This report describes the methodology, and results of the West Africa hydrogeological case study, undertaken within the one-year project. Groundwater residence times were assessed in both high and low storage aquifers across 4 different climate zones in a sampling transect from southern Nigeria to central Mali. Groundwater residence times were assessed through the use of multiple tracers: chlorofluorocarbons (CFCs), sulphur hexafluoride and tritium. The purpose of the case study was to identify how vulnerable rural water supplies may be to climate change.
Detailed sampling in West Africa from hand-pumped boreholes abstracting shallow (less than 50 m deep) groundwater indicates significant resilience to climate variability across the range of climate zones sampled (mean annual rainfall 400–2000 mm). The mean residence of groundwater in shallow aquifers was approximately 20–70 years and therefore well buffered against short term variations in climate.
Lapworth, D. J.; MacDonald, A. M.; Darling, W. G.; Gooddy, D. C.; Bonsor, H. C. Case study note: Groundwater residence times for rural groundwater supplies across different climate zones, West Africa. British Geological Survey, Nottingham, UK (2010) 22 pp. [British Geological Survey Internal Report IR/10/100]