Combining water isotope analyses and lumped parameter modelling to detect the functioning of a carbonate aquifer in a mountain range

Hydrogeological studies with a focus on the cryosphere became numerous during the last years due to the sensitivity of snowfalls to the climate variations. This study investigated the Gran Sasso Range in central Italy, which is a carbonate mountain characterized by rainfalls and snowfalls. A study of stable water isotopes (δ 2 H and δ 18 O) of rainfall, snow, ephemeral and perennial streams and groundwater is proposed to constrain the principal processes involved in the aquifer recharge. These results were considered to set up a conceptual model of functioning, that was tested with the KarstMod modelling platform. The snow represents a significant component of the recharge as shown by a comparison of the water isotopes that indicate superimposition in δ 2 H, δ 18 O diagrams between snow, ephemeral streams derived by the snowmelt, perennial streams and groundwater. The Campo Imperatore Plain receives significant snow coverage during the winter and represents the main recharge area in agreement with stable isotopes. Based on this scenario, a lumped parameter model that incorporates a snow-routine was defined to simulate spring discharge with Campo Imperatore as upper reservoir, and two lower reservoirs representative of fractures and conduits. The numerical model shows that groundwater is recharged by snow (49%) and rain (51%).