Hydrological deformation of karst aquifers detected by GPS measurements, Matese massif, Italy

We used hydrological and geodetic observations to characterize the effects of hydrological forcing on the displacements observed by GPS (Global Positioning System) measurements collected by stations located in the karst area of the Matese massif (Apennines, central-southern Italy). The latter is one of the main karst massifs of the central-southern Apennines, characterized by steep slopes, high mountain peaks (up to 2050 m a.s.l.), and wide endorheic areas, playing a fundamental role in recharging the large groundwater resource of the massif. Integrated statistical analysis of rainfall and spring discharge time series provided insight into timescales characterizing the hydrological dynamic of the Matese massif, highlighting how hydraulic conditions of the water table at a specific time mainly depend on long antecedent periods of rainfall. Nevertheless, the intense daily rainfall occurring during the wet season is responsible for the abrupt increase of the discharge of the Matese's springs, which show a typical karst behavior. Statistical analyses of time series show robust correlations between hydrological conditions of the karst aquifer and GPS displacements observed at stations placed over and around the massif. We find that the observed outward and inward deformations of the massif (horizontal dilatation and contraction) are controlled by the water table variations, which are in turn controlled by the temporal variations of the groundwater recharge due to rainfall. The detected deformation patterns are intimately related to the seasonal and multi-year characteristics of the recharge/discharge processes and allowed us to track with geodetic measurements the different phases of the water cycle in the karst aquifer of the Matese massif.