The Congo's biggest right-bank tributary may once have fed Lake Chad
The Ubangi runs about 1,060 km through Central Africa, marking borders between three countries on its way to the Congo. Geologists think its upper reaches once drained north toward Lake Chad, and for decades engineers have dreamed of sending some of its water back there.
The Ubangi is born where two rivers meet: the Mbomou, averaging roughly 1,350 cubic metres per second, and the Uele, averaging about 1,550. From that junction it heads west, serving as the frontier that separates the Central African Republic (CAR) from the Democratic Republic of the Congo (DRC), then swings southwest past Bangui, the CAR capital. Some 100 km below the city the border role changes hands, and the river instead divides the DRC from the Republic of the Congo until it reaches the Congo River at Liranga.
On its own the Ubangi stretches about 1,060 km, but counting the Uele, its longest feeder, the system reaches 2,270 km. It gathers water from a basin of roughly 651,915 square kilometres. At Bangui the flow swings enormously with the seasons, from around 800 to 11,000 cubic metres per second, averaging near 4,000; by the mouth the yearly mean is closer to 6,000. Together with the Congo it forms a vital boat route linking Bangui with Brazzaville.
Its present course may be an accident of capture. Researchers believe the upper Ubangi originally flowed into the Chari River and on to Lake Chad, until the Congo system stole it in the early Pleistocene. That ancient link gives an odd echo to modern engineering ambitions.
In the 1960s a scheme called Transaqua proposed diverting Ubangi water into the Chari to refill the shrinking Lake Chad, promising fisheries and better farming for tens of millions of people across central Africa and the Sahel. Nigerian engineer J. Umolu and the Italian company Bonifica put forward transfer plans in the 1980s and 1990s. The Lake Chad Basin Commission floated its own version in 1994, member heads of state endorsed diversion at a summit in March 2008, and a month later the commission invited bids for a feasibility study.
Source: Ubangi River
