Hydrogeology of thermal waters in Viterbo area, central Italy

Abstract

A conceptual hydrogeological model of the Viterbo thermal area (central Italy) has been developed. Though numerous studies have been conducted on its geological, geochemical and geothermal features, there is no generalized picture defining the origin and yield of the hydrothermal system. These latter aspects have therefore become the objectives of this research, which is based on new hydrogeological and geochemical investigations. The geological setting results in the coexistence of overlapped interacting aquifers. The shallow volcanic aquifer, characterized by fresh waters, is fed from the area around the Cimini Mountains and is limited at its base by the semiconfining marly-calcareous-arenaceous complex and low-permeability clays. To the west of Viterbo, vertical upflows of thermal waters of the sulphate-chloridealkaline- earth type with higher gas contents, are due to the locally uplifted carbonate reservoir, the reduced thickness of the semiconfining layer and the high local geothermal gradient. The hot waters (30–60°C) are the result of deep circulation within the carbonate rocks (0.5–1.8 km) and have the same recharge area as the volcanic aquifer. The upward flow in the Viterbo thermal area is at least 0.1 m3/s. This flow feeds springs and deep wells, also recharging the volcanic aquifer from below

An Integrated Approach to Identify Water Resources for Human Consumption in an Area Affected by High Natural Arsenic Content

“…These waters are considered to be due to rising of deeper groundwater through circuits into the sedimentary basement of the volcanics, where the basement is locally uplifted, fractured, and faulted, and a strong heat flow anomaly exists. The yield of these deeper groundwater circuits for the hydrothermal area of Viterbo is at least 0.1 m 3 /s [36][37][38]. The hydrogeological conceptual model described above is summarized in Figure 3, where the different flow paths are schematically shown.…”

“…Chemical characteristics of groundwater are coherent with this hydrogeological model. Thermal waters are of the sulfate alkaline earth type, have temperatures between 40 °C and 62 °C, electrical conductivity between 2700 μS/cm and 3400 μS/cm, tritium concentrations between 2 TU and 5 TU, and high gas content, e.g., CO2 and H2S up to 994 mmol/mol and 0.99 mmol/mol in dry gas, respectively [36][37][38][39]. In contrast, the waters of the perched and basal aquifers comprise fresh, cold waters of the bicarbonate alkaline earth type (electrical conductivity generally between 100 μS/cm and 1000 μS/cm, temperature generally between 13 °C and 20 °C, tritium concentrations between 8 TU and 11 TU).…”

“…In contrast, the waters of the perched and basal aquifers comprise fresh, cold waters of the bicarbonate alkaline earth type (electrical conductivity generally between 100 μS/cm and 1000 μS/cm, temperature generally between 13 °C and 20 °C, tritium concentrations between 8 TU and 11 TU). In the hydrothermal area of Viterbo, the reduced thickness of the low-permeability layer that divides the basal aquifer from the deeper aquifer and its hydraulic heterogeneity give rise to a flow between the two overlapping aquifers and then to mixing between cold and thermal waters [17,[36][37][38][39]. All waters exhibit …”

Conceptual model of the Şavşat (Artvin/NE Turkey) Geothermal Field developed with hydrogeochemical, isotopic, and geophysical studies

“…The 34 S CDT value (~ 10‰) shows that the sulfur in the geothermal water is derived from volcanic sulfur (SO 2 ). which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.hydrogeochemical and isotope techniques have been widely used elsewhere to determine the hydrodynamic structure of geothermal systems in recent years (Tarcan et al 2005;Piscopo et al 2006; Schaffer and Sass 2014; Yurteri and Şimşek 2017;Uzelli et al 2017). In this geothermal field, there has not been any study that employs a conceptual approach based on hydrogeological and hydrogeochemical studies, such as hydrochemical facies compositions, isotopic features, water-rock interactions, mixing processes, and reservoir temperature.…”

“…hydrogeochemical and isotope techniques have been widely used elsewhere to determine the hydrodynamic structure of geothermal systems in recent years (Tarcan et al 2005;Piscopo et al 2006; Schaffer and Sass 2014; Yurteri and Şimşek 2017;Uzelli et al 2017). In this geothermal field, there has not been any study that employs a conceptual approach based on hydrogeological and hydrogeochemical studies, such as hydrochemical facies compositions, isotopic features, water-rock interactions, mixing processes, and reservoir temperature.…”