Numerical modeling to estimate the artesianism evolution in North-Western Sahara Aquifer System

Abstract

This paper presents the latest results obtained by a numerical model of the groundwater circulation in the North Western Sahara Aquifer System (NWSAS). The aim was to obtain some realistic simulations of the piezometric downward trend and the decrease of local artesianism.
On the basis of the experience acquired in the last few years in the framework of an intergovernmental cooperation project, it was possible to use a recent regional numerical model developed by the South Sahara Observatory. This model was used to set up a new local model for the Tunisian Chotts region in order to implement different plausible scenarios for the exploitation of the underground water resources. The local numerical model covers an area of about 30000 Km2, including part of the Algerian territory close to the boundary with Tunisia and the whole Chott el Djerid region in South Tunisia.
Adjusting the regional model for the local modeling study required using the data gathered during the 2007 ad-hoc survey focused on the piezometric monitoring of some artesian wells and on several output measurements.
The assumptions on the possible evolution of withdrawals in this area allowed for developing16 different exploitation scenarios to be implemented in the local model.
The simulations showed a piezometric decline ranging between 0.8 and 1.2 m/a and the disappearance of local artesianism between 2015 and 2035 horizon.