THERMAL GRADIENT METHODOLOGIES IN GROUNDWATER AND SURFACE-WATER INTERACTIONS

Groundwater-surface water interactions are integral parts of the hydrologic cycle. Temperature is inexpensive and easy to monitor and as such, measuring temperature differences between groundwater and surface water is a potentially efficient method for evaluating their interaction. This study evaluated temperature as a methodology for studying groundwater-surface water interactions in the Brazos River Alluvial Aquifer, a minor aquifer for the State of Texas with the potential to be a significant water resource. As an influent stream, the Brazos River is dependent upon groundwater to maintain perennial flow. To study some of these effects thermometers, a high-temperature infrared laser, and temperature data loggers were used to gather temperature data in piezometers, at springs, and surface water bodies. A high-temperature infrared laser and thermometers were used to take instantaneous soil and water temperature readings, while temperature profiles at various surface water and groundwater sites were obtained using thermometers and temperature data loggers installed at various depths. Mini-piezometers and seepage meters were installed in surface water bodies in order to relate flow to the temperature data. The results suggested that the effectiveness of temperature measurements were highly dependent upon groundwater flow and the timing of the measurements. Although not applicable in all situations, temperature could be used in combination with mini-piezometers and seepage meters to quantify groundwater-surface water interactions. As such, these methods may be an efficient alternative to tracers and more invasive techniques.