Estimation of surface runoff for calculating recharge in the karstic massif of Ports of Beseit (Tarragona, Spain) combining water balance in the soil and analysis of flow hydrographs

Abstract

For the right estimation of aquifer recharge by precipitation surface taking into account runoff is particularly relevant. Non considering it in the estimation of the groundwater resources can overestimate them. In the Baix Ebre aquifer system, in southern Catalonia, the surface and vadose zone runoff produced in the karstified carbonate formations in the Ports de Beseit massif has to be evaluated in order to achieve a better estimation of the resources transferred from this massif to the Plana de La Galera plain. Starting from the conceptual hydrogeological model, the average annual runoff is estimated. It includes the discharge from temporal perched aquifers in the Ports de Beseit massif, in the Matarraña river basin, and in the SE watershed to the Plana de La Galera plain. This is performed by analyzing the river and tributaries hydrographs, the filling and emptying hydrographs of the Ulldecona reservoir, and the soil water balance using the Visual Balan code applied to obtain the runoff in the Ulldecona reservoir watershed. The runoff has been estimated about 105±20 mm·yr⁻¹, which represents 20–30% of average annual recharge in the Ports, estimated with soil water balance and atmospheric chloride deposition balance, about 350–500 mm·yr⁻¹, which is mostly transferred laterally to the Plana de La Galera plain.