Sustainability assessment of groundwater exploitation based on hydrogeological and hydrogeochemical studies: the case study of the Venafro Mountains (Southern Italy)

The Venafro Mountains represent a well-defined carbonate unit, bounded to the north by the valleys of the Mollarino River and the Acquoso River, to the south by the slopes of the Roccamonfina volcano, and to the east and west by the plains of Venafro and Cassino, respectively. The eastern sector of this mountainous system, west of the town of Venafro, hosts significant groundwater resources tapped by the Aqueduct of Western Campania. These include the Campopino tunnel, housing a drainage section (Sammucro, ~160 L/s) and a wellfield constituted of 19 drillings with a total average flow rate of about 1000 L/s. The groundwater intercepted by these structures continues its flow southward, feeding the Peccia springs (~5000 L/s), about 7 km away. In this area, the groundwater exhibits a particular mineralisation with respect to other sectors, whose origin was investigated in detail. The chemical composition of the waters intercepted in the Sammucro area and in the wellfield are of bicarbonate-calcium type, with average characteristics of TDS = 321 mg/L, CO2 = 69 mg/L, and hardness = 25.5 °F. Also the Peccia springs are bicarbonate-calcium but, compared to the previous waters, show higher mineralisation and CO2 content, with average values of TDS = 714 mg/L, CO2 = 320 mg/L, and hardness = 63.6 °F. In the town of Venafro, there is another Aqueduct tunnel related to the S. Bartolomeo spring (~1100 L/s). The northernmost spring in the examined area (Capo d'Acqua) is located in the Pozzilli area (about 8 km north of Venafro) and has a flow rate (~500 L/s) partly used within the Consortium for Industrial Development Isernia-Venafro. In this study, numerous data (climatic, chemical, isotopic, etc.) were collected and analysed to assess the sustainability of the current groundwater use with respect to the annual natural recharge. Beyond the evaluation of the natural recharge, the analysis of the withdrawals and their effects on the water levels of the Venafro plain aquifer (adjacent to the reliefs and fed by underground outflow) was performed. For this purpose, more than 40 wells in the Venafro plain were surveyed, measured, and georeferenced.