Identifying water sources in a karst aquifer using thermal signatures

Using thermal data, a unique approach to delineate flow components in a karsts aquifer was conducted. Thermal signatures from seven wells and six springs were analyzed to determine potential relationships among different storage reservoirs and the air temperature. The temperature signatures revealed three distinct reservoirs: epikarst, shallow groundwater, and deep groundwater. The reservoirs have different thermal signatures and relationships with the air temperature. During a wetter period, the epikarst water temperatures more closely follow the air temperature trend and are closer in value, but during drier conditions, the shallow groundwater temperatures are more similar in value to air temperature. Deep groundwater temperatures show no relationship to variations in surface air temperature. Using the water temperatures from the three reservoirs, the sources of water at two major springs, Copperhead and Langle, were delineated. During the wetter period, the shallow groundwater and the epikarst were the primary contributors of water to the springs. As conditions became drier a transition occurred, the deep groundwater became the major source of water to the springs. Variation in temperatures of waters at Copperhead and Langle spring is a result of the epikarst and the shallow groundwater, which represents ineffective thermal reservoirs.