Assessment of the effect of a planned marina on groundwater quality in Enfida plain (Tunisia)

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 aquifers. The transport model (MT3DMS) is coupled with the groundwater model (Modflow). Model calibration was carried 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 model’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 realizations of a log-normal random transmissivity field had been performed. According to the most pessimistic realizations, the uncertainty may reach 49 % in the sector of an important pumping field. Accordingly, the calculated concentration may reach 6.5 g/l in 2055 instead of 3.2 g/l.