To cope with the general reduction of water availability and increase the subsurface storage of high-quality surficial waters, an artificial recharge project is ongoing in northern Italy within the WARBO LIFE+ Project funded by EU. WARBO is aimed at implementing large-scale use of artificial recharge in Italy where water directives still strongly limit its application. In this context, the Mereto recharge site was selected in the upper Fruili plain where the water availability is guaranteed during winter period by the Tagliamento and Ledra Rivers. An infiltration basin, about 5.5 m deep and 45 × 7 m2 wide, was built at Mereto in the early 2000s but the possibility of implementing the recharge has been allowed only very recently. The site is characterized by an elevation of 105 m asl and the depth to the groundwater table averages 50 m. Below a few meter-thick organic soil, the aquifer is composed by coarse deposits with an estimated thickness of 100 m and an average vertical hydraulic conductivity on the order of 10−4 m/s. A ~0.1 m3/s infiltration flow has been preliminary estimated (corresponding to an infiltration rate of 60 cm/h). Geophysical investigations (electrical resistivity tomography, high-resolution seismic surveys) together with infiltration and pumping tests have been carried out to characterize the vadose zone and the unconfined aquifer in the study area. Functional approaches and three-dimensional (3D) Finite Element numerical computations have been used to predict the effect of the artificial recharge. The results of these investigations will greatly reduce the hydrogeological knowledge gaps and will be used to fine tune the recharge program and to define the monitoring concept. This contribution aims to provide a methodology for the implementation of managed aquifer recharge programs using existing structure

Managed aquifer recharge (MAR) is becoming a common practice worldwide. MAR is carried out in different environments from coastlands to highlands, in megalopolis, farmlands and pristine areas, and in arid and humid regions. Pre-Alpine aquifers represent an optimal target when MAR is aimed at storing large amounts of high-quality waters. In fact, pre-Alpine aquifers are generally characterized by high permeability and a thick unsaturated zone, with the catchments crossed by watercourses rich of high-quality water. Here, we focus the attention to a representative pre-Alpine aquifer system located in the Friuli region, northeastern Italy. A 1-year long MAR test was carried out through a~700 m 2 infiltration basin recharged by water diverted from a nearby channel. The site was characterized from the hydrogeological viewpoint, and the MAR test was monitored through time-lapse hydrogeophysics, water level and piezometric records, and physicochemical water characterization. The data set was used to calibrate a local groundwater flow model, showing that MAR recharged the 50 m deep phreatic aquifer with 1,000 m 3 /day. Hydrogeologic data made available by previous studies were processed to develop a groundwater model of the regional aquifer that allowed for estimating the natural groundwater recharge of the phreatic system and, subsequently, evaluating the MAR effects in the context of the natural balance. If a single MAR site, like the tested one, plays a certain effect at a local scale only, the MAR implementation on several gravel pits and large-diameter wells scattered in the region could store several million cubic meters of water per year, significantly raising the water table and improving the groundwater quality.

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