The Lower Potomac Watershed (HUC 02070011) covers an area of 3,315 square miles in Virginia and Maryland, draining into the Chesapeake Bay. The hydrology of the watershed is influenced by the Potomac River, which flows into the Chesapeake Bay. The area has a moderate climate, with average temperatures ranging from 25°F in the winter to 85°F in the summer. The annual precipitation is around 43 inches, with most of it occurring during the summer months. Snowfall is minimal, with an average of 15 inches per year. The surface water quality in the watershed is generally good, with some stream segments experiencing high levels of bacteria and nutrients. The reservoirs in the area are important sources of drinking water for the region, and constituents include suspended solids, nutrients, and metals. Interesting climatic trends in the area include an increase in average annual temperature and a decrease in total annual precipitation over the past few decades.