Graduation Term

Spring 2026

Degree Name

Master of Science (MS)

Department

Department of Geography-Geology: Hydrogeology

Committee Chair

Eric Peterson

Committee Member

Lisa Tranel

Committee Member

Wondwosen Seyoum

Abstract

While the seasonal behaviors of low-gradient streams have been studied, the behavior of surface water and groundwater interactions within low-gradient streams in glaciated terrain is not fully understood. A third order, low-gradient glacial stream with a saturated riparian buffer in central Illinois was studied to determine the direction of flow between the surface water and groundwater. The goals of this study were to determine 1) whether the stream was gaining or losing water, and 2) whether the gaining or losing nature of the stream-aquifer system changes seasonally. At both an upgradient and downgradient location, two wells were installed: one in the mobile streambed and one in the underlying diamicton surficial aquifer, to characterize the hydrologic conditions of the stream. Conductivity, temperature, and depth (CTD) sensors recorded the elevation of the stream and the water levels within the wells. Stream discharge was measured using the velocity-area method employing a flow meter to measure stream water velocity. By comparing rating curves generated with discharge and stage data, the gaining or losing nature of the stream was assessed between the two well locations. CTD data showed that the highest head was consistently the surficial aquifer, and the lowest head was the stream stage resulting in an upwards hydraulic gradient and an upwelling of groundwater into the stream, making the T-3 stream a gaining stream. This upwelling condition changed only during storm events when the stream stage briefly rose above the heads of the streambed and surficial aquifer, altering the hydrological conditions to a losing stream for periods of one to two days. Despite being a hydrologically gaining stream, discharge decreased between the upstream and downstream locations as water was lost to evapotranspiration, and stream stage decreased over time. The decrease in stream discharge was most likely due to the low hydraulic conductivity of the glacial surficial aquifer. The low influx of about 10-6 m3/s of upwelling groundwater was not enough to offset the water lost to evaporation and plant uptake and resulted in the stream drying up in mid-September despite being a gaining stream for nearly the entirety of the study period, even after the stream held no standing water.

Access Type

Thesis-Open Access

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