African Unification Front
|
 |
|
|
|
|
 |
 |
|
THE GREAT RIFT VALLEY
Magadi, one of thousands of mineral lakes in the Rift Valley
The Great Rift Valley (also Great Earth Fissure), located in Eastern Africa, covers just over 2% of the continent and spreads over seven states. It is a massive Y-shaped crack in the Earth's crust and located in East Africa. The volcano has in it active volcanoes (red triangles) and the Afar Triangle (shaded, center) which is also triple junction (or triple point), where three plates are pulling away from one another: the Arabian Plate, and the two parts of the African Plate (the Nubian and the Somalian) splitting along the East African Rift Zone.
The eastward branch extends from the Gulf of Aden in the North to Mozambique in the South. The Western arm extends from Malawi in the South to Uganda in the North. The Western Arm is also known as the Albertine Rift The GRV contain a group of independent interior basins, extending from nearly being located in Ethiopia. The GRV contains the deepest lakes in the world, Lake Tanganyika being the deepest of all. It also contains hundreds of hotsprings, mineral lakes, and boiling mudpits. One of the most spectacular lakes is also the smelliest lake in the world. Lake Nyamunnuka in western Uganda changes colour, and sometimes has such a pungent smell that carries hundreds of miles downwind.
 The ecosystem of the GVR is astounding and many of East Africa's great wildlife lives in it. However, each state manages its own portion of the valley and there is no coordination that addresses the GRV as a unique and separate region. The African Union must consolidate funding of the entire valley under an integrated plan.
The Danakil basin is a very dry basin and only rainfall of more than 10 mm results in rapid floods lasting not more than a few hours. Annual runoff is less than 1 km3.
Lake Abbé, a salt lake on the border between Djibouti and Ethiopia, is in the Awash basin. The main part of the Awash basin is in Ethiopia, with annual rainfall ranging from 200 mm in the north to over 1900 mm in the south. The annual runoff in this basin is estimated at 4.6 km3.
The Central Lakes Basin, which groups several lakes, is also mainly located in Ethiopia, with a small part continuing into Kenya. Total annual runoff is estimated at 5.64 km3.
The Omo-Gibe basin, with rivers flowing into Lake Turkana is mainly located in Ethiopia and Kenya, with small parts in Sudan and Uganda. From Ethiopia the Omo and Gibe Rivers flow into the lake, while from Kenya the Turkwel and Kerio Rivers flow into the lake. Annual runoff in this basin is estimated at 16.1 km3.
In the southern part of Kenya and the northern part of Tanzania the Southern Lakes Basins are grouped, of which Lake Natron and Lake Eyasi are the most important ones.
IRRIGATION POTENTIAL
Agriculture in Djibouti is only possible with irrigation. The cultivable land is estimated at 6000 ha, but only 674 ha are equipped for irrigation, of which 300 ha are in the Rift Valley. No detailed information is available on irrigation potential, but with the available water resources it has been estimated at 1000 ha, of which 450 ha are estimated to be in the Rift Valley.
A narrow strip along the south-eastern border of Eritrea drains into the Danakil depression. Due to its closed topography and arid climate, it is characterized by highly saline soils and groundwater and has no agricultural potential.
Most of the irrigation developed to date in Ethiopia is located in the Awash basin. The irrigation potential in the Rift Valley region in Ethiopia is estimated at 790,000 ha. While the total water requirement is only one-fourth of the annual runoff, the development of the irrigation potential would require important storage works.
Less than 1% of Sudan lies in the Rift Valley. It is a swampy area. In Uganda lies the western arm of the Great Rift Valley. The water resources there are numerous and the irrigation potential is estimated high. The Mobuku Irrigation Scheme in Kasese is on of a few projects that makes the region one of the central sources of grain, cotton, and onions.
The climate in the Rift Valley in Kenya is quite remarkable. The rainfall is considerable, more than 1500 mm/year at the edges of the Rift Valley and decreasing rapidly to under 200 mm in the valley bottom. Irrigation water requirements are estimated at 10500 m3/ha per year in the north and at 12000 m /ha per year in the south. The irrigation potential, identified in the national water master plan and based on 80% dependable flow, is estimated at about 35900 ha in the northern Omo-Gibe basin and 16,600 ha in the southern Lower Ewaso Ng'iro Basin.
For the Kerio Valley, located in the Omo-Gibe basin, a special development authority was been established by the Kenyan Parliament to study the possibility of transferring water from the Lake Victoria basin to this basin.
For Tanzania an irrigation potential of only 1060 ha has been identified in the Rift Valley area. The Manonga River Basin located on the Vembere Plateau is an area for which plans to transfer water from the Lake Victoria basin have existed since the beginning of the 20th century. No water problems are expected for the development of this potential, though a lot of storage works will be necessary.
END
|
|
|
|
|
|
|
|
printable version
