Assessing nutrient concentrations and field-scale seepage load under an automated drainage water management system in Ohio

Abstract

Automated drainage water management (ADWM) leverages technological advancements to control flow volumes and nutrient loads leaving farm fields through the ADWM system outlet while also promoting lateral groundwater seepage through the edge of the field (EOF). The main objective of this study was to assess the impact of ADWM on nutrient concentrations, namely total nitrogen (TN) and total phosphorus (TP), in groundwater and soil water sampled within and across the EOF for an agricultural field located in northcentral Ohio. Water samples collected from shallow groundwater wells showed that TP and TN concentrations were higher at the EOF relative to in the field while water samples collected from suction lysimeters showed that TP and TN concentrations were higher in the field relative to at the EOF. Further, seasonal nutrient loads across the EOF as lateral groundwater seepage were estimated using an application of the Riparian Flow-Concentration Integration method. We found that the maximum contribution of flow volume and nutrient load across the EOF as lateral groundwater seepage occurred in Spring while minimum contributions occurred in the Winter compared to other seasons of the year. The ADWM system considered in this study, which was programmed to automatically open based on water level rise in the outlet structure, appears to achieve the greatest potential for reductions in nutrient load during Winter by altering flow pathways from the drainage system through the EOF.