Hydrogeology of basement

Crystalline basement rocks cover approximately 34% of African land mass, much of it which is highly populated. The hydrogeology is complex with groundwater occurring in the weathered and fractured parts of the rock, which can often support low yielding boreholes, suitable for hand pumps or maybe lower yielding solar powered pumps. Intriguingly, higher yielding boreholes supporting well fields and municipal supply can also sometimes be found. In this talk I will explore how a domains approach can help reduce uncertainty in mapping potential yield from boreholes. I will use lithology, geological and climate history to help explain continental variations in permeability, and develop a stochastic model for likely yields in areas. A similar approach is then taken to mapping variations in a catchment, and applied to separate catchments in basements areas in Africa and India, with a particular emphasis on the potential for weathering and fractures.