ABSTRACT
ABSTRACT: The domestic water supply of Abidjan depends on groundwater abstracted from local sandy aquifer formations. The quality and quantity of this resource are threatened by surface activities and population growth, caused partly by war, which resulted in a rapid and massive displacement of populations towards Abidjan. This displacement of the population exerts an enormous pressure on groundwater resources. This study uses a numerical groundwater flow model to quantify the available groundwater resources of the Abidjan aquifer and to assess the risks associated with the presence of potential polluting activities. The conceptual hydrogeological model comprises two sand layers overlying a presumed impervious rock formation and the lateral limits of the aquifer are physical water bodies such as rivers and the Atlantic Ocean. The hydrogeological parameters of the aquifer were determined from previous studies. The aquifer recharge is provided by the river leakage and rainfall which has been computed by a water balance calculation. The numerical model was built using MODFLOW and calibrated in steady-state flow with initial groundwater head measurements from 1978 and then validated in transient flow with piezometric data from 1992 and 2005. Predictive simulations in transient flow with projected groundwater withdrawal from 2005 to 2030 were carried out. In order to define protection areas of this aquifer, the wells capture zones were calculated using MODPATH. The results indicate that the Abidjan aquifer can be used for future groundwater supply and the methods employed can help to manage and protect the aquifer.
