Water quality in the surficial aquifer near agricultural areas in the Delaware Coastal Plain, 2014

The U.S. Geological Survey, in cooperation with the Delaware Department of Agriculture, developed a network of wells to monitor groundwater quality in the surficial aquifer of the Delaware Coastal Plain. Well-drained soils, a flat landscape, and accessible water in the Delaware Coastal Plain make for a productive agricultural setting. As such, agriculture is one of the largest industries in the State of Delaware. This setting enables the transport of chemicals from agriculture and other land uses to shallow groundwater. Efforts to mitigate nutrient transport to groundwater by the implementation of agricultural best management practices (BMPs) have been ongoing for several decades. To measure the effectiveness of BMPs on a regional scale, a network of 48 wells was designed to measure shallow groundwater quality (particularly nitrate) over time near agricultural land in the Delaware Coastal Plain. Water characteristics, major ions, nutrients, and dissolved gases were measured in groundwater samples collected from network wells during fall 2014. Wells were organized into three groups based on their geochemical similarity and these groups were used to describe nitrate and chloride concentrations and factors that affect the variability among the groups. The results from this study are intended to establish waterquality conditions in 2014 to enable comparison of future conditions and evaluate the effectiveness of agricultural BMPs on a regional scale.