ABSTRACT
ABSTRACT: Three-dimensional modelling of groundwater flow was carried out for the coastal aquifer system of Godomey (Benin, Western Africa), in order to determine the probable sources of salt-water intrusion in an area of intensive pumping. The model, under the assumption of steady-state with mean abstraction rates recorded over the period 19912000, was used to investigate the impact of current levels of abstraction (as of 2000) as well as the likely impact of a predicted increase in pumping to occur by the year 2011. The simulation results indicate that salt-water intrusion under current conditions comes only from Nokoué Lake, a shallow, salt-water lake. When a higher production rate was modelled (for the year 2011, again under the assumption of steady-state), it was observed that the potential for salt-water intrusion increases significantly, now including potential for intrusion not only from the lake, but also from recharge related to salt-water lagoons along the coast and possible salt-water upflow derived from deeper aquifers within the system. By taking into account the results of the model, an initial management strategy was developed to limit salt-water intrusion. These results are considered only as preliminary because of the assumptions of steady-flow and neutral density. Therefore management strategies are an interim measure during the period required to develop a more sophisticated management model that will include transient flow and density effects.
