The Mackinaw watershed (HUC 07130004) covers approximately 1,476 square miles in central Illinois, draining into the Illinois River. The area experiences a humid continental climate with hot summers and cold winters, and receives an average of 34 inches of precipitation per year. Winter snowpack can have a significant impact on streamflow during the spring melt season. Surface water in the watershed is heavily influenced by agricultural practices, with high levels of sediment and nutrients contributing to water quality issues. The three main reservoirs in the watershed are Lake Bloomington, Evergreen Lake, and Lake Sante Fe, which are used for drinking water, recreation, and flood control. Climatic trends in the region show an increase in average temperatures and precipitation over the past century, with more extreme weather events such as heavy rainfall and flooding becoming more common. Efforts to improve water quality and reduce nutrient runoff from agricultural practices are ongoing in the Mackinaw watershed.