Carbonate (karst) aquifers constitute an important source of drinking water for large parts of the world population. Nevertheless, the stress on groundwater resources has increased significantly in recent decades in terms due to excessive pumping and the decrease of rainfall produced by climate change at many regions. Numerical models are important tools to improve water management. In this study, the simplified version of the semi-distributed VarKarst model has been improved to simulate piezometric variations in areas where the volume of pumping affects the groundwater level and the flow behavior is not typically karstic. This new version of VarKarst has been applied at the Torremolinos – Alhaurín de la Torre carbonate aquifer (Mijas Range, Southern Spain), which is characterized by a diffuse flow behavior caused by the high degree of fracturation and the low karstification developed in the marbles. The aquifer is overexploited nowadays, and additional water resources are necessary to supply drinking water to an important touristic region of Spain. To apply the new VarKarst model at this aquifer, simulated groundwater level dynamics were compared to piezometric level records from four representative pumping wells along Torremolinos – Alhaurín de la Torre aquifer. Eight years of simultaneous record of water level variations were used in the calibration procedure. The R2 and the root mean squared error (RMSE) of simulated and observed groundwater levels ranged from 0.90 to 0.99, and 0.36 m to 22.05 m, respectively. All observed trends of piezometric levels were correctly modeled. We conclude that the optimized simplified VarKarst numerical code can provide, in a first step, realistic hydrodynamic results in carbonate aquifers affected by pumping wells and with diffused flow behavior. In the near future, this numerical model could help to enhance the water management in karstic and fissured aquifers.
Keywords: modeling, VarKarst, carbonate (karst) aquifer, pumping wells, piezometric level