ORIGINAL PAPER Assessment of the effect of a planned marina on groundwater quality in Enfida plain (Tunisia) Mounira Zammouri & Faten Jarraya-Horriche & Bio Oumaro Odo & Sihem Benabdallah Received: 20 August 2012 / Accepted: 21 December 2012 # Saudi Society for Geosciences 2013 Abstract The Enfida aquifer system is of importance to the economic activity of the eastern center of Tunisia. The planning of a marina is likely to present a significant risk on groundwater. Classical physically based modeling is used to better understand salty water intrusion in the aqui- fers. The transport model (MT3DMS) is coupled with the groundwater model (Modflow). Model calibration was car- ried out over the period 1972–2005. Four scenarios were then simulated for a 50-year period, to assess the effects of both planned marina and future abstraction regime. We predict a rise in the groundwater salinity generated by the planned pumping infrastructure. The impact of the planned project will be observed only near the marina. However, limited measurements of transmissivity may affect the mod- el’ s results. Thus, the second part of the paper is aimed to assess the models output error due to the uncertainty in transmissivity, using a stochastic approach. Hundred real- izations of a log-normal random transmissivity field had been performed. According to the most pessimistic realiza- tions, the uncertainty may reach 49 % in the sector of an important pumping field. Accordingly, the calculated con- centration may reach 6.5 g/l in 2055 instead of 3.2 g/l. Keywords Hydrogeology . Groundwater . Flow modeling . Solute transport modeling . Kriging . Uncertainty . Stochastic simulation . Enfida plain Introduction The impact of urbanization may affect water resources in terms of quality and quantity (Appleyard 1995; McAllister et al. 1996; Changming et al. 2001; Lerner 2002; Schiedek et al. 2007; Carlson et al. 2011 etc.). In such situation, modeling is an efficient tool to assist managers and decision makers in assess- ing their impact before implementation. The planning of a marina over an area of 30 km 2 in the coastal zone of Enfida plain, in Tunisia, is likely to deteriorate the plain ecosystem and present significant risk on groundwater. In fact, the planned 20- m depth basin to be dragged on the Mediterranean Sea threaten future water supply in the Enfida plain where groundwater is the most important freshwater resource. The Enfida plain is characterized by a Mediterranean environment where precipi- tation is erratic and moderate. It contains shallow and deep aquifers with variable spatial quality. It is also one of major aquifer in eastern center of Tunisia with regard to its extent and its relevant yield. Renewable resources, estimated to 16× 10 6 m 3 /year, are exploited for irrigation and drinking water supply. The current exploitation, rising to 13.5×10 6 m 3 /year, indicates a strong demand for groundwater, a key resource to economic development in the region. The possibility of sea- water intrusion and consequently of an increase in salinity would lead to direct water supply difficulties. In this paper, a groundwater model, coupled to a transport model, is built in order to study the impact of the planned M. Zammouri Faculté des Sciences de Tunis, Campus Universitaire, Tunis El Manar 2092, Tunisia e-mail: z_mounira@yahoo.fr F. Jarraya-Horriche (*) : S. Benabdallah Centre de Recherches et des Technologies des Eaux, BP 273, Soliman 8020, Tunisia e-mail: faten.jarraya@certe.rnrt.tn S. Benabdallah e-mail: sihem.benabdallah@certe.rnrt.tn B. O. Odo Ecole Supérieure des Ingénieurs de l’Equipement Rural de Medjez el bab, Route du Kef, km 5, 9070, Jendouba, Tunisia e-mail: umarure@yahoo.fr Arab J Geosci DOI 10.1007/s12517-012-0814-0