Graduation Term

2023

Degree Name

Master of Science (MS)

Committee Chair

Wondwosen M Seyoum

Abstract

Loss of nutrients, such as nitrogen and phosphorous, from agricultural lands in the Midwest affects farm productivity and environmental quality. Nutrient runoff from lands discharged into streams degrades the aquatic ecosystem through eutrophication and subsequent hypoxic conditions. The presence of nitrogen also threatens the potability of numerous aquifer bodies globally due to their high solubility in water. To tackle this problem, best management practices such as Saturated Buffer Zone (SBZ) are implemented to reduce nitrogen from nitrate-laden tile water from agricultural lands before being discharged into streams. Groundwater flow and interactions at SBZ are not well understood. To aid the understanding of groundwater flow in the SBZ with the T3 site as a case study, this project aims to understand the interaction between groundwater flow and local tile water flow and the influence of tile water on the groundwater with varying the rate of discharge of tile water. Finite difference groundwater modeling code (MODFLOW) was used to produce a three-dimensional steady-state groundwater model. After calibration using manual and autocalibration techniques, several scenarios were run with variable tile discharge rates, and the resulting change in groundwater flow direction using particle tracking code - MODPATH was analyzed. The results demonstrated that the influence of groundwater flow on tile flow reduces with a nonlinear trend as tile discharge increases. The field of influence of tile water on local groundwater logarithmically increases as tile discharge increases. This has a direct implication on the effectiveness of the SBZ in reducing nitrate and hence their design.

Access Type

Thesis-Open Access

DOI

https://doi.org/10.30707/ETD2023.20231004061829773908.999950

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