Quantification of the contribution of the Beauce groundwater aquifer to the discharge of the Loire River using thermal infrared satellite imaging

摘要

Seven Landsat thermal infrared (TIR) images taken over the period 2000–2010were used to establish longitudinal temperature profiles of the middle LoireRiver where it flows above the Beauce aquifer. The groundwater dischargealong the river course was quantified for each identified groundwatercatchment area using a heat budget based on temperature variations of theLoire River estimated from the TIR images. The results showed that 75 %of the temperature differences, between in situ observations and TIRimage-based estimations, remained within the ±1 °C interval. Themain discharge area of the Beauce aquifer into the Loire River was locatedbetween river kilometers 630 and 650, where there was a temperature drop of1–1.5 °C in the summer and a rise of 0.5 °C in winter.According to the heat budgets, groundwater discharge was higher during thewinter period (13.5 m3 s−1) than during the summer period(5.3 m3 s−1). These findings are in line with the results ofboth a groundwater budget and a process-based distributed hydrogeologicalmodel. Groundwater input was also found to be higher during the Loire's flowrecession periods.