Potential Impact of Climate Change on Ground Water Quality in the Godomey Aquifer System, Benin, West Africa: Initial Considerations

Ground water wells within the Godomey aquifer system supports the domestic water supply for Cotonou, Benin.  At present, this aquifer system represents the sole source of domestic water supply for this city of over 1.5 million people.  A relatively complex sequence of sediments, this aquifer system shows initial indications of intrusion of surface contaminants through intrusion of saline waters from the Atlantic Ocean and Lake Nokoue (a salt water lake bordering Cotonou).  Numerical modeling and field characterization of this system indicate that coastal marshes and Lake Nokoue are both critical hydrologic features in groundwater recharge and, therefore, in potential intrusion of saline or otherwise contaminated recharge.   Further, field characterization demonstrates that the coastal marshes are complex, with both spatial and temporal variation in recharge versus discharge of ground water.  Changing climate may lead to several potentially dramatic changes to this aquifer system.  These include substantial changes in the hydraulics and water quality of the southern marsh areas, changes in water level and water quality in Lake Nokoue, and increased significance of a coastal freshwater river system feeding Lake Nokoue.