This aquifer is shared by France and Switzerland, and a joint agreement for its management and protection was first signed in 1978. Other jointly agreed transboundary aquifers include, for example, those shared by Belgium and the Netherlands, Belgium and France, Austria and Hungary, Austria and Slovenia, and Spain and Portugal. For instance, on the basis of hydrogeological knowledge, ecological criteria and the presence of Natura 2000 sites, 34 groundwater bodies in the Scheldt River basin were identified as being in close connection with surface water. However, even for the well-established river basin commissions, addressing transboundary groundwaters is a new challenge.