Aquifer recharge for securing water resources: the experience in Llobregat river.

The Llobregat Delta Aquifer has historically been a strategic water supply resource to the Barcelona metropolitan area. The use of river water combined with the exploitation of groundwater resources during dry periods has enabled the demographic and economic growth of the Barcelona area during the last fifty years. The aquifer overexploitation has entailed the decrease of groundwater level and the penetration inland of seawater intrusion. The main consequences have been the salinization of several wells and the deterioration of the groundwater quality. In this context, aquifer recharge has been practiced during nearly 40 years with the following objectives: (i) storing excess of water for times of less water availability, (ii) introducing an additional barrier for purification of water for a specific use and (iii) preventing the degradation of groundwater resources due to overexploitation or seawater intrusion. These methods, jointly with an efficient management of well extractions, have enabled to recover groundwater quality and therefore to guarantee the sustainable exploitation of such a vulnerable aquifer.