JUBA or JUB, a river of east Africa, exceeding i,000 m. in length, rising on the south-east border of the Abyssinian high lands and flowing south, leaving Abyssinia at Dolo and then flowing through Italian Somaliland. It is formed by the junction of three streams, all having their source in the mountain range north-east of Lake Rudolf which is the water-parting between the Nile basin and the rivers flowing to the Indian ocean.
Of the three headstreams, the Web, the Ganale and the Daua, the Ganale is the central river. It has two chief branches, the Black and the Great Ganale. The last-named, the most remote source of the river, rises in 7° 3o' N., 38° E. at an altitude of about 7,500 ft. The banks are clothed with dense jungle and the hills beyond with thorn-bush. Lower down the river has formed a narrow valley, 1,5oo to 2,000 ft. below the general level of the country, after which it enters a large slightly undulating grass plain which extends south of the valley of the Daua and occu pies all the country eastward to the junction of the two rivers. The Web, which near its source passes through a canon 5oo ft. deep and then underground for some distance, joins the Ganale (left) above its junction with the Daua (right). The latter is similar to the Ganale and their courses are parallel.
Below the Daua the river, now known as the Juba, receives no tributary of importance. It first flows in a valley bounded, espe cially towards the west, by the escarpments of a high plateau, and containing the towns of Lugh (in 3° 5o' N., the centre of active trade), Bardera, with Serenli opposite to it 387 m. above the mouth at a crossing-place for caravans. Beyond I° 45' N. the country becomes more level and the course of the river very tortuous. Just south of the equator channels from the long,
branching Lake Deshekwama, fed by the Lakdera river, enter from the west, and in o° 15' S. the Juba enters the sea across a dangerous bar, which has only one fathom of water at high tide. From its mouth to 20 m. above Bardera, where at 2° 35' N. rapids occur, the Juba is navigable by shallow-draught steamers. Just above its mouth it is a fine stream 25o yd. wide, with a current of 2 knots.
The hills in which the river rises are formed of Archean rocks (schists, gneisses, granites, etc.). In its middle course it crosses Triassic rocks and lower down passes over the Jurassic formations which disappear beneath the coastal alluvium near Sarori. Below the mountainous region of the headstreams the Juba and its tribu taries flow through a country generally arid away from the banks of the streams. The soil is sandy, covered either with thorn-scrub or rank grass, which in the rainy season affords herbage for the herds of cattle, sheep and camels owned by the Boran Gallas and the Somali who inhabit the district. But by the banks of the lower river the character of the country changes. The soils of the Gosha district of the Lower Juba are clayey, but remarkably rich in lime and magnesia and with adequate amounts of potash and phosphoric acid. Here are considerable tracts of forest, and the level of flood water is higher than much of the surrounding land. This low-lying fertile belt stretches for about 30o m., but is not more than a mile or two wide. In the river valley maize, rice, cotton and other crops are cultivated.