Graduation Term

Summer 2025

Degree Name

Master of Science (MS)

Department

Department of Geography-Geology: Hydrogeology

Committee Chair

Eric Peterson

Committee Member

Wondwosen Seyoum

Committee Member

Lisa Tranel

Abstract

The use of Saturated Riparian Buffers (SRBs) in agricultural settings as a means of reducing contamination of surface water and groundwater resources has gained popularity due to their trapping ability and solute removal (nutrient recycling) capacity. In light of SRB’s nutrient-trapping and removal ability, numerous studies have been conducted to characterize the effectiveness of SRBs. However, most studies on SRBs have paid minimal attention to heterogeneity of hydraulic conductivity (K) and groundwater flow dynamics within SRBs. This study investigated the heterogeneity in horizontal K and estimated the vertical groundwater-specific discharge (qv) between the upper weathered and its underlying unweathered glacial units of an SRB, adjacent to a tile-drained agricultural farm field in Central Illinois. The glacial deposits at the study area are of the Tiskilwa Formation and are distinguished into an upper weathered diamicton, which is poorly sorted and coarsens with depth, and an underlying unweathered diamicton. For 23 wells, geometric mean K values were calculated after reducing multiple slug test data using the Hvorslev (1951) method. Geometric mean K values ranged from 1.92x10-4 m/s to7.63x10-6 m/s within the weathered diamicton, while the unweathered diamicton had K values as low as 4.79x10-9 m/s. Vertical hydraulic gradients (iz) calculated ranged from 0.03 to 0.8 from one-time measurements for both groundwater upwelling and downwelling. qv calculated from KV and iz ranged from 1.01x10-9 m/s to 4.30x10-13 m/s, while areas with high K had higher qv. The results of the study revealed flow towards the stream for shallow and intermediate groundwater, where the study area experienced groundwater downwelling and upwelling within the buffer zone. In conclusion, the study area exhibited heterogeneity depicted by the variation of K over orders of magnitude.

Access Type

Thesis-Open Access

DOI

https://doi.org/10.30707/ETD.1763755358.734347

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