Keywords:Groundwater resources Irrigation Wetlands conservation Multi-scale economic modeling
Water policies Cost-effectiveness analysisGroundwater in Spain, as in other arid and semiarid countries worldwide, has been widely used in the expansión of irrigated agriculture. In the Spanish Mancha Occidental aquifer, the excessive, and sometimes ¡Ilegal, water abstraction for irrigation has promoted outstanding socioeconomic development in the área, but it has also resulted in exploitation of the aquifer and degradation of valuable wetlands. Water policies implemented in the región ha ve not yet managed to restore the aquifer and face strong social opposition. This paper uses a multi-scale modeling approach to explore the environmental and socio-economic impacts of alternative water conservation measures at the farm and basin levéis. It also analyzes their comparative cost-effectiveness to help policy makers identify the least costly policy option for achieving the goal of the Mancha Occidental aquifer's sustainability. To conduct this analysis, a Mathematical Programming Model has been developed to simúlate: the closing-up and taxed-legalization of unlicensed wells, uniform volumetric and block-rate water prices, water quotas, and water markets. Aggregate results show that net social costs are not substantially different across policy option, so none of the considered policy options will be clearly more cost-effective than the others. However, there are significant differences between prívate and public costs (at the farm and sub-basin levéis), which will be critical for determining the application in practice of these policies. Results show that controlling ¡Ilegal water mining (through the legalization of unlicensed wells) is necessary, but is not sufficient to recover the aquifer. Rather, effective water management in this área will require the implementation of other water management policies as well. Among them, uniform volumetric and block-rate water pricing policies will entail the lowest net social cost, but will produce important income losses in the smallest and most water-intensive farms, which might put at risk the viability of these farms and the social acceptance of the policies. Further investigations on social costs, policy enforcement capacity and public participation in water management are highly recommended.