Since 2023, the Regional Natural Park – UNESCO Global Geopark of the Causses du Quercy and the University of Bordeaux have combined their expertise to carry out an innovative study on the exchanges between the groundwater of the causse and that of the Célé river. As part of this study, in March 2024, using a drone equipped with a thermal camera, the team was able to observe mixing zones between surface water and groundwater. The latter, at stable temperatures (between 13 and 14°C), reveal their interactions with the watercourse depending on the seasons, where the temperature differences are well marked: from 5 to 10°C in winter and from 18 to 23°C in summer. This project, still in the experimental phase, takes on its full meaning in a complex karst context like that of the Causses. Indeed, groundwater, coming from networks of caves and cavities, can emerge directly into the bed of rivers without passing through the surface, as evidenced by the emergence of the Ressel at Marcilhac-sur-Célé. This device could soon be applied to other rivers in the region, such as the Dordogne and the Lot, to reveal new, previously unexplored underground flows. This study was made possible thanks to the support of the University of Bordeaux, the Department of Lot, the Adour Garonne Water Agency, the Occitanie Region, the Syded du Lot, the Syndicat Célé Lot Médian and the drinking water unions of Limargue Ségala, Causses Sud de Gramat and Pescalerie.
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