The Lower Illinois Senachwine Lake watershed covers an area of approximately 301 square miles in north-central Illinois. The hydrology of the watershed is characterized by several streams and rivers, including the Illinois and the Vermillion Rivers. The area experiences a humid continental climate, with hot summers and cold winters. The watershed receives an average of 33 inches of precipitation annually, with the majority falling as rain. The snowpack in the area varies depending on the severity of the winter, but typically ranges from a few inches to several feet. Surface water in the watershed is used for agricultural irrigation, industrial purposes, and to supply drinking water to local communities. Reservoir constituents in the area include fish, aquatic plants, and other wildlife. Trends in the area include increasing temperatures and changing precipitation patterns, which could have significant impacts on the hydrology of the watershed in the future.