The Desiccation of Lake Ngami: An Historical Perspective

southern Africa concerns Lake Ngami, at the distal end of the Okavango Delta. When Livingstone and his companions first visited the north-east end of the lake on 1 August 1849 they beheld a 'fine-looking sheet of water' (Livingstone, 1858a : 75), yet the lake bed at present is dry, and has been so on a number of occasions during this century. The apparent diminution of the lake inferred from the observations of Victorian travellers led, by the the early twentieth century, to a popular belief in the progressive desiccation of the northern Kalahari within the span of human experience, an idea derived from Livingstone (1858b), which reached its zenith in the grandiose schemes of Professor Schwarz (1920) to refill 'Greater Ngami' and thereby alter the climate of southern Africa. Public interest in these schemes led to a series of investigations into their practicality; indeed into the possibilities of large-scale water use in the Okavango as a whole (Du Toit, 1926; Jeffares, 1938; Mackenzie, 1946; Kokot, 1948; Brind, 1955). All of these studies, to a greater or lesser extent, looked into the diminution of Lake Ngami on the basis of historical evidence, with little reference to the geomorphology of the basin itself. The results were as ambiguous and inconclusive as the very observations of the travellers themselves, though clearly the 1850s and 1860s were a period in which the hydrology of the western Okavango system was undergoing change. This paper attempts to establish the palaeohydrology of Lake Ngami for the past 150 years, with particular reference to the size of the nineteenth-century lake and its subsequent fluctuations. It is based on historical sources, recent geomorphological investigations, and, for the last three decades, available remote-sensing data.