The river L'Ouysse, located in the French department Lot, is a side branch of the river Dordogne. For 3/4 of its length the L'Ouysse runs underground and its path is mostly unknown. The actual spring of the river is located around the village Espeyroux in the north-east of the Lot. After heading south-west at the surface for around 10km the river disappears underground near the village Themines. Over the next 5km its path is unknown before it reemerges through 8km of explored passageways in the cave system Vitarelles. The final path of the river from the east end of the Vitarelles to the actual end of exploration from its final resurgence in a cave called Gouffre de Cabouy is currently still unknown. Starting from the resource Gouffre de Cabouy the river passes a sinkhole called Gouffre de Pou Meyssen after around 800m and after a total distance of 2km the end of sump 1 is reached. After sump 1 an air filled passage with a distance of 400m is followed by a short second sump of just 80m length followed by 700m of long dry streamway passage which also marks the actual end of surveying. Sump 3 has been explored for around 500m to a depth of -120m and is currently the actual end of exploration. The L'Ouysse is used as watersupply for the city Rocamadour and therefore it is of public interest to closely monitor this source of water and document its quality. To protect this water it is important to gain better knowledge about the underground path of the river, which is one of the main goals of this project.