Water isotope analyses and flow measurements for understanding the stream and meteoric recharge contributions to the Poiano evaporite karst spring in the North Apennines, Italy

The Poiano karst spring is located in the North Apennines (Italy) and it drains Triassic evaporite rocks with a mean discharge of hundreds of liters/second. Two hydrogeological conceptual models have been proposed (and published) for the spring based on tracer tests. Both models highlighted the contribution of the local streams to recharge of the karst aquifer system, through sinking-stream processes, as well as recharge through rainfall; however, those studies differed in the water courses selected to monitor the recharge processes. The aim of the present research is to increase knowledge about the groundwater recharge processes of the Poiano karst spring with new surveys and analyses, resulting in a large dataset of temporal water stable isotope analyses (δ18O, δ2H), temporal stream discharge measurements, and temporal water tritium isotope data (T). A new hydrogeological conceptual model for the Poiano karst spring is proposed, within which a new list of streams becomes involved in the recharge-processes model based on different sources of water. In addition, the research identifies and confirms the occurrence of groundwater flow processes inside the karst system, such as the piston effect.