The Upper San Juan Watershed covers approximately 1,476 square miles in southwestern Colorado and northwestern New Mexico. The watershed includes the San Juan Mountains, which are the primary source of water for the region. The hydrology of the area is dominated by snowmelt, with the majority of streamflow occurring between April and July. The snowpack is also important for the area's water supply and recreation. The surface water in the watershed is primarily used for irrigation and municipal water supply, with some limited use for energy production. There are several reservoirs in the watershed, including Navajo Reservoir, which provides water for irrigation and flood control. Interesting climatic facts include the high altitude of the San Juan Mountains, which can experience significant snowfall even in the summer months. There are also trends of decreasing snowpack and increasing temperatures in the area due to climate change.