Victoria Nyanza, the largest lake in Africa and chief reservoir of the Nile, lying between 0° 20' N. to 3° S. and 31° 40' to 34° 52' E. Among the fresh-water lakes of the world it is exceeded in size by Lake Superior only and has an area of over 26,000 sq. m., being nearly the size of Scotland. In shape it is an irregular quadrilateral, but its shores, save on the west, are deeply indented. Its greatest length, taking into account the principal gulfs, N. to S. is 250 m., its greatest breadth 200 m. Its coast-line exceeds 2000 m. It fills a depression in the central part of the great plateau which stretches between the western (Albertine) and eastern rift-valleys (see Africa, § I), and has an elevation of about 3720 ft. above the sea. (For the altitude see Geog. Jour., March 1907 and July 1908.) Its greatest ascertained depth is some 270 ft., which compares with soundings of 2000 ft. on Tanganyika and 2500 ft. on Nyasa. Victoria Nyanza is remarkable for the severe and sudden storms which sweep across it, rendering navigation dangerous. It contains many groups of islands, the majority being near the coast-line. The lake is full of reefs, many just below the surface of the water, which is clear and very fresh. It is abundantly stocked with fish. Geological research shows that the land surrounding the lake consists of gneiss, quartz and schistose rocks, covered, in the higher regions, with marl and red clay, and in the valleys with a rich black loam.
Shores and Islands
The shores of the lake present varied aspects. The western coast, which contains no large indentations, is, in its southern part, backed by precipices of 300 or more ft. high, behind which rise downs to thrice the height of the cliffs. Going north, the hills give way to papyrus and ambach swamps, which mark the delta of the Kagera. Beyond the mouth of that river the hills reappear, and increase in height, till on reaching the N.W. corner of the nyanza they rise some 500 ft. above the water. This western shore is marked by a continuous fault line which runs parallel to the lake at a short distance inland. The northern coast of the lake is very deeply indented and is marked throughout its length by rocky headlands jutting into the waters. This high land is very narrow, and the streams which rise on its northern face within a mile or two of the nyanza drain north away from the lake. On a promontory about 30 m. east of the Katonga (see below) is Entebbe, the port of Uganda and seat of the British administration. The chief indentations on the north side are Murchison Bay and Napoleon Gulf, the entrance to the last named being partly filled by the triangular shaped island of Buvuma or Uvuma (area 160 sq. m.). Napoleon Gulf itself is deeply indented, one bay, that of Jinja, running N.W. and being the outlet of the Nile, the water here forcing its way through the rock-bound shore of the lake. The north-east corner of the lake is flat and bare. A narrow channel, partly masked by islands, leads into Kavirondo Gulf, which, with an average width of 6 m., extends 45 m. E. of the normal coast-line -- a fact taken advantage of in building the railway from Mombasa to the lake. A promontory, 174 ft. above lake-level, jutting into the small bay of Ugowe, at the north-east end of Kavirondo Gulf, is the point where the railway terminates. The station is known as Port Florence. On the south side of the gulf tall hills approach, and in some cases reach, the water's edge, and behind them towers the rugged range of Kasagunga with its saw-like edge. Proceeding south the shore trends generally south-west and is marked with many deep inlets, the coast presenting a succession of bold bluffs, while inland the whole district is distinctly mountainous. At the S.E. corner of the lake Speke Gulf projects eastward, and at the S.W. corner Emin Pasha Gulf pushes southward. Here the coast is barren and hilly, while long ridges of rock run into the lake.
The largest island in the lake, Ukerewe, on the S.E. coast, immediately north of Speke Gulf, is almost a peninsula, but the strip of land connecting it with the shore is pierced by two narrow channels about 3/4 of a mile long. Ukerewe is 25 m. long, and 12 broad at its greatest width. It is uninhabited, wooded and hilly, rising 650 ft. above the lake. At the N.W. corner of the nyanza is the Sesse archipelago, consisting of sixty-two islands. The largest island in this group, namely, Bugala, is narrow, resembling the letter S in shape, and is almost cut in two in the middle. Most of these islands are densely forested, and some of them attain considerable elevation. Their scenery is of striking beauty. Forty-two were inhabited. (To prevent the spread of sleeping sickness the inhabitants were removed to the mainland in 1909). Buvuma Island, at the entrance of Napoleon Gulf, has already been mentioned. Between it and as far as the mouth of Kavirondo Gulf are numerous other islands, of which the chief are Bugaia, Lolui, Rusunga and Mfwanganu. In general characteristics and the beauty of their scenery these islands resemble those of the Sesse archipelago. The islands are of ironstone formation overlying quartzite and crystalline schists.
Rivers
The Kagera, the largest and most important of the lake affluents, which has its rise in the hill country east of Lake Kivu, and enters the west side of the nyanza just north of 1° S., is described in the article Nile, of which it is the most remote head-stream. The other rivers entering Victoria Nyanza from the west are the Katonga and Ruizi, both north of the Kagera. The Katonga rises in the plateau east of the Dweru branch of Albert Edward Nyanza, and after a sluggish course of 155 m. enters Victoria Nyanza in a wide swamp at its N.W. corner. The Ruizi (180 m.) is a deep, wide and swift stream with sinuous course flowing in part through great gorges and in part through large swamps. It rises in the Ankole district and reaches the nyanza a little north of the Kagera. Between the Katonga and the Nile outlet, the rivers which rise close to the lake drain away northward, the watershed being the lake shore. On the N.E. side of the nyanza, however, several considerable streams reach the lake -- notably the Sio, Nzoia and Lukos (or Yala). The Nzoia (150 m.), the largest of the three, rises in the foothills of the Elgeyo escarpment and flows swiftly over a rocky bed in a south-westerly direction, emptying into the lake south of Berkeley Bay. On the east side the Mara Dabagh enters the lake between 1° and 2° S. It is, next to the Kagera, the largest of the lake tributaries. All the rivers mentioned are perennial, and most of them bring down a considerable volume of water, even in the dry season. On the S., S.E. and S.W. shores a number of short rivers drain into the lake. They traverse a treeless and arid region, have but an intermittent flow, and are of little importance in the hydrography of the district. The only outlet of the lake is the Nile (q.v.).
Drainage Area, Rainfall and Lake Level
The very important part played by the Victoria Nyanza in the Nile system has led to careful study of its drainage basin and rainfall and the perplexing variations in the level of the lake. The area drained by the lake covers, with the lake itself, 92,240 sq. m. In part it is densely forested, part consists of lofty mountains, and a considerable portion is somewhat arid tableland. According to the calculations of Sir William Garstin the rainfall over the whole area averages 50 in. a year. Allowing that as much as 25% of this amount enters the lake, this is equivalent to a total of 138,750,000,000 cub. metres in a year. Measurements at the Ripon Falls show that 18,000,000,000, or some 13% of this amount, is taken off by the Nile, and when allowance has been made for the annual rise and fall of the lake-level it is apparent that by far the greater part of the water which enters the nyanza is lost by evaporation; in fact, that the amount drawn off by the river plays a comparatively small part in the annual oscillation of the water surface. Rain falls more or less in every month, but is heaviest during March, April, May and again in September, October and November. The level of the lake is chiefly affected by the autumn rains and generally reaches its maximum in July. The annual rise and fall is on an average from 1 to 3 ft., but between November 1900 and June 1901 a difference of 42 in. was recorded. Considerable speculation was caused by the fact that whereas in 1878-79 the lake-level was high, from 1880 to 1890 the level was falling, and that after a few years (1892-95) of higher level there was, from 1896 to 1902, again a steady fall, amounting in seven years to 30 in. in the average levels of the lake. In 1903, however, the level rose and everywhere the land gained from the lake in the previous years was flooded. These variations are attributed by Sir William Garstin to deficiency or excess of rainfall. Any secular shrinking of the lake in common with the lakes of Central Africa generally must be so gradual as to have no practical importance. It must also be remembered that in such a vast sheet of water as is the nyanza the wind exercises an influence on the level, tending to pile up the water at different parts of the lake. The winds may also be the cause of the daily variation of level, which on Speke Gulf has been found to reach 20 in.; but this may also partake of the character of a "seiche." Currents setting towards the north or north-west have been observed in various parts of the lake.
Discovery and Exploration
The quest for the Nile sources led to the discovery of the lake by J. H. Speke in 1858, and it was by him named Victoria in honour of the queen of England. In 1862 Speke and his companion, J. A. Grant, partially explored the N.W. shore, leaving the lake at the Nile outlet. Great differences of opinion existed as to its size until its circumnavigation in 1874 by H. M. Stanley, which proved it to be of vast extent. The invitation sent by King Mtesa of Uganda through Stanley to the Christian missionaries led to the dispatch from England in 1876 of the Rev. C. T. Wilson, to whom we owe our first detailed knowledge of the nyanza. Mr Wilson and Lieut. Shergold Smith, R.N., made, in 1877, the first voyage across the nyanza. Lieut. Smith and a Mr O'Neill, both members of the Church Missionary Society, were in the same year murdered on Ukerewe Island. In 1889 Stanley further explored the lake, discovering Emin Pasha Gulf, the entrance to which is masked by several islands. In 1890 the ownership of the lake was divided by Great Britain and Germany, the first degree of south latitude being taken as the boundary line. The southern portion, which fell to Germany, was visited and described by scientists of that nation, whose objects, however, were not primarily geographic. At the instance of the British Foreign Office a survey of the northern shores of the lake was carried out in 1899-1900 by Commander B. Whitehouse, R.N. The same officer, in 1903, undertook, in agreement with the German government, a survey of the southern shores. Commander Whitehouse's work led to considerable modification of the previously accepted maps. He discovered numerous islands and bays whose existence had previously been unknown.
Previously to 1896 navigation was confined to Arab dhows, which trade between the south end of the lake and Uganda, and to canoes. In the year named a small steamer (the "Ruwenzori") was launched on the lake by a Zanzibar firm, while in 1900 a somewhat larger steamer (the "William Mackinnon"), built in Glasgow at the instance of Sir W. Mackinnon, and afterwards taken over by the British government, made her first trip on the lake. In 1903, the year in which the railway from Mombasa to the lake was completed, a steamer of 600 tons burden was launched at Port Florence. Since that date trade has considerably increased.
See NILE and UGANDA and the British Blue-book Egypt No. 2 (1904), which is a Report by Sir Wm. Garstin upon the Basin of the Upper Nile. This report, besides giving (pp. 4-24) much original information upon the Victoria Nyanza, summarizes the information of previous travellers, whose works are quoted. In 1908 the British Admiralty published a chart of the lake (scale 4 in. to the mile) from the surveys of Commander Whitehouse. Non-official books which deal with the lake include: C. T. Wilson, Uganda and the Soudan (London, 1882); (Sir) F. D. Lugard, The Rise of our East African Empire, vol. ii. (London, 1893); Franz Stuhlmann, Mit Emin Pasha, &c. (Berlin, 1894); Paul Kollmann, The Victoria Nyanza (English translation; London, 1899); E. G. Ravenstein, "The Lake-level of the Victoria Nyanza," Geographical Journal, October 1901; Sir H. H. Johnston, The Uganda Protectorate (London, 1902). In most of these publications the descriptions of the lake occupy but a small part. (W. E. G.; F. R. C.)
