TITLE:
Conceptual Hydrogeological Model and Groundwater Resource Estimation in a Complex Hydrothermal Area: The Case of the Viterbo Geothermal Area (Central Italy)
AUTHORS:
Antonella Baiocchi, Francesca Lotti, Vincenzo Piscopo
KEYWORDS:
Volcanic Aquifer; Thermal Waters; Overlapping Aquifers Interaction; Viterbo; Italy
JOURNAL NAME:
Journal of Water Resource and Protection,
Vol.4 No.4,
April
17,
2012
ABSTRACT: The conceptual hydrogeological model of the Viterbo thermal area in central Italy and the yield of the groundwater sys- tem have been examined. This area is of great geothermal interest. Through new investigations, three overlapping aquifers have been found. This study examines in detail the two shallower aquifers, characterized by different hydraulic and chemical characteristics. The first aquifer is related to the regional groundwater flow of the Cimino-Vico volcanic system and is generally characterized by cold, fresh waters used for irrigation and drinking water supply. The second aquifer, i.e. the thermal aquifer, supply thermal spas and public pools; it is present where the local hydrostratigraphic, structural and geothermal conditions permit a relatively active flow of higher salinity thermal waters (40?C - 62?C). These two aquifers interact vertically and laterally, giving rise to mixed waters circulating in the first aquifer. The first aquifer is recharged by direct infiltration and inflow from regional groundwater, as well as inflow from the second aquifer. The yield of the thermal aquifer is at least 170 L/s, discharging into thermal springs and wells, besides feeding the shallow aquifer vertically and laterally. Even if a future development of the second aquifer is potentially achievable on a global scale, the exploitation of the thermal waters is strictly dependent on the specific local hydrogeological equilibrium between the overlapping aquifers, different from place to place. The case study highlights that, in the volcanic hydrogeological environment, one of the most stringent constraints in determining the correct usage of a resource is the variable level of interaction of groundwater with different qualities.