Application of the MRC method to the study of some mountain springs in the Tennacola stream catchment (central Apennine, Italy)

The mountain portion of the Tennacola stream basin, located in the north-east sector of the Sibillini Mountains (Central Apennines, Italy), is characterized by the presence of numerous springs, exploited for drinking purpose. The presence of lithotypes with different permeability, allowed the formation of three main hydrogeological complexes, overlapped and characterized by two groups of springs with different discharge and regime: - the Group of springs Tennacola “high”, located in the uppermost portion of the catchment, at altitudes between 1100 m and 1150 m a.s.l. and with mean annual discharge of about 30l/s; - the Group of springs Tennacola “low”, the most important resources of the area with discharge ranging between 70 and 200 l/s, placed at different elevation between 800m and 700 m a.s.l. The hydrogeological regime of the springs has been defined applying (for the first time to Apennine aquifers and particularly to springs with discharge < 100 l/s) the methodology of the Master Recession Curves: the method, simultaneously analyzing the recession curves of several years, allows to evaluate the hydrogeological features of a groundwater reservoirs and to integrate the results obtained from a single spring hydrographs analysis. In particular, the value and the trend obtained for the depletion constant α evidenced that the groundwater circulation can generally be associated with the presence of a diffuse fracturing, medium-low opening of joint systems and low permeability matrix, with consequent higher storage and gradual and constant release of water; the presence of conduits and pipes associated with typical karst systems can therefore be ruled out. The results, confirming the applicability of the method also to minor springs, are therefore encouraging and push to a growing commitment in this direction.