The Upper Tongue Watershed (HUC 10090101) covers an area of approximately 1,500 square miles in northeastern Wyoming and southeastern Montana. The watershed is predominantly mountainous, with elevations reaching up to 10,000 feet above sea level. The hydrology of the area is characterized by a snowmelt-dominated regime, with the majority of streamflow occurring during the spring and early summer months. The watershed is home to a variety of surface water sources, including small creeks, large rivers, and several reservoirs. The snowpack in the region is influenced by the Pacific Ocean, with a significant portion of the snowpack typically accumulating during the months of February and March. The area is also subject to extreme weather patterns, such as heavy snowfall and freezing temperatures during the winter months. Climate trends suggest that the region is becoming warmer and drier, which could impact the water supply and overall ecosystem of the watershed.