Characterising flow regime and interrelation between surface-water and ground-water in the Fuente!de Piedra Salt lake basin by means of stable isotopes, hydrogeochemical and hydraulic data

This research reports the characterisation of ground- and surface-water interaction in the Fuente de Piedra Salt take basin in southern Spain by a combined approach using hydraulic, hydrogeochemical and stable isotope data. During three sampling campaigns (February 2004, 2005 and October 2005) ground- and surface-water samples were collected for stable isotope studies (O-18, D) and for major and minor ion analysis. Hydraulic measurements at multilevel piezometers were carried out at four different locations around the take edge. Conductivity togs were performed at four piezometers located along a profile at the northern take border and at two deeper piezometers in the Miocene basin at a greater distance from the take. To describe processes that control the brine evolution different hydrogeochemical simulations were performed. Hydrogeochemical data show a variety of brines related to thickness variations of lacustrine evaporites around the take. Salinity profiles in combination with stable isotope and hydraulic data indicate the existence of convection cells and recycled brines. Furthermore restricted ground-water inflow into the take was detected. Dedolomitisation processes were identified by hydrogeochemical simulations and different brine origins were reproduced by inverse modelling approaches. (C) 2007 Elsevier B.V. All rights reserved.