Dry fossil valleys (mekgacha) are an important landscape feature in the semi-arid to arid Kalahari Desert of central southern Africa. The majority of valleys do not contain flow, except in their headwater regions, but may contain pools of water on a seasonal basis. As a result, they are frequently mentioned in historical accounts of the region recorded by European travellers, and from these reports it is possible to assemble a picture of hydrological change. Keywords: Kalahari, dry valleys, documentary evidence, environmental change.