The purpose of this study was to suggest the alternative measures to properly manage the water quality of Lake Euiam, Chuncheon. Current pollution level of Gongji stream (influent to Lake Euiam) and sources of contamination in Lake Euiam were investigated. Particle size, organic matter and nutrient contents, heavy metals were analyzed for sediment samples taken from lower region of Gongji stream. Average organic matter content of nine sediment samples was 5.7%, and for nitrogen and phosphorus it was 750 mg/kg and 977mg/kg, respectively. Heavy metals including aluminum, iron, manganese and zinc were measured, whereas Cd and As were not detected. Effluent from Chuncheon Wastewater Treatment Plant appeared to be one of the main cause of organic matter and nutrients level in Lake Euiam. Inhibition of primary production and consequent reduction of organic matter content within the Lake should be a key measure to protect the water quality of Lake Euiam. Preventive measures to reduce the level of nutrients in wastewater treatment effluent were found necessary.