Multi-Year Analysis Of Groundwater Temperature Fluctuations

Groundwater temperature (GWT) plays a significant role in biological, geochemical, and physical processes, influencing water quality. While GWT is known to be controlled through surface/subsurface water and energy fluctuations, the rate and extent of which this occurs remains poorly understood due to variation from depth, lithology, climate, and seasonality. Air temperature (AT) is noted as the primary control for shallow GWT (\u3e10 m); however, precipitation and tile drainage have been inferred to exhibit influence. The goal of this study is to understand how GWT might differ horizontally and vertically across a tile drained field. GWT was measured from nine wells at the T3 study site, north of Normal, Illinois, on a bi-weekly basis from June 2015 to August 2019. GWT (°C) and water elevation (m) was measured at depths 1.5, 2.3, 3.0-, and 4.6-meters depth from wells 2-12 and at 2.3-meters depth at wells 13,14, and 15. AT was measured on 15-minute intervals between June 2016 to March 2019, while precipitation measurements (cm) were obtained from Bloomington Airport using WeatherUnderground.com. Initial results display that horizontally, there is little difference between wells 2-15 further supported by ANOVA analysis, showing no variation. However, vertically, between the four depths, there is a noticeable muted response of GWT as depth increases, also supported by ANOVA analysis showing variation between 1.5 and 2.3-meters and 3.0 and 4.6-meters depth.https://ir.library.illinoisstate.edu/urs2021geo/1004/thumbnail.jp