Hydrodynamic characterization of carbonate aquifers by atypical pumping tests without interruption of drinking water exploitation

Abstract

The Gran Sasso carbonate aquifer is the largest and most productive in the Apennines. Its hydrogeological structure has been studied since the middle of the last century for springs’ characterization for drinking purposes and for a motorway tunnel. Meanwhile, its hydrodynamic parametrization is less developed and is limited to monitoring the discharge and chemical and isotopic parameters. Secondary porosity characterizes the aquifer, and an underlying impermeable marly complex represents the basal aquiclude. It might appear inappropriate to characterize the hydraulic properties via pumping tests, as their reliability is proven in homogeneous and isotropic media. However, the high extent of the aquifer, the wells‘ location, the scarcity of information available and the lack of alternatives forced to estimate hydrodynamic parameters as in porous aquifers and to test the aquifer experimentally, especially in maximum pumping conditions. Since the aquifer testing was performed during the normal well field’s activities, it was not possible to perform typical tests. Therefore, the step-drawdown test was obtained by turning on an increasing number of wells over time and keeping fixed the observation points. As results, hydraulic conductivity, transmissivity, drawdown in operating condition, the influence radius and the flow directions have been obtained, without interrupting the water supply.