The South Fork Sangamon Watershed covers approximately 1,045 square miles in central Illinois. The area is largely agricultural and is home to many small towns and communities. The hydrology of the watershed is primarily characterized by the South Fork Sangamon River and its tributaries, which drain into Lake Springfield, a large reservoir in the area. Snowpack is variable from year to year and can impact water availability in the spring. Surface water in the watershed is generally considered to be of good quality, although there are some concerns about nutrient levels and sedimentation in some areas. Lake Springfield is an important source of drinking water for the region, and the reservoir is regularly monitored for contaminants. Interesting climatic facts and trends include the increasing frequency of heavy rainfall events, which can contribute to localized flooding in the area.