Hydrochemical and isotopes studies in a hypersaline wetland to define the hydrogeological conceptual model: Fuente de Piedra Lake (Malaga, Spain)

Abstract

The Fuente de Piedra lake is a hypersaline wetland of great extension (13.5 km2 ) and rich in aquatic birds and other species. It became therefore the third Spanish wetland to be included in the Ramsar convention and has been a “nature reserve” since 1984. The lake has an endorheic basin (150 km2 ) with variable-density flows dominated by complex hydrogeological conditions. The traditional conceptualization of endorheic basins in semiarid climates considered that the brine in this hydric system was exclusively of evaporative origin and was placed only in the lake and its surrounding dis charge area in the basin. Previous geophysical and hydrochemical studies identified different types of waters and brines. In this work, natural tracers (Cl− , Br− , Na+ , Mg2+ ) and environmental isotopes ( 18O, 2H, 14C, 13C and 3H) were employed to a) discriminate different types of brines according to their degree of evaporation and genesis, and b) to estimate res idence times of brine waters and identify recharge areas of the different flow subsystems. A conceptual model of the hydrogeological system of the lake basin and its links to a regional karst system is proposed