The Willow Watershed (HUC 17040205) covers an area of approximately 1,689 square miles in central Idaho. It is characterized by a high elevation range, with peaks exceeding 10,000 feet in elevation. The watershed is fed by snowpack, which accounts for the majority of its surface water resources. The snowpack is highly variable and is influenced by a range of climatic factors, including temperature, precipitation, and wind. The watershed is home to several large reservoirs, which serve as important sources of water for irrigation and other purposes. The water in these reservoirs is typically high in dissolved minerals and other constituents, including nitrogen and phosphorous. Climate trends in the Willow Watershed have been characterized by increased temperatures and variability in precipitation patterns, which have implications for the timing and magnitude of snowpack accumulation and runoff.