Pertuso Spring discharge assessment in the Upper Valley of Aniene River (Central Italy)

Sustainable management of karst aquifers is animportant tool for the protection of these strategic water resources. Assessing water balance in a karst aquifer can be very difficult,due to the complex interactions and exchanges between groundwater and surface water. Therefore, measurements of streamflow and spring discharges are useful to assess karst aquifers available budget. Water balance calculation requires the estimation of two main parameters: recharge (precipitation, agriculture water, surface runoff, etc.) and discharge (underground outflow) which are affected by the highly heterogeneous distribution of permeability due to conduits and voids developed by the dissolution of carbonate rocks. This paper deals with the preliminary results of Pertuso Spring groundwater discharge assessment, in the Upper Valley of Aniene River (Central Italy), where the complex hydrogeological characteristics, related to the high heterogeneity of hydraulic properties, make difficult to set up a reliable methodology of measurement. To achieve this objective, an integrated approach based on the streamflow measurements and geochemical modeling, applied to groundwater and surface water was carried out. Because no continuous discharge measurements of Pertuso Spring were available, different methods (velocity–area using current meter and geochemical assessment) were applied to evaluate the discharge of the spring and the stream flow during the monitoring period from July 2014 to May 2015. Aniene River streamflow measurements were carried out by using the conventional current-method and the salt dilution method. For the evaluation of the Pertuso Spring discharge, as a support for traditional discharge methodology, various groundwater and surface water monitoring campaigns have been made along the Aniene River, upstream and downstream the Pertuso Spring, for the acquisition of geochemical data. The aim of this study is to present the preliminary results of an indirect method for the estimation of the Pertuso Spring discharge, based on Magnesium concentration changes in groundwater and surface water.