Africa Lake Chad
river feet basin plateau
AFRICA LAKE CHAD Lake Chad, on the margin of the pastoral belt, is supplied by a large river named the Shari, coming from the moist forest country which lies nearer the equator; and the lake, which till recently was believed to have no outlet, overflows to north-eastward, fertilising a great wady, in which the waters become lost by evaporation as they are led towards the more arid country of the Sahara.
The southern area of continental drainage is of much smaller extent, and occupies the space of the desert zone which lies between the middle of the Zambeze basin and Damara Land. It centres in Lake Ngami, to which the Tioge river flows from the pastoral belt on the northwest. Several water-courses from the high Damara Land also take a direction toward this lake. The river Zuga carries off the overflow of Lake Ngami towards a series of salt lagoons which lie eastward near the edge of the plateau; but it becomes narrower and less in volume as it approaches these, and in some seasons scarcely reaches their bed.
Smaller spaces of continental drainage exist at various points near the eastern side of the continent. One of these occupies the depressed area between the base of the Abyssinian highland and the Red Sea, and is properly a continuation of the Sahara desert belt beyond the intervening plateau. In this space the Ilawash river, descending from the plateau, terminates before reaching the sea. Another interior basin lies in the plateau between the edge on which mountains Kenia and Kilima-njaro rise and the country east of the Victoria Lake, and includes several salt lakes. It is probable that the great Tanganyika Lake is the centre of a third basin of no outflow on this side of the great plateau; and Lake Shirwa, south-east of the Nyassa, constitutes a fourth.
The great lakes, which form such a prominent feature in African hydrography, are found chiefly in the southern and eastern regions of the continent, but they are distributed over all the systems of drainage. The Victoria and Albert Lakes of the Nile basin are great seas of fresh water ; and if their extent should ultimately prove to be nearly that which is at present believed, they rival the great American lakes for the place of the greatest expanse of fresh water on the globe. The former, the Victoria Lake, is at an elevation of about 3300 feet above the sea ; and its outline, as at present sketched on our maps, occupies an area of not less than 30,000 square miles. The Albert Lake, 2500 feet above the sea, is believed to have an extent not far short of this. Lake Bariugo, north-east of the Victoria, is reported to be a great fresh lake, discharging towards the Nile by a river which is possibly the Sobat tributary. Lake Tzana or Dembea, 60 miles in length, at a level of 6000 feet above the sea, on the Abyssinian plateau, is the only remaining great lake of the Nile basin.
The great expansions of the Chambeze-Lualaba river, presumably belonging to the river Congo, are the only other considerable lakes of the Atlantic drainage. The highest of them, Lake Bangweolo or Bemba, is described as being 150 miles in length from east to west, and at an elevation of 4000 feet ; Lake Moero, the next, extends through 60 miles ; Lakes Kamalondo or Ulenge, and the yet unvisited lakes of the same drainage, are described as of vast extent, and lie at an elevation of about 2000 feet above the sea.
Belonging to the drainage system of the Indian Ocean are, Lake Nyassa, 1500 feet above the sea, and stretching meridionally over an area of nearly 9000 square miles in the basin of the Zambeze ; and Lake Samburu, a reported lake of great extent, lying in the plateau edge north of !■Iount Kenia, and probably belonging to the basin of the Juba river. The great Lake Tanganyika, upwards of 10,000 square miles in area, and united by a broad channel with Lake Liemba in the south, occupies a deep longitudinal basin, girt with mountains ; it is 2800 feet above the sea level. As yet no outlet has been discovered for this vast lake, and the question whether it has or has not an overflowing river, is still undecided ; but its waters are not perfectly fresh, the drainage to it is small, and the probability is that the Tanganyika is a continental lake. Lake Shirwa, enclosed by mountains on the plateau edge southeast of Lake Nyassa, and 2000 feet above the sea, has brackish water, and no outlet.
Lake Chad, the greatest lake of the continental system of North Africa, is a shallow lagoon of very variable extent, with numerous islands : it lies at about 1100 feet above the sea; its waters are fresh and clear, and its overflow is carried off to north-eastward by the wady named Bahr-el-Ghazal.