Three-dimensional hydrogeological reconstruction based on geological depositional model: A case study from the coastal plain of Arborea (Sardinia, Italy) Giorgio Ghiglieri a,b, ⁎, Alberto Carletti a,b , Stefania Da Pelo a , Fabrizio Cocco a , Antonio Funedda a , Alfredo Loi a , Fabio Manta a , Daniele Pittalis b,c a Department of Chemical and Geological Sciences, University of Cagliari, Via Trentino 51, 09127 Cagliari, Italy b Desertification Research Centre (NRD), University of Sassari, Viale Italia, 07100 Sassari, Italy c Department of Physics and Earth Sciences, University of Parma, Parco Area delle Scienze 157a, 43124 Parma, Italy abstract article info Article history: Received 13 October 2015 Received in revised form 4 April 2016 Accepted 15 April 2016 Available online 19 April 2016 This study presents a novel approach for the hydrogeological assessment of sedimentary coastal aquifers. Specifical- ly, the methodology is tailored for modeling groundwater flow and nitrates contamination in typical Mediterranean coastal plains with high anthropogenic pressures, as exemplified by the Arborea plain (central western Sardinia, Italy). The study started with development of an updated geological–depositional model based on sequential stra- tigraphy. Geological and geophysical data, processed in a geographic information system (GIS) environment, sup- ported the definition of a 3D hydrogeological conceptual model and provided a solid basis for the interpretation of groundwater flow directions. The 3D hydrogeological model allowed constraining groundwater circulation, flow paths and distribution of nitrate concentrations in the aquifers. The methodology appears as a valid tool appli- cable in other coastal areas to determine geological and hydrogeological settings. The definition of a quantitative hydrogeological framework will support the effective management of local water resources. © 2016 Elsevier B.V. All rights reserved. Keywords: 3D hydrogeological–conceptual model Groundwater Nitrate pollution Nitrate Vulnerable Zone Desertification Sardinia 1. Introduction The contamination by nitrate (NO 3 - ) of groundwater is becoming a ubiquitous problem. The World Health Organization has recommended a threshold of 50 mg L -1 in drinking water (WHO, 2003), but ground- water concentrations in Europe commonly exceed this level in 22% of cultivated land (Sacco et al., 2007), and similar concentrations occur in arable areas of the USA (Canter, 1997). The concern about the potential pollution of groundwater because of increasing human pressure on the environment has led to the development of an extensive legal frame- work. Both the 91/676 and 2006/118 Directives, issued by European Commission respectively for the protection of waters from nitrates of agricultural origin and for the protection of groundwater against pollu- tion and deterioration (Groundwater Directive — GWD), have been im- plemented in Italy. Nitrates Directive states that all areas of land which drain into waters exceeding the concentration of 50 mg L -1 of NO 3 and which contribute to nitrate pollution must be designated as “Nitrate Vulnerable Zones” (NVZs). In these areas, farmers are required to com- ply with specific measures directed to improve water quality. Although the Directive clearly states the criteria for identifying NVZs, the imple- mentation of these criteria has varied from country to country. The des- ignation of an NVZ must take into account all relevant physical and environmental factors (i.e. aquifer characteristics, flows and solute transport in the saturated zone, the behavior of nitrogen compounds in the environment and land use) that may influence the nitrogen dynamics. Many NVZs worldwide are located in flat lands and in coastal areas where the intense agricultural activity, the high concentration of inhab- itants and the seasonal population determine a significant water de- mand. In those areas, several environmental concerns may occur at the same time. Indeed, in farmed coastal zones the impacts on water re- sources include pollution due to nutrient and pesticide leaching and seawater intrusion into aquifers (Steinich et al., 1998; Zalidis et al., 2002; Ghiglieri et al., 2012). Groundwater management in coastal aqui- fers requires the elaboration of a local geological and hydrogeological conceptual model in order to understand the processes determining the quality of water, the hydrodynamic parameters and the productivity of aquifers. During the last few years, techniques in 3D hydrogeological model reconstruction/visualization have been improved (Wu et al., 2005; Jones et al., 2009; Wycisk et al., 2009; Best and Lewis, 2010; Cox et al., Engineering Geology 207 (2016) 103–114 ⁎ Corresponding author at: Department of Chemical and Geological Sciences, University of Cagliari, Via Trentino 51, 09127 Cagliari, Italy. E-mail addresses: ghiglieri@unica.it (G. Ghiglieri), acarletti@uniss.it (A. Carletti), sdapelo@unica.it (S. Da Pelo), fabrcocco@gmail.com (F. Cocco), afunedda@unica.it (A. Funedda), alfloi@unica.it (A. Loi), fabio.mantax@gmail.com (F. Manta), daniele.pittalis@unipr.it (D. Pittalis). http://dx.doi.org/10.1016/j.enggeo.2016.04.014 0013-7952/© 2016 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Engineering Geology journal homepage: www.elsevier.com/locate/enggeo