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Publication Date
2025
Document Type
Poster
Degree Type
Graduate
Mentor
Dr. Eric Peterson
Mentor Department
Geography, Geology and the Environment
Co-Mentor
Dr. Wondwosen Seyoum
Co-Mentor Department
Geography, Geology and the Environment
Keywords
Hydraulic Conductivity, Heterogeneity, Groundwater, Specific discharge, Upwelling, Downwelling
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. Considering 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 how heterogeneity of hydraulic conductivity (K) contributes to the effectiveness of SRBs. The heterogeneity of K has been proven to be, if not the most significant, one of the contributing factors to the effectiveness of SRBs since heterogeneity in K controls water fluxes and solute trapping efficiency. This study investigates the heterogeneity in horizontal K and estimates the vertical groundwater-specific discharge (qv) between the upper weathered and its underlying unweathered glacial units of an SRB, adjacent to a tiledrained 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 clay, which becomes coarser and poorly sorted with depth, and an underlying unweathered diamicton. The diamicton comprises a clay-dominated matrix with coarser sediment, resulting in a poorly sorted unit. For 23 wells, geometric mean K values were calculated after reducing multiple slug test data using the Hvorslev (1951) method. From the data analysis, mean K values from individual wells ranged from 1.92 x 10-4 m/s to 7.63 x 10-6 m/s within the weathered diamicton, whereas the unweathered diamicton had K values as low as 4.79 x 10-9 m/s. Typical hydraulic gradients (iz) values ranged from 0.03 to 0.1 from one-time measurements. qv was computed as the product of the average vertical hydraulic conductivity (KV) and vertical hydraulic gradients (iz) between depths of 1.5m and 4.6m, as these depths represent locations in the weathered and unweathered diamicton, respectively. The results of the study confirm the conceptual model for shallow and intermediate groundwater flow where the study area experiences downwelling further away from the buffer zone with groundwater upwelling areas within the buffer zone. The qv ranged from 1.25 x 10-7 m/s to 4.30 x 10-10 m/s, where areas with high K had higher qv, suggesting higher dilution of nitrate, which is confirmed by past studies from the study site. In conclusion, the study area exhibits heterogeneity depicted by the variation of K over orders of magnitude and accounts for the dynamic flow of water within the SRB.
Recommended Citation
Awuku, Joseph; Peterson, Eric; Seyoum, Wondwosen; and Tranel, Lisa, "Investigating Heterogeneity of Hydraulic Conductivity and its Influence on Groundwater Flow Dynamics within a Saturated Riparian Buffer in Central Illinois" (2025). University Research Symposium. 513.
https://ir.library.illinoisstate.edu/rsp_urs/513
