1 Driving the modeling of saltwater intrusion at the Venice coastland (Italy) by ground-based, water-, and air-borne geophysical investigations P. Teatini 1 , L. Tosi 2 , A. Viezzoli 3 , R. de Franco 4 , G. Biella 4 , C. Tang 5 1 Department of Mathematical Methods and Models for Scientific Applications, University of Padova, Via Trieste 63, 35121 Padova, Italy; PH (39) 049-8271330; email: teatini@dmsa.unipd.it 2 Institute of Marine Sciences, National Research Council, Castello 1364/A, 30122 Venezia, Italy; PH (39) 340-4859413; email: luigi.tosi@ismar.cnr.it 3 Aarhus Geophysics APS, Hoegh-Guldbergs Gade 2, Aarhus DK-8000, Denmark; PH (45) 4696-3932; email: andrea.viezzoli@aarhusgeo.com 4 Istituto per la Dinamica dei Processi Ambientali, National Research Council, Via Mario Bianco 9, 20131 Milano, Italy; PH (39) 02-28311442; email: roberto.defranco@idpa.cnr.it , gaincarlo.biella@idpa.cnr.it 5 Yantai Institute of Coastal Zone Research for Sustainable Development, Chinese Academy of Science, Chunhui Road 17, Laishan Districy, 264003 Yantay, China; PH (86) 535-2109021; email: ctang@yic.ac.cn ABSTRACT The coastland surrounding the southern Venice Lagoon, Italy, is a precarious environment subject to both natural changes and anthropogenic pressure. One major environmental problem is the saltwater contamination in shallow aquifers. Since the early 2000s, a significant effort has been devoted to understand the process dynamics by integrating different geophysical techniques, i.e. TL-ERT (Time Lapse - Earth Resistivity Tomography), MRT (Marine RT), AEM (Airborne ElectroMagnetic), and shallow water VHRS (Very High Resolution Seismic) surveys. The monitoring results have been used to drive the development of a reliable numerical model for the simulation of the saltwater intrusion along the margin of the southern Venice Lagoon. The model solves the coupled density dependent flow and transport equations by a highly accurate numerical approach based on the mixed hybrid finite element (MHFE) method and a combination of MHFE with high resolution finite volumes (HRFV) for the discretization of the flow and transport equations, respectively. Modeling application provides a clear picture of the relative importance of the factors that contribute to the soil contamination in the study area. INTRODUCTION Groundwater/seawater exchange in coastal areas impacts both onshore and offshore the quality of water resources through saltwater intrusion into water-supply aquifers and the discharge of contaminated groundwater into the coastal sea. Saltwater intrusion represents a threat to drinking water quality (Qahman and Larabi, 1146 World Environmental and Water Resources Congress 2010: Challenges of Change. © 2010 ASCE