The Upper Big Sioux Watershed (HUC 10170202) covers an area of 3,754 km² in southwestern Minnesota and northwestern Iowa. The watershed is characterized by an abundance of surface water, including numerous lakes, streams, and wetlands. The hydrology of the region is influenced by the snowpack, as the watershed receives an average annual snowfall of 52 inches. The watershed is also home to several reservoirs, including Lake Poinsett and Lake Thompson, which provide critical water resources for the region. Studies have found that the reservoirs contain high levels of nutrients, such as phosphorus, which can contribute to algae blooms and other water quality issues. Interesting climatic trends include increasing temperatures and more frequent extreme weather events, such as floods and droughts, which can have significant impacts on agriculture and other industries in the region.