Managed Versus Natural Recharge of Pre-Alpine Phreatic Aquifers

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 m2 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 m3/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.