Draft:Groundwater in Guinea Bissau
There is relatively little information on hydrogeology and groundwater potential of the aquifers in Guinea Bissau. The UN report of 1988 describes information from some groundwater reconnaissance projects before 1988.
In the eastern part of the country, the Basement and Palaeozoic Sedimentary (Fracture flow) rocks typically have low permeability and form small and discontinuous aquifers, which are controlled by the distribution, nature and degree of fracturing and weathering. Boreholes must be sited and drilled with great care to locate them in the most productive zones.
In the west of the country, the Cretaceous-Tertiary-Quaternary sequence forms more continuous aquifers. The three main aquifers are:
Maastrichtian sands Palaocene-Eocene (limestone)-Oligocene (sand), and Quaternary sand and laterite. In general, although rainfall is high, evapotranspiration is also high, which may limit the amount of recharge available to aquifers, particularly in the eastern zone. Runoff recharge to the Mesozoic aquifers from adjacent higher ground of the Palaeozoic zones is thought to be significant (UN 1988), although much of the groundwater abstracted from the deeper Mesozoic aquifers may be of fossil origin (UN 1988).