Characterisation of mountain-Mediterranean karst aquifers as lighthouses for the assessment of global change impacts in the Mediterranean region: the Sierra Seca aquifer system (SE Spain)

The Sierra Seca aquifer system is in the NE of the province of Granada, in the Prebaetic Domain (Baetic Cordillera). It is composed of two hillslope karst aquifers hosted in the Lower Cretaceous and Upper Cretaceous limestones, respectively. Aquifer recharge is a process that occurs along the slope of such limestone outcrops. This work has two objectives: to estimate the recharge of the Sierra Seca aquifer system and to assess the impact of climate change on this recharge. The mean recharge of the aquifer system (${\overline{q}}_R$) and the recharge efficiency ($\xi$) are estimated by two complementary approaches: (1) using a semi-distributed rainfall-runoff model (HBV model), and (2) using the chloride content of the recharge as an environmental tracer (CMB model). The estimates of ${\overline{q}}_R$ obtained by both approaches are similar, being 277 mm/yr and 266 mm/yr for HBV and CMB, respectively. Similarly for $\xi$, the values are 50.5 % and 48.5 % for HBV and CMB. The impact of climate change on recharge is estimated from the relationship between precipitation and recharge observed in the carbonate-karst aquifers of the Baetic-Cordillera system (S Spain). The Sierra Seca aquifer system will be significantly affected, with a reduction in recharge of >75 %, regardless of the IPCC climate change scenarios, RCP2.6, RCP4.5 and RCP8.5, considered.