Deeply weathered rock, often tens of metres in thickness, forms a 'blanket' that overlies granite, gneiss and other crystalline bedrock formations throughout tropical and sub-tropical regions including Africa, Asia and the Americas. Groundwater flowing through weathered rock, sometimes referred to as 'regolith' or 'saprolite', is able to provide significant well yields and, in many places, is the only source of potable water supply that is available to rural communities. Aquifers within mantles of deeply weathered crystalline rock are, however, neither well understood nor well utilized. This paper describes both the evolution and basic characteristics of these aquifers and highlights the potential for improved development of this resource by rural communities.
In sub-Saharan Africa, projected increases in the development of groundwater and pollutant discharges to the subsurface will inevitably magnify the risk of degrading the quality and quantity of available groundwater resources. Groundwater protection will consequently prove an essential component of efforts to develop groundwater resources sustainably in this region.