The impact of urban development on aquifers in large coastal cities of West Africa: Present status and future challenges

This paper investigates the coastal cities of Abidjan, Cotonou, Lagos and Douala in West Africa. Published data on these areas were aggregated in order to compare the urban development of some African huge cities and assess their impacts on groundwater. Those urban centers have experienced an exponential demographic expansion since the 1950s, with increased population densities and a geographical coverage expansion as well. The Continental Terminal aquifer, major groundwater resource taped in this region by the national water companies and local populations, shows a continuous downward trend in piezometric levels. Concerning water quality, the evolution up to the current state (saline intrusion, nitrate pollution) and the natural geochemical process (dilution, redox reactions) affecting the aquifer have been highlighted. The results confirm the urgent need to consider groundwater development relatively to demographic and economic growth. Some management approaches have been proposed including monitoring of contamination, protection of the resource and the use of shallow large-diameter wells, which have proved to be less saline and more sustainable than deeper small diameter boreholes. The results and discussion of this paper have provided a considerable new insight of West African coastal cities. This will help stakeholders involved in local development to face the urban pressure.