The Flathead Lake Watershed (HUC 17010208) covers approximately 4,500 square miles in Montana, USA. Hydrologically, the watershed is fed by snowmelt, precipitation, and groundwater, with the main tributaries being the Flathead River, Swan River, and Stillwater River. In terms of snowpack, the Flathead Basin typically experiences a snowpack peak in April and May, which contributes to annual water supply. Flathead Lake, the largest natural freshwater lake in the western United States, is the main surface water feature in the watershed. Reservoir constituents include nutrients, sediments, and pollutants, which can contribute to algal blooms and water quality issues. Interesting climatic facts include the presence of microclimates due to varying elevations, and trends show increasing temperatures and decreasing snowpack in recent years, which could impact water supply and ecosystem health.