LAND USE EFFECTS ON WATER QUALITY IN DELAWARE

Water is a critical resource in Delaware for agriculture, rural water supplies, and the tourism industry. However, according to Delaware's list of impaired waters, most of the state's surface waters are not meeting federal or state water quality criteria. As the state's population increases there is increasing pressure on the water resource from numerous sources, such as housing developments and wastewater treatment facilities. In July, 2005 a project was initiated to evaluate the impacts of these sources on the quality of surface water in Delaware. Presently, this project involves collecting water samples upstream and downstream of approximately ten locations; four suburban sites and six wastewater treatment plants. Water samples have been collected bi-monthly since August, 2005. Field measurements include stream flow rate, temperature, dissolved oxygen, pH, total dissolved solids, and conductivity. Laboratory measurements, conducted by the University of Delaware Soil testing laboratory, include nitrogen, phosphorus, potassium, aluminum, boron, calcium, copper, iron, magnesium, manganese, sulfur, and zinc.

To date over two hundred and fifty usable data points have been collected. Initial results indicate a large variation in water quality among both the suburban sites and the wastewater sites. To compare the effects of suburban versus wastewater treatment sites on surface water, a comparison of upstream to downstream water parameters was performed. The change in water quality parameters was calculated by subtracting downstream values from upstream values. There have been significantly larger changes at wastewater sites compared to suburban sites for the following properties: pH, conductivity, boron, sulfur, and iron. In general, wastewater sites had larger conductivity and sulfur values downstream of the facility, as opposed to upstream, than did suburban areas.

This project has recently expanded to include more sites from both established housing developments and newer developments in the hopes of evaluating advances in water quality protection procedures initiated during construction. Results from this project will help to evaluate the impact of housing developments and wastewater treatment facilities on the quality of surface waters in Delaware.