The Grand Watershed (HUC 10130303) covers an area of approximately 2,380 square miles in southwestern Colorado. The hydrology of the watershed is dominated by snowmelt, with the majority of streamflow occurring in the late spring and early summer months. The watershed contains several high-elevation areas with specific snowpacks, including the San Juan Mountains and the La Plata Mountains. Surface water in the watershed is primarily supplied by the Animas River and its tributaries, including Cement Creek and Mineral Creek. The watershed also contains several reservoirs, including Navajo Reservoir and Lemon Reservoir, which are used for irrigation, recreation, and flood control. Interesting climatic facts and trends in the watershed include the prevalence of drought conditions in recent years, particularly during the summer months, and a trend towards warmer temperatures and earlier snowmelt due to climate change.