In 1996, Illinois listed Lake Decatur for phosphorus and nitrogen pollution. 25 years later, 3 grants helped Decatur expand BMPs and improve water quality in the lake

Lake Decatur was added to Illinois' Clean Water Act Section 303(d) list of impaired waters in 1996 for phosphorus and nitrogen pollution caused by agricultural runoff. Twenty-five years later, the City of Decatur expanded its work to reduce sediment and nutrient loading through the Lake Decatur Water Quality Initiative.

Monitoring data has since shown promising trends for phosphorus, dissolved oxygen, and nitrogen/nitrates, although continued effort is needed to protect the lake.