Sustainability of yield from wells and boreholes in crystalline basement aquifers

Large areas of the world are underlain by crystalline basement rock of igneous or metamorphic origin (Wright, 1992). For many people in arid and semi-arid regions the groundwater stored in these rocks is the only source of water for long periods of the year. This is particularly true for the rural population without access to piped water. This project was undertaken to investigate the factors that control the yield from wells and boreholes in these aquifers and suggest methods of groundwater development to increase the probability that these yields are sustainable. The project concentrates on the crystalline basement aquifers of Zimbabwe, but many of the _conclusions are applicable to other regions of Africa and the-world. The project-highlighted general issues relating to the sustainability of yield from wells and boreholes as well as producing specific findings with relevance to groundwater development programmes.