The Lez karst system is located in southern France, north of Montpellier. The Lez spring is the main outlet of the aquifer. The catchment of this karst spring extends over an area of about 380 km². Approximately a third of this area is dominated by karstic outcrops and contributes to the recharge of the aquifer.
The Lez spring has been supplying the city of Montpellier with water since the 19th century (1854). At the end of the 1970s, increased demand for drinking water motivated managers to drill deep wells into the main karst drain upstream of the spring. The maximum pumping rate is fixed at 1700 l/s so that the minimum water level falls no lower than 35 meters above sea level.
Data and information for the Lez catchment has been collected as part of a project with the Bureau de recherches géologiques et minières (BRGM). This makes it an ideal transfer location for the MedWater project.