Structural Classification, Discharge Statistics, and Recession Analysis from the Springs of the Gran Sasso (Italy) Carbonate Aquifer; Comparison with Selected Analogues Worldwide

Abstract

The relative importance of karst conduits and fractures in driving groundwater flow affects the discharge of springs and the long-term availability of water resources. Applying statistics to the hydrographs of the discharge and studying the recessions provide information on the degree of reliability and variability of the springs and, therefore, the flow regime within the saturated part of the carbonate aquifers. This approach was applied to six springs at the Gran Sasso aquifer in Central Italy. These springs were divided into three structural geological groups that determined the position of the permeability thresholds. The type of tectonic structures and the pattern of the permeability thresholds allow a correlation with the computed statistics. The studied springs were associated with the presence of thrusts, overturned drag folds, and a normal fault. The computed statistics describe a general scenario of reliability and steadiness for the springs. The Flow Duration Curves for the springs show limited groundwater flow through the conduits through a comparison with analogues in Slovakia. Joints and bedding plane fractures dominate the groundwater flow, fitting both the relative steadiness of the discharges and the pattern of the Flow Duration Curves. The recessions are also characterized by more gentle slopes with respect to nearby areas fitting a conceptual model of dominant fracture flow. This mathematical scenario depicts groundwater resources, which have limited exposure to episodes of summer droughts. The proposed approach is a holistic combination of structural geology and hydrologic elements and can be successfully exported to other tectonized carbonate areas for the sustainable management of groundwater resources worldwide.