Hydrogeochemistry of a wetland area of southwestern Sicily (Italy)

The “Preola” and “Gorghi tondi” lakes are the most noticeable wetlands in the Mazara del
Vallo territory (south-west Sicily). There are four karst origin lakes located in a natural
depression formed by gypsum dissolution and subsequent collapse of the “Calcarenite di
Marsala”, a few meters above sea level.
Erosion of the depression sides and human activity has caused visible colluvial deposits,
which have contributed to a natural filling process of the lakes.
A hydrogeological map of the area and the reconstruction of a water circulation model
supplying the lakes have been drafted from geochemical and hydrogeological data.
It is apparent from 18O values that the well waters are mainly fed by local meteoric water
circulating within the calcarenitic aquifer. However, the lake waters chemical composition are
very likely controlled by evaporation processes and a complex mixing between seawater and
groundwater, depending on seasonal variation in the hydrodynamic equilibrium.