Integration of 3d geological models and groundwater flow models for the improvement of the management of complex multilayer aquifers under intensive exploitation. The case of the Loma de Úbeda (Southern Spain)

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Loma de Úbeda. Jaén province-Spain Geological, geophysical, hydrogeological, hydrochemical and isotopic data have been collected, which have made it possible to develop: a conceptual model of the aquifers hydrogeological functioning, a 3-D geological model and a numerical groundwater flow model that integrates all of the information obtained. The area of 1100 km 2 is occupied by three overlapping aquifers formed by Tertiary sands, Jurassic carbonates and Triassic sandstones. Between the three aquifers there are flow exchanges with water mixtures and a complex hydrogeological relationship. The whole system has been intensively pumped for olive irrigation, which has caused the drying up of areas previously saturated in the Jurassic carbonates. The interaction between the aquifers is complex and needs to be understood for efficient management. Once the geological geometry was modelled in 3-D and the hydrogeological functioning was defined, a flow modeling was carried out using MODFLOW, with the aim of validating the conclusions previously reached and providing the manager with an effective tool to reverse the undesirable processes caused by the intense exploitation. The flow simulation made is able to corroborate the results of previous studies on the way in which the mixing of infiltrated water occurs and provide the manager with a tool that will allow him to achieve a balanced and sustainable exploitation of these aquifers in the future. The hydrogeological functioning of complex, overlying and interrelated aquifers affected by intensive pumping is defined. This study integrates hydrogeological, structural geology, stratigraphy, and shallow and deep geophysics investigations. A 3-D geological model (GeoModeller) is integrated into a 3-D numerical flow model (MODFLOW). A 21-year period with 2 climatic cycles and a gradual increase in pumping is modelled.

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