Probably not less than four-fifths of the territory of Venezuela belong to the drainage basin of the Orinoco (q.v.).
It is roughly mountainous, and belongs to the closed drainage basin of western Argentina, centring in the province of Mendoza.
In the extreme north-east corner of the republic where the Brazilian Guiana plateau slopes toward the Atlantic there is a small area lying outside the drainage basin of the Amazon.
All this region belongs to the drainage basin of the Orinoco, and rivers of large volume flow down between these spurs.
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, in a lesser degree, by other streams. The Semliki receives directly or indirectly 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 Albert Edward Nyanza.
North and parallel with its course is a low watershed, which separates its drainage basin both from that of the Sao Francisco and from that of the Parnahyba, the northern confluent of the Parana.
It lies partly within the drainage basin of the Orinoco and partly within that of the Rio Negro, an affluent of the Amazon.
The Pontotoc ridge separates the drainage system of the Mississippi from that of the Tombigbee; extending from the northeastern part of the state southward, this ridge divides in Choctaw county, the eastern branch separating the drainage basin in the Pascagoula from that of the Pearl, and the western branch separating the drainage basin of the Pearl from that of the Big Black and the Mississippi.
Of the Colorado river; the northern edge being formed by the divide of the drainage basin of the Columbia river, the eastern by that of the Colorado, the western by the central part of the Sierra Nevada crest, and by other high mountains.
The latter, the remnants of which are represented to-day by Great Salt, Sevier and Utah Lakes, had a drainage basin of some 54,000 sq.