Heat tracing to examine seasonal groundwater flow beneath a low-gradient stream in rural central Illinois, USA | Traçage thermique pour étudier l’écoulement saisonnier de la nappe sous un cours d’eau à faible gradient, dans le centre rural de l’Illinois, Etats-Unis Trazado de calor para examinar el flujo estacional del agua subterránea por debajo de una corriente de bajo gradiente en la zonas rural central de Illinois, EE.UU 利用热量示踪检验美国伊利若斯州中部农村地区一条低坡度河流之下的季节性地下水水流 Traçador térmico para analisar o fluxo de água subterrânea sazonal sob um córrego de baixo gradiente na região rural central de Illinois, EUA
2016
Bastola, Hridaya | Peterson, Eric W.
The thermal profile of a streambed is affected by a number of factors including: temperatures of stream water and groundwater, hydraulic conductivity, thermal conductivity, heat capacity of the streambed, and the geometry of hyporheic flow paths. Changes in these parameters over time cause changes in thermal profiles. In this study, temperature data were collected at depths of 30, 60, 90 and 150 cm at six streambed wells 5 m apart along the thalweg of Little Kickapoo Creek, in rural central Illinois, USA. This is a third-order low-gradient baseflow-fed stream. A positive temperature gradient with inflection at 90-cm depth was observed during the summer period. A negative temperature gradient with inflection at 30 cm was observed during the winter period, which suggests greater influence of stream-water temperatures in the substrate during the summer. Thermal models of the streambed were built using VS2DHI to simulate the thermal profiles observed in the field. Comparison of the parameters along with analysis of temperature envelopes and Peclet numbers suggested greater upwelling and stability in temperatures during the winter than during the summer. Upwelling was more pronounced in the downstream reach of the pool in the riffle and pool sequence.
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