Salt lakes and coastal aquifers
Our workgroup is currently involved in the investigation of salinisation processes in 2 different hydrological environments in cooperation with the Spanish Geological Survey (IGME) and the Granada University. One study area is a costal aquifer (Velez Aquifer) and the second is the biggest salt lake of western Europe and is called the Fuente de Piedra Salt Lake. Both locations are concerned by climate change during the last decades leading to decreasing precipitation in this area. This gives rise to salinisation processes which seriously threat the regional fresh water resources. Although several modelling and field studies have been published in the literature during the last decades these systems are still not very well understood and much research is required in order establish reliable management systems for the future drinking water supply.
A current research tries to characterise the flow regime and interrelation between surface water and groundwater in a salt lake basin by means of stable isotopes, hydrogeochemical and hydraulic data. During three sampling campaigns (Feb. 2004, Feb. 2005 and Oct. 2005) ground- and surface water samples were collected for stable isotope studies (18O, D) and for major and minor ion analysis. Hydraulic measurements at multilevel piezometers were carried out at 4 different locations around the lake edge. Conductivity logs were performed at 4 piezometers located along a profile at the northern lake border and at two deeper piezometers in the Miocene basin at a greater distance to the lake. In order to describe processes which control the brine evolution different hydrogeochemical simulations were performed. Hydrogeochemical data show a huge variety of brines related to thickness variations of lacustrine evaporites around the lake. Salinity profiles in combination with stable isotope and hydraulic data yield the existence of convection cells and recycled brines. Furthermore restricted flow regimes of meteoric groundwater inflow into the lake were detected. Dedolomitisation processes could be identified by hydrogeochemical simulations and different brine origins were reproduced by different inverse modelling approaches.