Ngami

Ngami, the central point of an inland water system of South Africa, once. forming a lake 20 m. long and io wide, but now little more than an expanse of reeds growing in a soft treacherous soil, below which brackish water is found. It is cut by 201° S. and 2 3 ° E. Ngami is the lowest point of a large depression in the plateau which comprises nine-tenths of Africa south of the Zambezi. The area which drains to it is bounded S. by the basin of the Orange, E. by the Matabele hills, N. by the western affluents of the Zambezi. The greater part of the Ngami water-system lies, however, N.W. of the lake (which for convenience it may still be called) in the tableland of Angola and German South West Africa. On the high plateau of Bihe, in the hinterland of Benguella, rise two large rivers, the Okavango and the Kwito, which uniting discharged their waters into Ngami. From the N.E. end of Ngami issued the Botletle or Zuga, a stream which runs S.E. and drains towards the Makarikari marsh, from which there is no outlet.

Although Ngami has dried up since 1890 the Okavango and its tributary the Kwito remain large rivers. The Okavango is known in its upper course as the Kubango. Its most remote source lies in about 122° S. and 162° E. and its length is over goo m. It flows first S. then S.E. and E. In about 18° S. and 202° E. it is joined on the north bank by the Kwito, a large navigable stream rising almost as far north as the Okavango. Its general course is S.E., but between 15° and 17° S. it flows S. and even S.W. Below the Kwito confluence the Okavango, which is also joined by various streams from the S.W. (German territory), is a rapid stream with an average breadth of over loo yds., and generally navigable as far as the Popa falls, in 21° 50' E. In the dry season, the water-level is from 4 to 20 ft. below the banks, but these are overflowed during the rains. At this period, April - June, some of the surplus water finds its way (in about Ig° S.) by the Magwekwana to the Kwando or Linyanti (Zambezi system), to which, it is conjectured, the whole body of water may have once flowed. Below the Magwekwana outlet the Okavango, now called the Taukhe or Tioghe, turns almost due S., enters a swampy reed-covered plain and is broken into several branches. In this region the effects of desiccation are marked. Through the swamps the river formerly entered Ngami.

The last 20 m. of the old channel are now dry and devoted to grain crops. Above this point the waters of the Okavango are diverted eastward through a channel called Tamalakane to the Botletle, the river which, as stated above, formerly flowed out of Ngami. The point of confluence is in about 20° S. 231° E., the Botletle above this point being merely a succession of pools. Below the junction the river bed is 150 to 200 yds. wide. The banks are 25 to 30 ft. high, and form steep white walls of sand compacted with lime, behind which the dark green forest rises. The stream is fringed with reeds harbouring countless waterfowl. The Botletle, whose bed is about loo m. in length, loses itself in a system of salt-pans - round or oval basins of varying size sunk to a depth of 30 to 45 ft. in the sandstone, and often bounded by steep banks. The outer pans are dry for a large part of the year, the whole system being filled only at the height of the flood-season in August. The Botletle, which receives in addition the scanty waters of the northern Kalahari, at this season reaches the Makarikari marsh. This marsh, occupying the N.E. corner of Bechuanaland, has also feeders from the Matabele hills in the direction of Bulawayo. During the rains the marsh is converted into a large lake. Much of the water is lost by evaporation; much of it sinks into some subterranean reservoir.

The evidence of travellers is conclusive that the country around Ngami is drying up. The desiccation appears to be rapid. In 1849 when David Livingstone visited Ngami the lake though shallow was of considerable extent. Later travellers reported progressive decrease in the size of the lake and in 1896 Sir F. D. Lugard and Dr Siegfried Passarge found it dry. Dr Passarge was told by the natives that the cessation of the river's flow was caused, about 1890, by a blocking of the channel by thousands of rafts.

Although the river system below the Magwekwana outlet of the Okavango is drying up, above that point there are long stretches of navigable water both on the Okavango and the Kwito, in all considerably over moo m. The Popa falls are the last of a series of six in a distance of 40 m., but none present serious engineering difficulties. The Magwekwana connexion with the Zambezi is a little over 100 m. long, and for more than half its course flows through a deep well-defined bed with a minimum width of 100 yards. The fall to the Linyanti affluent of the Zambezi is only a few feet and the country presents no obstacles to the construction of artificial channels.

Ngami is within the (British) Bechuanaland protectorate, about 5 0 in. E. of the frontier of German South-West Africa. The district is the home of the Batawana tribe of Bechuana, with whom is stationed a European magistrate. The tribes living along the lower Okavango are tributary to the Bechuana, and the blocking of the channel referred to was occasioned by their bringing to Ngami their annual tribute of corn.

See Bechuanaland and Kalahari. An account of the Ngami district is given in Die Kalahari by Dr Siegfried Passarge (Berlin, 1904). Of early books of travel consult C. J. Andersson's Lake Ngami (London, 1856) and The Okavango River (London, 1861).