Source: The Library Of Congress Country Studies
Physiographically, Somalia is a land of limited contrast. In the north,a scrub-covered, semiarid, and generally drab area, known as the guban (scrub land), is characterised by broad, shallow watercourses that are beds of dry sand except in the rainy seasons.
Southward of the Karkaar mountains the land descends to an elevated plateau devoid of perennial rivers. This region of broken mountain terrain, shallow plateau valleys, and usually dry watercourses is known to the Somalis as the Ogo.
The western part of the Ogo plateau region is crossed by numerous shallow valleys and dry watercourses. Most important, the western area has permanent wells to which the predominantly nomadic population returns during the dry seasons. The western plateau slopes gently southward and merges imperceptibly into an area known as the Haud,where there are natural depressions that during periods of rain become temporary lakes and ponds.
Southwestern Somalia is dominated by the country's only two permanent rivers, the Jubba and the Shabeelle. With their sources in the Ethiopian highlands, these rivers flow in a generally southerly direction, cutting wide valleys in the Somali Plateau as it descends toward the sea; the plateau's elevation falls off rapidly in this area.
The Jubba River enters the Indian Ocean at Chisimayu. Although the Shabeelle River at one time apparently also reached the sea near Merca, its course is thought to have changed in prehistoric times. The Shabeelle now turns southwestward near Balcad (about thirty kilometers north of Mogadishu) and parallels the coast for more than eighty-five kilometers. The river is perennial only to a point southwest of Mogadishu; thereafter it consists of swampy areas and dry reaches and is finally lost in the sand east of Jilib, not far from the Jubba River. During the flood seasons, the Shabeelle River may fill its bed to a point near Jilib and occasionally may even break through to the Jubba River farther south.