## 6 Conclusions  
The San Vittorino Plain, an intramontane plain where a large amount of groundwater resources converges from large mountain fractured aquifers to several springs affected by different degrees of mineralization, represents one of the more interesting areas for evaluating groundwater mixing of direct rainfall recharge components with deep fluids uprising along high-angle faults reaching a depth of at least 5 km b.s.l. In our study, we suggest a methodological approach useful for improving groundwater monitoring aimed at identifying geochemical signals related to crustal deformation and potentially to seismic activity. Analysis of the results of major and trace elements, stable isotopes of water, chemistry and isotopes of dissolved and free gases, coupled with an updated geo-structural setting and very detailed knowledge of the hydrogeology, allowed us to build a robust conceptual model where all elements converge into a coherent framework. By applying different geothermometers, a reliable thermodynamic balance reveals the Na-Li geothermometer as an affordable tool for calculating the equilibrium temperature of the deep contributions, established at approximately 150-200 \({}^{\circ}\)C. Such deep fluids show a hydrogen and oxygen isotope composition typical of meteoric water, whereas the \({}^{18}\)O-enriched component typical of high-temperature magmatic fluids is substantially absent. However, the analysis of He and CO\({}_{2}\) isotopes confirms the presence of a deep component with possible traces of mantle-derived helium (1-2%). Trace element occurrence clarifies the water-rock interaction processes and supports the conceptual model based on the localized uprising of deep fluids that do not casually match the distribution of high-angle faults that are capable of connecting different reservoirs delimited by less permeable thrust zones. The distribution and concentration of deep fluids uprising and spreading into the aquifers cause significant changes in the classical calcium-bicarbonate equilibrium of the basal springs, allowing the subdivision of the sampled selected springs into three groups showing different degrees of deep contribution (G1, G2, and G3). On the basis of the reviewed structural map, the geological setting shown in the cross-sections presented herein could also make possible the uprising of deep-derived gases in the Velino Valley. In this sketched model, it is now clear that these high-angle faults work as a network of pathways through which deep fluids reach the shallow regional aquifers that are otherwise totally recharged by meteoric infiltration. Based on geothermometrical analysis and structural cross sections, we inferred the origin of the deep fluid portion at a depth of approximately 7-10 km, where Apennine earthquakes usually occur. Consequently, this integrated approach can help identify the most suitable sites aimed at analyzing the relationships between groundwater and seismicity. Indeed, knowing the mixing degree among different springs, it is possible to recognize whether and where the flux of the deep portion, modulated by fault activity, increases or decreases with respect to permeability variations along the uprising zones. A list of possible criteria found within this study for the optimization of future groundwater hydrogeochemical monitoring aimed at correlating crustal deformation along faults and related (micro- and perhaps macro-) seismicity can be summarized as follows: (a) discharge areas with concentrations of different hydrochemical spring characteristics; (b) steady base flow from regional aquifers recharged by meteoric infiltration; (c) selection of the most representative sampling sites on the basis of a complete hydrochemical/isotopic analysis; and (d) review of fault geometries at the surface and depth. We consider the future possible establishment of a groundwater monitoring network based on the abovementioned criteria to be very useful for improving the contribution of groundwater monitoring to the wide research field of earthquake precursors.