A reconstruction of the hydrological record of Lake Ngami, Botswana, since 1849 shows two distinct phases. For the past 100 years Ngami has been a closed-system evaporation lake with a maximum area of 250 km2, prone to periodic desiccation and attendant hardship amongst the local populace. At the time of European expansion into Ngamiland the lake covered an area of 810 km2, at levels slightly below those required to maintain through-flow. The decline of the lake can be attributed to a progressive cessation of inflow in the Thaoge River system due to blockage by papyrus, itself partly attributable to human agencies.