Hydrogeological features of high-altitude springs of the Cambio Mt. hydrostructure (Rieti, Italy) and local meteo-climatic effects on their discharge processes

Abstract

This work is aimed at the hydrostructural characterisation of a portion of the Mt. Cambio aquifer system (eastern Reatini Mountains) and the hydrodynamic study of perennial suspended springs for which time series data on discharge are available.The outcropping lithotypes belong to the Umbro-Marchigiano- Sabina Succession (pelagic basin sediments, mainly negrained and well-stratified), inter ngered with detritic ows. A synform structure was identi ed, including associated undulations, minor folds and normal faults. More important normal faults delimit the aquifer, hosted in a succession ranging from the Corniola to Maiolica Formations, placing this succession in contact with the Calcare Massiccio Formation.An attempt was made to calculate the hydrogeological budget for the hydrostructure, detecting an effective in ltration surplus of 600-750 mm/yr (40-50 l/s of groundwater resource). This resource is probably directed towards the regional basal aquifer and/or towards other adjoining aquifer systems.Taking into account the Thornthwaite empirical formula and considering the temperature time series, two distinct models (referred to both the rst and the last years of the series) for the monthly potential evapotranspiration were obtained and compared. Furthermore, both the time lag from the precipitation events to the corresponding increasing of the spring ow and the memory effect of the local hydrodynamic system were estimated. These results were also compared with the literature information regarding other signi cant springs.The cross-correlation analysis among the ow time series of some perched springs of the Mt. Cambio hydrostructure and of the basal spring of S. Angelo (Mt. Terminillo hydrostructure) has been conducted in order to evidence possible differences among their feedback time to a same pluviometric event, likely re ecting the different hydrostructural settings.The recession coef cients of some springs of the Monte Cambio hydrostructure have also been calculated.The obtained information allowed us to describe the geological and hydrostructural features of the M. Cambio aquifer in the frame of the calcareousmarly Meso-Cenozoic succession of the Umbro-Marchean-Sabino Apennines, also considering the results derived from the study of both the spring flow time series at different time scales and the correlated local climatic evolutionary processes.