Assessing the Impact of Often Overlooked Snowfall on the Hydrological Balance of Apennine Mountain Aquifers in Central Italy

The accurate knowledge of groundwater availability and its variations is crucial for sustainable groundwater management; in this framework, the water balance is a useful tool to assess the availability of water resources. Currently, the management authority needs a more precise evaluation of groundwater availability to face the rising freshwater demand. In this work, water balance has been determined for the main aquifers in the central Apennines (Italy)—over 2000 km2 wide—and the calculated outflow was compared with springs’ discharge from the data. Inflow data were collected over a 6-year period, from 2018 to 2023, considering both rainfall and snow; the contribution of the snow melting has often been omitted or rarely considered as immediate liquid contribution in the previous works, where usually only liquid inflows from rain have been considered. The snow contribution has been properly evaluated from a recent network of snow gauges and included in the total precipitation for more accurate results. Indeed, for each aquifer, monthly inflow datasets from rain gauges have been interpolated inside the structure using the equations obtained from regression lines and then used for a water balance assessment. An initial comparison of water balances, estimated with and without snow data, demonstrates that neglecting the snow contribution can lead to an underestimation of infiltration values. A comparison between calculated outflows including the snow melt and the measured springs’ discharge has shown a good correspondence for each investigated aquifer.