Hydrogeological scheme and steady state flow model of the Vico Lake basin

1 !"#$%&'(#!%") The present work deals with a detailed hydrogeological study of the Lake Vico basin, enhanced by the implementation of a groundwater numerical model. In 2009, the Lake Vico basin was declared to hold two different regional contaminated sites (Regione Lazio, 2012). The first involves the sediments at the bottom of the lake, where anomalous concentrations of Arsenic, Cadmium and Nichel where found; the second consists of a dismissed military zone for the manufacture of chemical weapons during the II World War. In addition to this, the water tapped for drinkable and irrigation purposes contains high concentration of arsenic, consequences of the volcanic origin of lake, and a toxic microcistyn (Plankhotrix rebescens) due to the lake eutrophication (Leone and Marini, 1993; Bruno et al., 2012). This work is part of a larger project, involving different local Authorities and research Institutions, aimed to the characterization of the two contaminated sites of the Lake. The first step consisted in updated and detailed geological and hydrogeological investigations to define the surface - groundwater relationships and the groundwater flow domain. Secondly, a numerical flow model was implemented in order to provide an effective management tool to the authorities in charge of the monitoring of this fragile environment. Lake Vico is situated in the North of Lazio Region, in the province of Viterbo (Fig. 1.1). It belongs to the Roman comagmatic province together with Bolsena, Bracciano, Martignano, Monterosi, Nemi and Albano lakes. The study area, with its extension of 250 km 2 , comprises the Cimino and Vico volcanic complexes. The hydrological basin of Lake Vico is approximately 40 km 2 , 12 km 2 of which are covered by the lake with an average elevation of 620 m a.s.l.