296-6 Gaining or Losing? The Complicated Interaction of a Low-Gradient Stream and the Underlying Aquifer in Central Illinois.

Session: Innovations in Research of Groundwater-Surface Water Interactions over Multiple Spatio-Temporal Scales (Posters)

Presenting Author:

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Abstract:

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 is being studied in central Illinois to test the viability of a saturated riparian buffer at reducing nitrogen in soil and to ascertain the importance of groundwater flowing into the stream in the process. The goal of this study was to determine 1) whether the stream was gaining or losing water and 2) does the gaining or losing nature of the stream-aquifer system change seasonally? At both an upgradient and downgradient location, two wells were installed, one in the mobile stream bed and one in the underlying diamicton, to characterize the behavior of the stream. Conductivity, temperature, and depth (CTD) sensors recorded the elevation of the stream and the water levels within wells . Stream discharge was measured using the velocity-area method employing a Marsh-McBirney flow meter to measure velocity. By comparing rating curves made with discharge and stage data the gaining or losing nature of the stream can be accessed between the two well locations. Initial data for the upstream location showed that the water in the streambed possessed the highest head, suggesting water in the streambed would both upwell into the stream and downwell into the aquifer. During storm events, the stream stage rose above both the deep and shallow wells, and the stream temporarily served a losing stream. Based on the CTD data the downstream site is almost entirely a gaining stream with the stage below the heads of the shallow and deep wells, however, the stream bed sensor at the downstream location may not have been recording correctly for the first few months of data collection. The measured stream discharge data demonstrated  the upstream location consistently had a higher discharge than the downstream location, suggesting that the overall stretch of stream behaved as a losing stream.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-9135

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