VOLTA, the largest river of the coast of Upper Guinea, between the Gambia and the Niger, with a length of about 900 m. Its mouth and the greater part of its course are in British territory. Its lower course had been known since the discoveries of the Portuguese, from whom it received (15th century) its name on account of the winding nature of its stream. It was not, however, until the last fifteen years of the 19th century that the extent of its basin — extending far north within the bend of the Niger — was made known.
There are two main upper branches, the Black and the White Volta. Their sources lie on the grassy plateaus north of the forest belt of the Guinea coast, the Black Volta rising (as the Baule) in about 11° N. 4° 50' W. Its course is at first E. and N.E., to 12° 25' N., at which point, after receiving a tributary from nearly 14° N. — the most northerly point of the basin, — it turns sharply south. From the eleventh to the ninth parallel the river forms the boundary between the Northern Territories of the Gold Coast (British) and the French Ivory Coast colony. The southerly course of the stream ceases at 8° 15' N. where it is deflected E., and even N., by a mountain range composed of sandstone and granite, which it finally breaks through by a narrow pass, in which its width is only some 60 yds. Elsewhere it has a general width of 150 to 200 yds. In 0° 50' W. it receives the White Volta, which flows generally south from about 13° N. and likewise breaks through a narrow gap in the plateau escarpment. Both rivers shrink greatly in the dry season, reaching their lowest level at the end of January. Below the junction the Volta flows S.E. and S., turning, however, E. for 40 m. just north of 6°. In 7° 37' N. it receives on the left bank a large tributary, the Oti, coming from 12° N. In its lower course, through the forest the river has often a width of over half a mile, with a depth in places of 40 to 50 ft. in the rains, but in 6° 18' N. it traverses a pass in which its width is narrowed to 30 yds. Its use as a waterway is limited by a number of rapids, the lowest of which occur in 6° 7' N., above the trading port of Akuse. Its mouth is obstructed during the greater part of the year by a bar. The river is usually navigable by small vessels from its mouth for about 60 m.
The lower Volta was explored by M. J. Bonnat in 1875, but the upper basin was first traversed by the German traveller G. A. Krause (1886-87) and the French captain L. G. Binger (1888). It has since been explored by a number of colonial officials — German, French and British. Between 6° 41' and 8° 8' N. the Volta forms the boundary between the Gold Coast and Togoland.