Effect of pumping in a coastal aquifer of limited thickness, Buenos Aires, Argentina

Abstract

In the northern sector of the Partido de La Costa, Argentina, the chemical quality of the groundwater was analyzed in the water supply area of the water utility cooperative. This resource is the only water source for consumption and is extremely vulnerable to contamination, both from the surface and from salinization processes. The impact of pumping was assessed to ensure the sustainable management of the water resources. Deep exploration wells were drilled, a monitoring network was implemented and water samples were obtained for chemical analysis. Continuously recording sensors were installed in the wells and geoelectrical methods were applied (vertical electrical soundings, electrical tomography). A chemical zonation was found at depth with a transition at 6 m. Calcium bicarbonate type water was identified above such a limit (Zone A) and sodium chloride type water below (Zone B), whose anion and cation concentrations exceed the limits set for drinking quality. In the sector where water extraction is most intensive, a deterioration of the chemical quality has been observed as a result of the salinization of the wells by water originating from Zone B. This phenomenon was identified by every method used. Electrical tomography allowed the measurement of the surface area defined by data of the individual wells. A reversal of the conductivity values occurred after the redistribution of the wells, which has been verified by the methods applied. A series of recommendations are offered to service providers for a more efficient management of the resources. The monitoring of the extraction areas is an essential tool to avoid processes of deterioration of the water resource.