The Middle Potomac Anacostia Occoquan Watershed (HUC 02070010) is located in the eastern United States and covers an area of approximately 3,360 square miles. The hydrology of the watershed is dominated by the Potomac River and its tributaries, including the Anacostia and Occoquan Rivers. The watershed experiences a humid subtropical climate with hot summers and mild winters. The area receives an average annual precipitation of 42 inches, with the majority falling as rain. Snowfall is infrequent and typically light, with an average of 15 inches per year. The surface water quality in the watershed has been impacted by urbanization and agricultural activities, leading to high nutrient and sediment loads. The Potomac River serves as the primary source of drinking water for millions of people in the Washington D.C. metropolitan area, and water quality improvements have been ongoing since the 1970s. The watershed is also home to several reservoirs, including the Potomac and Occoquan Reservoirs, which are used for drinking water supply and recreation.