UBANGI, a river of Equatorial Africa, the chief northern affluent of the Congo (q.v.). The Ubangi (otherwise Mubangi or Mobangi) enters the Congo by various mouths between o 22' and o 37' S. and 17 40' and 17 50' E. The main channel, fully i m. wide, joins the Congo in o 31' S. The Ubangi is formed by the junction of the Mbomu and the Welle, both of which rise on the north-eastern rim of the Congo basin.
The water-parting between the Bahr-el-Ghazal affluents (Nile system) and the Mbomu headstreams is not very clearly marked, but high hills running parallel with the Nile between Albert Nyanza and Dufile sharply separate the valley of the Welle and other westflowing streams from that of the Mountain Nile. The chief of the headstreams of the Welle (known in its upper course as the Kibali) rises on the western slope of a hill about 40 m. west of Wadelai. It is joined by several small streams, the main river flowing in a W.N.W. direction. After a course of over 700 m. (during which it receives one large southern tributary the Bomokandi and other considerable affluents) the Welle joins the Mbomu in 4 10' N. 22 37' E. The Mbomu, which has two large northern tributaries, the Shinko and the Balo, rises in 4 50' N. 27 12' E. For some distance it runs parallel to and about 100 m. north of the lower course of the Welle. About 23 12 E. it turns sharply south until its junction with the Welle. In its lower course the Mbomu is interrupted by many falls and rapids. A short distance below the junction of the Mbomu and Welle the Kotto, coming from beyond 8 N., on the borders of Darfur, and forming the most northerly extension of the Congo basin, enters the united stream, now known as the Ubangi, on the right bank. The remaining tributaries, mostly on the right bank, are smaller, but the Kemo, which joins the Ubangi near its most northern point (5 8 N.), is of some importance as offering water communication to within a short distance of the Shari basin. Below the Kemo confluence the Ubangi, which has hitherto continued to flow W.N.W., makes a great bend south and runs into the Congo after a southerly course of 400 m. Shortly after receiving the Kemo the river forces its way through a line of hills whose tops rise 600 to 800 ft. above the banks of the stream. Here are the Zongo or Grenfell rapids, which are a barrier to navigation save for small boats at flood season. Above the Zongo rapids the river is navigable up to the confluence of the Welle and Mbomu, and the Welle is navigable at high flood up to the Bomokandi confluence in 26 8', though the stream is much interrupted by rapids.
From the Mbomu-Welle confluence to the junction of the Ubangi with the Congo the river has a course of fully 700 m., while the Ubangi-Welle combined exceeds 1400 m. From its mouth to Zongo rapids, a distance of 350 m., the stream is navigable by steamers drawing 3 ft. of water. In general the Ubangi flows through a fertile and forested region.
The Welle was discovered from the north by G. A. Schweinfurth in 1870; i.e. seven years before the discovery of the course of the Congo by H. M. Stanley. By Schweinfurth the Welle was believed to belong to the Chad system, but W. Junker, who (1882- 1883) followed the river to near its confluence with the Mbomu, made it clear that the Welle belonged to the Congo system. In 1885 the Rev. George Grenfell, of the Baptist Missionary Society (who had discovered the mouth of the river in 1884), ascended the Ubangi as far as the Zongo rapids. He was followed in 1886- 1889 by the Belgian A. van Gele, who in the last-named year finally established the identity of the Ubangi with Schweinfurth's Welle. The Mbomu was discovered from the north in 1877 by a Greek, Dr P. Potagos, and its upper course was followed for some distance by Junker. The Ubangi and the Mbomu form the frontier between Belgian Congo and French Congo, the northern banks of both streams belonging to France.
See, besides the works of Schweinfurth, Junker and other travellers, A. J. Wauters, Les Bassins de I' Ubangi (inferieur) et de la Sanga, with map (Brussels, 1902); Dr Cureau's map (i : 1,000,000) of the upper Ubangi in La Geographic (October 1900) ; the CONGO and works there cited.
Note - this article incorporates content from Encyclopaedia Britannica, Eleventh Edition, (1910-1911)