MONITORING TEMPERATURE AS A TRACER AT THE GUARANI AQUIFER SYSTEM OUTCROP ZONE
Temperature values have been registered in the monitoring wells and stream since 2011. The groundwater temperature is constant, with a mean value of 23.48 ± 0.13 °C. Stronger variation is observed for the stream temperature, which has a mean of 21.01 ± 2.18 °C, with a maximum and minimum of 25.19 and 14.93 °C, respectively. Based on these temperature data, our hypothesis is that the temperature could be used as tracer to evaluate stream–aquifer interaction, especially in the winter (June to August), when larger temperature differences between the aquifer and stream are observed. Preliminary results using a temperature probe with four thermistors confirmed our hypothesis along Onça Creek. In the next step, fiber-optic distributed temperature sensing was applied to measure synoptic high-resolution temperature distributions at both fine spatial and temporal scales and to identify stretches with gaining behavior. The collected data and research findings provide important background measurements and evaluations relevant to long-term monitoring needs within the Guarani aquifer system.