Hydrogeochemistry and Isotopic Composition of Waters in the Renella Cave (Central Italy): New Insights into Groundwater Dynamics

This article presents data from monthly monitoring carried out on cave and stream waters belonging to the Renella Cave karst system from September 2020 to April 2022. Additionally, old data pertaining to cave waters from previous published work are discussed. The aim is to develop a dataset for future climatic and hydrological studies on the Renella Cave and its surface recharges. Water samples were collected and analyzed for major ions, δ18O and δ2H, on water molecules. The cave sump water level, water temperature, and electrical conductivity were continuously measured and compared to the precipitation data. Additionally, air temperature and pressure inside and outside the cave were also monitored. The classification based on the Piper-Hill diagram indicated that both stream and cave waters belong to the bicarbonate-alkaline earth hydrochemical facies, indicating that their chemism is essentially determined by the dissolution of the Grezzoni Fm. Isotopic data suggest that both stream and cave waters have a meteoric origin, and their variability mainly depends on underground homogenization. Hydrogeochemistry, isotopic composition, and the monitoring data allowed a deeper understanding of the cave karst system, and identified an underground circulation network that is fragmented into independent parts.