Zimbabwe occupies a tectonically stable plateau underlain by ancient Precambrian crystalline
basement rocks. These form a central craton bounded by east-west trending mobile belts; the Zambezi
mobile belt to the north and the Limpopo mobile belt to the south. Zimbabwe receives generally low
and variable quantities of seasonal rainfall within a semi-arid to savannah type climate characterised
by moderate to high temperatures. Evaporation commonly exceeds rainfall so that recharge to the thin
near surface aquifers is generally low and in some years non-existent. The groundwater resources of
the weathered and fractured basement aquifers that underlie more than 60% of the country are of
limited potential, typically sufficient to supply the needs of small villages and cattle ranches.
However, within the central plateau area of the African to Post-African erosion surfaces, the
weathered and fractured basement may exceed 60 m in thickness. The thickness of this zone
diminishes towards the main valley systems where subsequent cycles of erosion have stripped the
weathered zone away leaving only a shallow surface fractured zone that may only be 20-30 m thick.
Groundwater resources have been developed extensively in Zimbabwe since the 1920s. During the
1991-92 drought abstraction from urban boreholes within the southern Harare area caused yield
decline and ultimate failure of numerous boreholes. It is now time to question the long-term viability
of groundwater development within the basement aquifers in Zimbabwe given the uncertainty in
groundwater resource, the complexities of the climate-groundwater interactions and the projected
demands of a growing rural population.