Recharge to mountainous carbonated aquifers in SE Spain: Different approaches and new challenges J.M. Andreu a , F.J. Alcalá b, c , Á. Vallejos d , A. Pulido-Bosch d, * a Department of Earth Sciences and Environment, University of Alicante, AP 99, Alicante 03080, Spain b Estación Experimental de Zonas Áridas, CSIC, Almería 04120, Spain c Geo-Systems Centre/CVRM, Instituto Superior Técnico, Lisbon 1049-001, Portugal d Department of Hydrogeology, University of Almería, Almería 04120, Spain article info Article history: Received 29 May 2010 Received in revised form 11 January 2011 Accepted 16 January 2011 Available online 12 February 2011 Keywords: Modeling Mountainous carbonated areas Potential and actual recharge Remote sensing Semiarid Tracers abstract As in most semiarid regions, the main source of freshwater in SE Spain is its aquifers, and their exploitation has enabled the development of highly profitable irrigated agriculture and tourism indus- tries. The application of sustainable water management plans requires aquifer recharge to be quantified and its spatial pattern evaluated. This paper gives a comprehensive review of various recharge studies in mountainous carbonated aquifers, the most important groundwater reservoirs in SE Spain. Quantifica- tion of potential recharge rates and their spatial variability are illustrated using satellite-based modeling and tracer techniques. Actual recharge figures from the application of a lumped model based on water table fluctuations are also presented. Potential recharge relative to actual recharge is around 1 in small aquifers and flat areas and may increase up to 1.3 in heterogeneous mountainous aquifers with deep water levels due to losses of recharge in transit in the vadose zone. The complex interaction between climate, geology, aquifer geometry, topography, soil properties and the degree of karstification prevents the systematization of any particular technique to quantify potential recharge. The use of water table fluctuation methods for actual recharge evaluation requires daily time steps to compute unnoticed small recharge events. Therefore, the monitoring of environmental variables and the use of complementary techniques for comparison are recommended. Despite their importance for the correct assessment of recharge in the region, uncertainty analyses are still scarce, and the natural variability of recharge is unknown in most cases. Effort is required to improve the spatial and temporal characterization of recharge through the integration of interdisciplinary sciences. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction As in other arid and semiarid regions in the world, the scarcity and unpredictability of rainfall events and the lack of perennial rivers mean that aquifers are the main source of water resources in SE Spain (mostly Almería, Murcia and Alicante provinces, Fig. 1). The exploitation of aquifers has enabled the development of highly profitable irrigated agriculture and tourism sectors in the region (Pulido-Bosch et al., 2000; Bellot et al., 2007; Molina et al., 2009). Agriculture in the region supplies w20% of Spain’s total Gross Value Added supplied by this sector, accounting for more than 80% of the total water demand in the region and as much as 85% in some counties (Campo de Dalías, Campo de Cartagena, Altiplano de Murcia and Alto Vinalopó). Groundwater resources also meet an important fraction of the urban water demand: approximately 52% of urban supply in the province of Alicante (w2 million inhabitants) is supplied from aquifers. Aquifer overexploitation is closely associated with the main centres of tourism and agricultural development. Nowadays, most of the groundwater bodies in semiarid SE Spain are considered over- exploited or at risk (MMA, 2006). This situation has been partially triggered by weak administrative control on pumping rates and the limited understanding of the hydrogeological functioning of those aquifers. Environmental and social impacts have resulted from various groundwater processes, including salinization induced by seawater intrusion in coastal areas or by confined brines in some inland aquifers (Sánchez-Martos et al., 2007); land subsidence in alluvial aquifers (Mulas et al., 2003); groundwater pollution in irrigated areas (Pulido- Bosch et al., 2000); and desiccation or critical damage to wetlands and groundwater-fed ecosystems (Robledano et al., 2010). * Corresponding author. Tel.: þ34 950015465. E-mail address: apulido@ual.es (A. Pulido-Bosch). Contents lists available at ScienceDirect Journal of Arid Environments journal homepage: www.elsevier.com/locate/jaridenv 0140-1963/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.jaridenv.2011.01.011 Journal of Arid Environments 75 (2011) 1262e1270