The Marias Watershed (HUC 10030203) is located in Montana, covering an area of 6,200 square miles. The watershed is characterized by mountainous terrain, with elevations ranging from 3,000 to 8,000 feet, and includes the Rocky Mountain Front, the Marias Pass, and the Bears Paw Mountains. The hydrology of the watershed is largely influenced by snowpack, which accounts for up to 80% of the annual precipitation. The Marias River is the main watercourse, and feeds several reservoirs, including Tiber Reservoir, Lake Elwell, and Fresno Reservoir. The reservoirs are used for irrigation, as well as for recreational activities, such as fishing and boating. Interesting climatic facts include the fact that the Marias Watershed experiences both extremely cold winters and hot summers, with temperatures ranging from -40°F to 100°F. Climate trends in the region include an increase in precipitation and winter temperatures, as well as a decrease in snowpack.