annually. Surface water in the watershed is used for irrigation and domestic purposes, and there are several reservoirs, including Joes Valley Reservoir, which provide water storage for downstream users. The climate in the Willow Watershed is semi-arid, with average annual precipitation ranging from 9 to 30 inches. Recent trends show a decrease in snowpack and earlier snowmelt due to warming temperatures.