Facing water shortage in a Mediterranean tourist area: seawater desalination or water reuse?

An integrated technical-economic modelling framework was developed to help planning and managing of water resources in a Mediterranean tourist area, Palma on Majorca island (Spain). Due to high water demand, groundwater resources are depleted and new water resources should be developed. Seawater desalination has become an important solution to water shortage, especially in the summer tourist season. Meanwhile, reclaimed water has been applied for agricultural and landscape irrigation. With regard to the treated wastewater not being effectively reused, further water reuse scenarios are envisaged in order to meet new water demand, restore over-exploited aquifers and reduce expensive seawater desalination. Three types of models were established and coupled: (i) hydrological models; (ii) water demand and/or need model; (iii) technical-economic model. In addition, a multi-criteria analysis completed the technical-economic modelling. The simulated water reuse scenarios are not alternative but complementary. They provide the possibilities for total reuse of wastewater in the Palma area. Compared with seawater desalination, water reuse is a cost-effective solution to address water scarcity issues in the Palma area. Using tertiary effluent for landscape irrigation allows over-exploited aquifers to recover. It is very attractive in terms of economic benefits and feasible with respect to technical and social aspects. Further water reuse for extending agricultural irrigation can greatly reduce seawater desalination but acquiring the farmers' agreement to give up pumping groundwater for irrigation would meet some difficulties. Water recharge would help to totally reuse wastewater but uncertainties related to public perception and the attitude or regulatory board and local authorities need dealing with. Because water reuse requires a long-term managing viewpoint in order to prepare and demonstrate its feasibility and security, seawater desalination was adopted as an emergency solution to meet peak demands during the tourist season and in case of drought.