Boundaries

The xeric systems of this ecoregion include the Wabi Shebelle and Juba basins with the ecoregion extending from Kenya to Somalia along the coast of the Indian Ocean and inland to the Ethiopian Highlands [525]. During flooding, the rivers often spill over their banks and inundate adjacent floodplains.

Freshwater habitats

Draining from the southeastern escarpment of the eastern Ethiopian highlands, the Wabi Shebelle and the Fafan Rivers flow through the Somalian desert, although they do not reach the Indian Ocean. The Wabi Shebelle is the major river of the central Somali region. Rising between the Arsi and Bale Mountains, it flows in a southeasterly direction to Somalia. In its lower section, the Wabi Shebelle and its main seasonal tributary from the east, the Fafan, cut through a series of wide, flat shelves of sedimentary rocks made of sandstone, limestone, and gypsum. Wabi Shebelle, with a catchment area of 205,407 km², winds a length of 1340 km inside Ethiopia, and a further 660 km in Somalia (Ethiopian Mapping Authority 1988). The Wabi Gestro, the Ghenale River, and the Dawa Parma River drain the southwestern escarpment of the eastern Ethiopian highlands. These rivers unite and become the Juba River, which eventually drains into the Indian Ocean (Westphal 1975). These Juba tributaries arise just east of Abaya and Chamo Lakes, but are separated from the lake drainages by a high mountainous divide. According to Roberts (1975), midway between the lower courses of the Wabi Shebelle and the Juba there is a low-lying limestone plateau with extensive underground waterways radiating out from it.

Terrestrial habitats

Floodplains are often covered in a tangled growth of small bushes and herbs, which include wild relatives of cotton. Large trees are not naturally found on the floodplains, but heat-tolerant species, including Hyphaene thebaica, have been planted in settlements (Ethiopian Wildlife and Natural History Society 1996).

Description of endemic fishes

Endemic fish, including Bagrus urostigma, Labeo boulengeri, Labeo bottegi, and Synodontis geledensis, live in the rivers of this ecoregion. Most of the Nilotic species found in Lake Abaya, with the exception of Hyperopisus bebe, are also present in the Wabi Shebelle-Juba drainage (Roberts 1975). Another important feature of the area is the presence of subterranean waterways, which are inhabited by the endemic monotypic fish genera Uegitglanis and Phreatichthys. Both the clariid catfish (U. zammaranoi)and the cyprinid (P. andruzzii)lack visible eyes and are depigmented and scaleless.

Ecological phenomena

A continuous escarpment, running in a wide curve from the Kenyan border to northern Somalia, forms the western and northern borders of this ecoregion, while the southwestern part of this escarpment forms the eastern wall of the Rift Valley. The escarpment rises northwards and attains its maximum elevation of over 3,000m near the Chilalo Massif in Ethiopia. Several endemic fishes live in the streams and subterranean waters of this xeric ecoregion.

Justification for delineation

A continuous escarpment, running in a wide curve from the Kenyan border to northern Somalia, forms the western and northern borders of this ecoregion, while the southwestern part of this escarpment forms the eastern wall of the Rift Valley. The escarpment rises northwards and attains its maximum elevation of over 3,000m near the Chilalo Massif in Ethiopia. Several endemic fishes live in the streams and subterranean waters of this xeric ecoregion

Level of taxonomic exploration

Poor. The native freshwater flora and fauna of this vast ecoregion has been poorly investigated. Although the riparian vegetation has been described to some extent, little is known about the upland vegetation. Without better information, identification of conservation priorities is difficult.