Unconventional pumping tests in carbonate, alluvial and complex aquifers, without interruption of drinking water exploitation

Pumping tests are very useful for aquifers characterization especially for exploited ones, but it is even important to provide drinking water without service interruption during tests’ execution. In the Central Italy, the main groundwater resources come from the Apennines carbonate structures which feed the plain and where the main springs can be found. Another important area is the Periadriatic one, where alluvial aquifer can be observed. In this study, three different case studies have been analysed, the first one is the Gran Sasso carbonate aquifer, the largest and most productive in the Apennines (Petitta & Tallini, 2002); its hydrogeological structure has been deeply studied since the middle of the last century for springs’ characterization for drinking purposes and for drilling of a motorway tunnel. The aquifer is characterized by secondary porosity, and an underlying impermeable marly complex, which represents the basal aquiclude. Other tests have been carried out in the Vomano alluvial aquifer and in the Gole di Popoli area. The former is in the Abruzzo Periadriatic area, and it is characterized by gravelly and arenaceous bodies, which work as aquifer, over an aquiclude made by clayey deposits; groundwater is exploited in the portion of the aquifer where the permeable deposits are thicker (Rusi et al., 2004). The second, located in the Apennines area, is a complex aquifer and it can be described as a carbonate aquifer characterized by secondary porosity, under Quaternary deposits referring to alluvial and detrital deposits, marly deposits at the bottom of the permeable succession act as aquiclude (Di Curzio et al., 2018). In carbonate and complex aquifers, 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 this aquifer, the wells’ location, as well as the scarcity of information available and the lack of alternatives forced to estimate some hydrodynamic parameters as in porous aquifers and to test the aquifer experimentally, especially in conditions of maximum pumping even for the evaluation of the influence radius. In all tree, the aquifer testing was performed during the normal activities of abstraction and distribution, it was not possible to perform canonical tests, i.e. with only one pumping well and observing the adjacent wells. Therefore, the step-drawdown test was obtained by turning on an increasing number of wells over time and keeping fixed the observation points. This kind of test, in addition to avoid interrupting the water supply, allowed: – estimating hydraulic conductivity and transmissivity; – estimating drawdown in pumping wells and in observation piezometers in operating conditions; – evaluating the extension of the perturbation induced to the aquifer both at the test and stress discharges; – evaluating flow directions in operating conditions.