The Upper Yellowstone Watershed (HUC 10070002) covers an area of approximately 11,700 square miles in Montana and Wyoming. It is characterized by high-elevation mountain ranges, vast grasslands, and open forested areas. The hydrology of the watershed is dominated by the Yellowstone River and its tributaries, which provide critical water resources for irrigation, recreation, and wildlife. The snowpack in this region is typically deep and persistent, with some areas receiving over 400 inches of snow annually. Surface water quality in the watershed is generally good, with only minor impacts from agricultural and urban development. There are several reservoirs in the watershed, including the Yellowstone Lake, which is an important source of water for the region. The climate of the watershed is characterized by cold winters and warm summers, with temperatures ranging from -20°F to 90°F. In recent years, there has been a trend towards milder winters and earlier snowmelt, which has implications for water availability and ecosystem health.