Lake a Nyanza Albert

ALBERT, LAKE (A. NYANZA), Uganda, situated in I° 9' to 2° 17' S., and 30° 30' to 31° 35' E. Its greatest length is loom., its greatest breadth 22m., and its greatest depth 55ft. The area is approximately I,64osq.m. ; i.e., about the size of Lan cashire. The height of the lake surface above sea-level is given as 2,03 7f t., but this is liable to seasonal and other fluctuations.

The lake lies on the floor of the western branch of the Rift valley. Thermal springs occur at Kibiro, and again between the Murchison falls, on the Victoria Nile, and Wadelai. At Kibiro salt springs are exposed on the strand in the dry season, and give rise to a native trade in salt. At the southern end of Albert Nyanza is a wide plain, traversed by the Semliki river, which enters the lake through a swamp of tall weeds, chiefly ambach and papyrus. On both the eastern and western sides the walls of the Rift valley are close to the lake, the water in many cases washing the base of the cliffs. Elsewhere the narrow foreshore is thickly wooded. The ascent to the plateaux is generally by a series of abrupt steps. On the western side the mountains pre sent many pointed and conical summits, some of which may be nearly 8,000 feet above the lake ; on the eastern side the cliffs rise sharply for i,000 to 2,000 feet. On either coast wild ravines, densely wooded, break the outline of the mountains. Through these gorges and over the plateau-edge fall magnificent cascades. Towards the north the hills recede from the coast and on both sides flats extend for distances varying from 5m. to 15m. On the eastern side, 92m. from the southern end of the Nyanza, the Victoria Nile enters the lake, here not more than 6m. across, through a wilderness of woods, the delta of the Nile extending over 4m. The mouth of the main stream is obstructed by a bar of its own formation ; the current is sluggish ; there are many side channels, and the appearance of the lake gives no hint that a great river has joined its waters. For 5m. or 6m. north of the junction of the Victoria Nile the lake suffers no material diminu tion in width. Then, however, the eastern and western shores approach each other, and a current is perceptible flowing north. The lake has become the Bahr-el-Jebel, or Mountain river, as this section of the Nile is called. Albert Nyanza is shallow ; at its southern end the water for a considerable distance is not more than 3 f t. deep. The deepest soundings give only soft. to 55ft., the average depth being 3o to 4o feet.

The Albertine Basin of the Nile.

AlbertNyanza receives the whole of the drainage of Edward Nyanza and the Semliki river, and with them forms the "Albertine" Nile system. Its waters, as stated above, mingle with those of the Victoria Nile. There is evidence of very considerable shrinkage in the size of these lakes. Within human times the level of Albert Nyanza ap pears to have been I,000f t. higher than it is at present. The causes of this fall have not been fully explained: Both tectonic and climatic agencies may be involved. River erosion is probably also a complicating factor. In recent geological times the valley to the north of Edward Nyanza, then much larger than now, was blocked. The removal of the block led to the shrinkage of the lake and the formation of the Semliki, which found its way to the more northern lake—Albert Nyanza. Gradually the Semliki eroded its bed, and consequently the level of Edward Nyanza continued to fall. The process continues but is checked by the existence of the rock barrier which stretches across the Semliki. This stream leaves Edward Nyanza at its north-west end in o° 8' 3o S., and after a course of about 16om. enters Albert Nyanza in I° 9' N. In its upper and in its lower course the river flows either through high alluvial plains, in which it has scored a deep channel, or across swamp land. In the middle section, which has a length of some 75m., the river runs in a deep narrow valley covered with the densest forest. On the west this valley is bounded by the Congo mountains, which form the wall of the Rift valley, on the east by the mighty range of Ruwenzori, whose heights tower over I 6,000f t. above sea-level. In this length of 75m. the river falls in cataracts and rapids over Soo feet.

Albert Nyanza, on the other hand, is threatened in the distant future with destruction from another cause—the filling of its bed by the alluvium poured into it by the Semliki, the Victoria Nile and other streams. The Semliki receives directly or indirect ly the whole of the drainage of Ruwenzori, and also that of the eastern face of the Congo mountains as well as the drainage basin of Edward Nyanza. The Semliki, as it emerges from the region of forest and cataracts, and deposits much of its burden, becomes sluggish as its slope flattens out. This process has formed a large plain at the south end of Albert Nyanza, which has seriously encroached upon the lake. At the northern end of the lake the sediment brought down by the Victoria Nile is producing a similar effect. Nyamsasi, which was an island at the south west end in 1889, has become a peninsula. Islands which in 1876 were on the east coast no longer exist ; they now form part of the foreshore. On the other hand, the shrinkage of the lake level caused the appearance in 1885 of an island where in 1879 there had been an expanse of shallow water. It seems probable that, in a period geologically not very remote, the "Albertine" sys tem will consist of one great river, extending from the northern slopes of the Kivu range, where the Ruchuru has its rise, to the existing junction of the Victoria Nile with Albert Nyanza.

The combined drainage area, including the water surface of Edward Nyanza, the Semliki and Albert Nyanza, is some 16,600 sq.m. Throughout this area the rainfall is heavy (4oin. to 6oin. or more per annum), the volume of the Semliki in flood being not less than 7oocu.m. per second. Of the water received by Albert Nyanza annually (omitting the Victoria Nile from the calculation) between 5o% and 6o% is lost by evaporation, whilst 24,265,00o,oQocu.m. are annually withdrawn by the Bahr-el-Jebel. The "Albertine" system plays a comparatively insignificant part in the annual flood rise of the White Nile, but to its waters are due the maintenance of a constant supply to this river through out the year.

Discovery and Exploration.

Albert Nyanza was first reached by Samuel Baker on March 14, 1864, near Vacovia, a small village of fishermen and salt-makers on the east coast. Albert Nyanza was entered on his map as a vast lake extending . about 38om. But the circumnavigation of the lake by Gessi Pasha (1876), and by Emin Pasha in 1884, showed that Baker had been deceived as to the size of the lake. The lake forms part of the (British) Uganda Protectorate, but the north-west shores were leased in 1894 to the Congo Free State. Of this leased area a strip 15m. wide, giving the Congo State a passageway to the lake, was to remain in its possession after the determination of the lease. (See also NILE.) BIBLIOGRAPHY.-W. Garstin, Report upon the Basin of the Upper Bibliography.-W. Garstin, Report upon the Basin of the Upper Nile (Egypt, No. 2, 1904) ; H. G. Lyons, The Physiography of the River Nile and its Basin (Cairo, 1906) ; J. W. Gregory, The Rift Valley and Geology of East Africa (1921) ; E. Krenkel, Geologie Afrikas (1925).