Capacité à satisfaire la demande en eau sous contraintes climatique et anthropique sur un bassin méditerranéen

Assessing water supply capacity is crucial to meet managers' needs, especially in the Mediterranean, one of the most vulnerable regions considering available water resources and where water demand has been increasing. The Hérault River catchment (2,500 km2, France) is a typical example of these issues as runoff significantly decreased since 1960. In this context, dynamics of water resource and demand evolution were analyzed over the past period. Then an integrated framework was developed over the last 50 years, combining a hydrological and
a dam management model, water demand estimation for the domestic and agricultural sectors through a historical reconstitution of water uses. This framework allowed to assess the frequency evolution of years when water demand could not be fully supplied at the portion scale. From 1961 to 2010, the unsatisfactory year frequency decreased in upstream portions due to farmland abandonment and renovation of irrigation networks. In the downstream portion where human pressures are the highest, the decrease in runoff and increase in water demand led to a fall of water supply capacity. Runs of the modelling framework at the 2050 horizon showed that the impacts of climate variability and water uses could be equivalent, but should affect different portions. Moreover, if mean annual temperature projections (+1.2 degree C) are confirmed, water demand mitigation scenarios would not be able to improve water supply capacity.