Monitoring and Evaluation of Water Quality in Silver Lake, Delaware

The Silver Lake located in Dover, Delaware is an open water body covering 130 acres of surface area. Despite its important recreational functions, the lake has been stranded with water quality issues for more than twenty years. Remediation approaches such as installing constructed wetlands and stormwater forebays at the upstream waterways to trap sediments and pollutants were implemented; other methods including injecting alum to reduce the P content of lake water are being proposed. Due to lack of systematic monitoring, the current status of water quality in the Silver Lake remains obscure to the public. The objectives of this study were to evaluate the overall water quality of the Silver Lake and to identify principle pollution factors. Monitoring locations at the upper, middle, and lower stream of the lake were selected and water was measured on-site for monthly changes in temperature, dissolved oxygen (DO) content, pH, salinity, turbidity, and light penetration over six months. Monthly water samples were collected for a whole year and analyzed for Chlorophyll a, dissolved organic carbon, dissolved nitrogen, and reactive phosphorus contents. It was revealed that the Silver Lake water was still heavily contaminated by N, P nutrients and suspended particles. During the fall season, the lake water contained dissolved N up to 5 mg/L, dissolved reactive P up to 100 µg/L, and dissolved organic carbon up to 50 mg/L. The pH of the water was as high as 9.7 and chlorophyll a 14,700 µg/L, while the Secchi disk depth as low as 0 cm and DO 6.9 mg/L at 5°C. The results suggest that intensive soil conservation practices and appropriate land use management are necessary to restore the Silver Lake.