AN ALTERNATIVE APPROACH FOR EVALUATING WATER QUALITY RESPONSES TO AGRICULTURAL DITCH MANAGEMENT PRACTICES

Abstract

Six agricultural ditches were selected on Maryland's Eastern Shore to document the cumulative effect of multiple Best Management Practices on shallow groundwater nutrient concentrations and the associated receiving surface waters. Groundwater samples were collected over 18 months from 8 shallow wells installed in the unconfined aquifer at four ditches. Additional surface water samples were collected during the damming phase in all secondary ditches as well as the upstream and downstream sites on the primary drainage channel. Separate Multiple Linear Regression (MLR) models were used to determine the management practices which had the greatest influence in both groundwater and surface water. The variables "Ditch", "Buffer" and "Groundwater Level" were the most influential in predicting nutrient concentrations in shallow groundwater associated with drainage ditches. The MLR model for surface water concluded that the variables "Growing Season", "Rainfall" and "Ditch Cleanout" were superior for predicting surface water nutrients during the damming phase.