General description of the Nile River Basin in Africa, Essays (high school) of Geography

Download General description of the Nile River Basin in Africa and more Essays (high school) Geography in PDF only on Docsity! 1 General description of the Nile River Basin 1. Introduction The River Nile is considered as the longest river on the planet. The length of the River Nile from its remote sources to its mouth on the Mediterranean Sea is around 6700 km. Its catchments cover roughly 10 % of the African landmass, with an area of 3.11 million km², it reaches out from 4o South to 31o North latitude and from around 21o 30/East to 40o 30/ longitude, and spreads over 11 nations (Uganda, Tanzania, Kenya, Congo, Rwanda, Burundi, Sudan, South Sudan, Ethiopia, Eretria Egypt). Table (1) shows a portion of the major rivers in the world. Table (1) Major rivers in the world River Length (km) Catchment Area million (km2) Water yield per year (BCM) Nile 6700 3.11 84 Amazon 6500 7.780 5300 Congo 4700 3.82 1300 Niger 4100 2.274 177 Mississippi 6000 3.22 550 Danube 2900 0.816 206 Rhine 1320 0.224 70  Km = Kilometre  BCM = Billion cubic meter The Nile Basin is charcterised by its size and variety of climates and topographies. Therefore, it constitutes one of the dominant complexes of all major river basins in the world. However, the river's annual water flow is relatively small combared with other rivers. Figure (1) shows the Nile Basin map. Table (2) shows the Nile Basin countries in terms of areas and average annual rainfall. Table (2) Nile Basin countries areas and average rainfall Country Total area of the country (km2) Area of the country within the nile basin (km²) Percentage of total area of basin (%) Percentage of total area of country (%) Average annual rainfall in the basin area (mm) Min. Max. Mean Burundi 27834 13260 0.4 47.6 895 1570 1110 D.R. Congo 2344860 22143 0.7 0.9 875 1915 1245 Egypt 1001450 326751 10.5 32.6 0 120 15 Eritrea 121890 24921 0.8 20.4 240 665 520 Ethiopia 1100010 365117 11.7 33.2 205 2010 1125 Kenya 580370 46229 1.5 8 505 1790 1260 Rwanda 26340 19876 0.6 75.5 840 1935 1105 Sudan&South Sudan 2505810 1978506 63.6 79 0 1610 500 Tanzania 945090 84200 2.7 8.9 625 1630 1015 Uganda 235880 231366 7.4 98.1 395 2060 1140 For Nile Basin 3112369 100 2 Figure (1) Map of Nile River Basin 5 Bahr el Jebel, the average annual discharge at Mongalla, which is considered the southern end of the Sudd region, is about 30 BCM per year in average. Unfortunately, half of this water is lost by seepage, direct evaporation and evapotranspiration in the Sudd region and thus the average flow reaching Malakal station from Bahr el Jebel and Bahr el Zeraf is only 15 BCM per year. 3. Flow Contribution of the Ethiopian highlands to the Nile 3.1 The Sobat River The Sobat River, which is mainly constitutes from the two rivers of Baro and Pibor coming from the Ethiopian highlands, joins the White Nile in South Sudan just south of Malakal and contributes an average annual flow of 13.5 BCM in average. 3.2 The Blue Nile River The Blue Nile River initiates from Lake Tana in the Ethiopian highlands. The river at the outlet from the lake has an average annual flow of about 4 billion cubic meters. Many tributaries joining the Blue Nile throughout its course in Ethiopia. Two of these tributaries which have their main catchments lies in Ethiopia, namely Dinder and Rahad, join the Blue Nile in the Sudan. The Blue Nile connects to the White Nile at Khartoum to form the Main Nile and contributes with an average annual flow of 54 BCM. 3.3 The Atbara River The Atbara River is known as Tekezze in Ethiopia. It joins the Nile River at Atbara town in the Sudan and brings in average an annual flow of 12 BCM into the Nile. The Blue Nile and the Atbara rivers obtain most of their annual flow during the three months between mid-June and mid-September. Their flows are therefore torrential with heavy loads of silt. The fertile Nile delta in Egypt has been formed because of the silt carried down mostly by these two rivers. 4. The Bahr el Ghazal Basin 4.1 The SUDD region basin and the White Nile Bahr el Ghazal receives its water from several rivers draining western and south-western South Sudan bordering Congo and the Central African Republic. Its catchment area is 526,000 km2 of which about 40,000 km2 is swamp. Almost all of the inflow to Bahr el Ghazal from tributary rivers and direct rainfall on the swamp is lost and the remainder is only about half a billion cubic meters of water per year reaching the White Nile at Malakal. 6 Considering this little contribution of water (i.e. 0.5 BCM) from the Bahr el Ghazal basin, the total flow from the Sudd region to the White Nile at Malakal is about 15.5 BCM per year. Therefore, the average annual flow of the White Nile at Malakal which is considered as the northern end of the Sudd region can be summarized as follows: Contribution from Bahr el Jebel and Zeraf 15.00 x 109 m3/year Contribution from Bahr el Ghazal 0.50 x 109 m3/year Contribution from Sobat River 13.50 x 109 m3/year Total flow of White Nile at Malakal 29.00 x 109 m3/year 5. The Main Nile River: Starting from Khartoum in Sudan, the river is known as the Main Nile up to its mouth into the Mediterranean Sea. The Main Nile has a length of approximately 3065 km. The average annual amount of water estimated is at Aswan at about 84 BCM. If we divide this annual yield into water units each of them is 12 BCM, the annual yield at Aswan would be composed of 7 units. The quantity of water of the various tributaries at selected points are as shown in the following summary and figure (3): Bahr el Jebel downstream L. Albert 2 units Bahr el Jebel downstream the Sudd 1 unit Sobat River 1 unit White Nile 2 units Blue Nile River 4 units Atbara River 1 unit Main Nile at Aswan 7 units 7 Figure (3) A Sketch Showing the Nile Yield from Different tributaries