The snow and rainfall impact on the Verde spring behavior: A statistical approach on hydrodynamic and hydrochemical daily time-series

The wide regional aquifer system springs are one of the most important sources of freshwater, especially because of the ever-increasing global water demand. Thus, these springs must be protected and managed in a sustainablemanner.Tothispurpose,adetailedknowledgeaboutthecorrespondingaquifersystemshydrodynamicisvital. Inthisgeneralframework,theMajellacarbonateaquiferisoneofthemostimportantaswellasheterogenous aquifer systems in Central Italy. It is characterized by high elevation, a heterogeneous hydraulic conductivity distribution and groundwater flow, and its recharge is mainly due to both rainfall and snowmelt. Its mostimportantspringistheVerdespring,locatedintheeasternside,exploitedfordrinkingandhydroelectric purposes. The main objectives of this research are (1) to get a deeper insight into the hydrogeological conceptual model of the Verde spring, combining multiparameter input and output time-series, and (2) to quantify each inflow effect on the Verde spring parameters by a methodological approach that is quite uncommon in literature: comparing univariate and bivariate statistical analyses of both raw and residual (non-systematic component)time-series. The results obtained highlighted that the snowmelt is the most important inflow of the Majella aquifer system.Thesnowcovermeltingleaksslowlylargeamountofwaterintotheaquiferandcreatessmoothlysignificative modifications to the spring discharge, electrical conductivity and temperature, in terms of groundwater volume increase and dilution. Contrariwise, although the rainfall inflow volume and the corresponding spring parameters changes are very limited, the transient behavior of the rainfall inflow allowed identifying different recharge modes. These recharge modes depend on several flow paths in the unsaturated zone, characterized by different water volumes brought toward the saturated zone, sizes, hydraulic conductivities, and distancesfromtheVerdespring