Springs monitoring data analysis with a frequency and time domain approach: The case study of Mascognaz spring (Aosta Valley)

Aquifers in mountain areas are a strategic resource for people who live there. In fact, their proper management is strongly influenced by periods of high water stress, linked to tourism activity. In order to optimize future water management, it is fundamental to understand hydrogeological characteristics of these systems. Due to the lack of economic resources, these hydrogeological systems are investigated with a very low level of detail. In fact, usually, there are very few borehole permitting hydrogeological characterization of groundwater systems. In great part, therefore, studies on the functioning and hydrodynamics of aquifers have been based on analyzing the hydrograph behavior (depletion and/or recession) or on the complete hydrograph, corresponding to an identifiable rainfall event. The aim of this paper is to apply time series analysis in time and frequency domain, in order to enable the study of the whole hydrographs of mountain springs and their relationship with the input function (precipitation essentially). This approach is opposed to many other methods that limit the analysis at the recession or another part of the hydrograph. The application of these techniques to the case study of Mascognaz spring, located in the North-Western Alps in the Aosta Valley Region (Italy), helped to obtain useful information about the effects of external phenomena on the spring's hydrograph. Moreover, the applications of time series analysis permits to establish the flow type, that characterizes the spring. In this case study, the prevalence of components of flow base-flow is highlighted and the underground system shows similar characteristics of a porous medium.