principal tributary feeding Lake Chad in north-central Africa. It flows through Chad and the Central African Republic and is formed by the Bamingui (its true headstream), the Gribingui, and the Ouham (Ouham River) (q.v.), which brings to it the greatest volume of water. Near Sarh the Chari is joined on its right bank by the Baḥr Aouk, the Baḥr Kéita, and the Baḥr Salamat, parallel streams that mingle in an immense floodplain. Baḥr Salamat, which rises in Darfur in The Sudan, in its middle course is fed by the waters of Lac (lake) Iro. The river then divides into numerous branches that spread into a delta and end in the Chari. Baḥr Aouk, which forms the boundary between Chad and the Central African Republic, also rises in Darfur and sluggishly drains an immense marshy plain. In the dry season it is sometimes reduced to a succession of stagnant ponds; its floodwaters empty into the Chari in an extensive delta. Downstream from Sarh the Chari crosses the Gay Rapids near Niellim, broadening out to 3 or 4 mi (5 or 6.5 km) in width, its lower reaches dividing into many channels. At N'Djamena to the west it joins the Logone and flows into Lake Chad through several distributaries. The total length of the Chari is about 870 mi (1,400 km). The Chari basin covers 250,000 sq mi (650,000 sq km), and the river unites the drainage of the southern part of the Chad inland basin. Steamboats navigate the main river for more than 530 mi in the wet season. The existence of the Chari was made known to Europeans by the British explorers Dixon Denham, Hugh Clapperton, and Walter Oudney, who reached Lake Chad in 1823.