Blue Nile
The Blue Nile ( Arabic النيل الأزرق, DMG an-nīl al-azraq , Amharic ዓባይ Abbai , English Blue Nile , Abbay or Abay ) is next to the White Nile one of the two main strands in the river system of the Nile . It runs through Ethiopia and Sudan . Even if its water flow is on average larger than that of the White Nile, it is now regarded as the largest tributary of the Nile and less as an equal source river. Unlike the Blue Nile, the White Nile is the central drainage line of the catchment area .
Surname
The name is an imprecise translation of the Arabic word Azraq , which means dark as well as blue . The dark color of the Blue Nile is caused by the fine-grained soil material from the Abyssinian highlands of Ethiopia , which is carried in large quantities as suspended cargo . The suspended solids that are carried along make the Blue Nile a white water river .
course
The Blue Nile (Amharic: Abbai ) rises as Gilgel Abay (Little Abbai) near Gish Abay at an altitude of about 2728 m . It flows mainly in a northerly direction and flows into Lake Tana, which is 1786 m high . The Blue Nile is the only natural outflow that leaves it at the Chara-Chara weir near the city of Bahir Dar in a south-easterly direction. Since the commissioning of the Tana Beles power plant in 2010, Lake Tana has had another outflow through this power plant into the Beles , which flows into the Blue Nile just before the Sudanese border.
About 30 km after leaving Lake Tana, the Blue Nile tumbles down the Tisissat waterfalls and begins to flow in gorges that are up to 1,200 m deep and only end after almost 800 km at the Sudanese border. These inaccessible gorges are still a difficult traffic obstacle to overcome. In them the Blue Nile flows first to the southeast, then to the south and finally to the northwest.
In Sudan the Blue Nile first flows through low hills and then meanders through the Jazira plain until it joins the White Nile to form the Nile immediately after Khartoum and the opposite al-Chartum Bahri near Omdurman .
Different information is given about the length of the Blue Nile, ranging from 1,783 km over 1,600 km up to 1,450 km.
Water data
The Blue Nile gets its water from the mountains of the Abyssinian highlands , i. H. from the catchment area of Lake Tana and from the mountainous region which it then crosses. The water flow is largely dependent on the rainy season between June and September. At this time the Blue Nile carries up to sixty times as much water as in the dry season and transports a high proportion of sediments. With some time lag, this flood arrives in Sudan and Egypt, where it used to be of fundamental importance for agriculture as a flood of the Nile with its fertile Nile mud . Since the construction of the Aswan High Dam and other changes, the Nile flood has only played a minor role. The water flow of the Blue Nile can fluctuate strongly from year to year, on average the Blue Nile contributes about 69% to the water flow of the Nile.
The flow rate of the river was measured for 70 years (1912–1982) at the Roseires Dam gauge, at around 2/3 of the catchment area, in m³ / s. The water flow decreases in the further course due to irrigation and evaporation. In addition, the Blue Nile receives hardly any more water until it confluences with the White Nile in arid Sudan, especially since a great deal is taken from the region for irrigation of agriculture .
use
The use of the Blue Nile in Ethiopia is particularly hindered by the inaccessibility of the Abay gorges and the low level of traffic in the highlands. After the two small Tis Abay power plants , which only generate electricity , the Angereb Reservoir above Lake Tana was only built to supply the city of Gonder with water . The Fincha power plant in a side valley of the Abay is used for both electricity generation and irrigation, as is the Tana Beles power plant , which went into operation in 2010, at an artificial outlet of Lake Tana. The Fincha power plant in particular largely avoids the problem of sedimentation by drawing its water from a lake above it in the highlands, which hardly contains any suspended matter.
The Grand Ethiopian Renaissance dam , which has been under construction since 2011, is not only located in an inaccessible area just before the Sudanese border, far away from larger customers. As one of the largest hydropower projects in Africa, it will be able to control the volume of water flowing off the Blue Nile, which, as the largest tributary of the Nile, has an impact on the Lake Nasser formed by the Aswan Dam and thus on the total amount of water available for Egypt.
In Sudan, the water of the Blue Nile is mainly used for irrigation and, to a lesser extent, for generating electricity . This applies in particular to the Jazira project , which has been expanded several times and was irrigated by the Sannar Dam from 1925 , as well as to the adjacent al-Managil expansion and the Rahad project on the right bank of the river, which has had its water from the Roseires Dam since 1966 receive. The volume of both reservoirs was reduced by the very high sedimentation carried by the Blue Nile. The reservoirs are therefore emptied annually via the bottom outlet of the dams in order to flush out the sedimentation as much as possible.
Conflicting interests
The Nile is literally vital to Egypt, which has virtually no other fresh water. For this reason, Egypt has long taken the position that nobody should interfere with the inflow, especially from the Blue Nile. During the time of British rule in Egypt and Sudan , treaties were made expressing this. In the 1902 treaty between the United Kingdom, representing Egypt and the Sudan, and the Abyssinian Empire to define their common borders, Emperor Menelik II declared that he would not allow any construction that would affect the river without the consent of the British and Sudan. In the 1929 treaty between the still British-dominated Egypt and the Anglo-Egyptian Sudan, represented by the British, the natural and historical right of Egypt over the water of the Nile was affirmed and any influence on the amount of water without the consent of Egypt was excluded. In 1959 the independent countries Egypt and Sudan agreed a certain amount of water reserved for Sudan, whereupon Sudan approved the Aswan High Dam and the Lake Nasser, which extends far into Sudan . The significance of these contracts is highly controversial on the part of the other neighboring countries. With this contractual situation, it was hardly possible for Ethiopia to find sponsors for dam and power plant projects, especially during the Cold War .
For Ethiopia, for example, there is the paradoxical situation that although more than 80% of the Nile water for Egypt comes from the country (together with the Atbara ), the water-rich, but poor state itself should refrain from extensive use of the Nile. Ethiopia tries through diplomatic channels to assert its water needs and to achieve cooperative solutions with Egypt within the mechanisms of the Nile Basin Initiative (NBI for short) founded in 1998 . Ethiopia currently only uses around 1% of the water in the Nile. On the Ethiopian side, the Grand Ethiopian Renaissance Dam , which Egypt opposes, has been under construction since 2011 .
history
The first European to discover the sources of the Blue Nile or Gilgel Abay was Pedro Páez (1564–1622), a Jesuit missionary working in Ethiopia , who in 1613 traveled from Lake Tana to the sources. His history of Ethiopia ( História da Ethiópia ) remained unpublished, so that his discovery was forgotten again. Other Europeans living in Ethiopia are likely to have seen Lake Tana and the river (but not its sources) before him, such as the Portuguese explorer Pêro da Covilhã (1450–1530) or João Bermudes , who posed as the Patriach of Ethiopia and published in his 1565 Memoirs first reported from the Tisissat waterfalls. The Portuguese Jesuit and explorer Jerónimo Lobo (1593–1678) visited and described the sources in 1622. The Scottish African explorer James Bruce (1730–1794) saw them again in 1770 during his two-year stay in Gonder.
The course of the Abay below the waterfalls with its deep gorges and raging rapids remained unexplored until the 20th century. Attempts to navigate it ended after just a few kilometers, for example in 1902 the company of the American WW Macmillan and the Norwegian BH Jenssen, who planned to navigate the river separately and meet in the middle. Major Cheesman succeeded in exploring the course in the years 1925–1933 by repeatedly advancing to the edge of the gorges on foot or with mules from the highlands and thus covering around 8000 km. In 1930 an airplane used the Blue Nile for orientation on the flight from Addis Ababa to Khartoum. In 1954 Herbert Rittlinger and his wife Marianne tried to cross the river with folding boats from Lake Tana, but soon had to give up because of attacks by crocodiles. In 1962 A. Amoudruz and five other members of the Canoe Club de Genève drove a long distance below the Abay Bridge, but were then attacked by bandits who shot two of the group. In 1965 the Swede Arne Rubin managed to go from the bridge in a kayak to Khartoum in nine days despite various crocodile attacks. However, he lost his equipment with camera, films and notes in one of the last rapids.
The first complete traverse was made by John Blashford-Snell and his Great Abbai Expedition in 1968. At the request of Emperor Haile Selassie , he assembled a team of 60 British and Ethiopian soldiers and scientists and had specially constructed boats built for his expedition into the Blue Nile drove through two sections to the Sudanese border.
Attractions
30 km south of Bahir Dar is the village of Tis Issat and the Tisissat waterfalls. Here the Blue Nile plunges 42 meters into the depth. With a width of over 400 meters during the rainy season, it is the second largest waterfalls in Africa. They consist of four adjoining main fall areas. The Tisissat waterfalls are considered to be one of the main tourist attractions of Ethiopia. However, they have been severely affected since large amounts of water have been channeled past the falls through the nearby Tis Abay power plants and since 2010 water has been flowing from Lake Tana to the Tana Beles power plants.
See also
- List of bridges over the Nile
- List of dams on the Nile
- List of waters in Sudan
- List of the longest rivers on earth
- List of rivers in Ethiopia
literature
- Travel reports
- Hermann von Pückler-Muskau : From Mehemed Alis Reich , 3 vols., Stuttgart: Hallberger 1844; ND in 1 volume with commentary and notes. Zurich: Manesse 1985
- Kuno S. Steuben : On the gold sources of the pharaohs: Alone on the raging Nile , Ullstein, Berlin / Frankfurt / Vienna 1963
- Rüdiger Nehberg : Adventure Adventure: Blue Nile and Rudolfsee. Kabel, Hamburg 1982, ISBN 3-921909-61-9
- Virginia Morell : The Blue Nile: A Inflatable Boat Expedition on Ethiopia's Mysterious River , Goldmann, 2002, ISBN 9783442711857
- Foreign language
- Robert Ernest Cheesman Lake Tana and the Blue Nile: An Abyssinian Quest. Macmillan and Co., Limited, 1936.
- Herbert Rittlinger: Black Adventure. From the Red Sea to the Blue Nile. FA Brockhaus, Wiesbaden 1955
- Arne Rubin, Ensam med Blå Nilen, Forum 1966
- Richard Snailham: The Blue Nile Revealed: The Story of the Great Abbai Expedition , Chatto & Windus, 1970, 2nd edition 2005 in the Google book search
- Alan Moorehead: The Blue Nile , revised edition, Harper and Row, New York 1972
- Richard Bangs / Pasquale Scaturro: Mystery of the Nile , New American Library, New York 2005
Web links
- Yacob Arsano: Ethiopia and the Nile. Dilemmas of National and Regional Hydropolitics. Diss. ETH Zurich, Center for Security Studies, 2007
Individual evidence
- ↑ a b Development and Management of Irrigated Lands in Tigray, Ethiopia Eyasu Yazew Hagos, 2005, page 39 (sheet 57), on: edepot.wur.nl (pdf)
- ↑ a b Hydrologic impacts of Landuse change in the Upper Gilgel Abay River Basin, Ethiopia Webster Gumindoga, 2010, page 6 (sheet 19), on: itc.nl (pdf; 3.0 MB)
- ↑ The source height is taken from Google Earth
- ↑ a b Bridges over the Nile in Khartoum / Sudan Dipl.-Ing. Gregor Gebert and Dr.-Ing. Andreas Reichelt, 2010, page 6, on: vsvi-mv.de (pdf; 14.2 MB)
- ↑ GRDC - Khartoum gauge
- ↑ a b GRDC data for the Roseire level . The flow of the level below Khartoum is lower due to evaporation losses (MQ: 1513 m³ / s).
- ^ Henri J. Dumont: The Nile: Origin, Environments, Limnology and Human Use . Monographiae Biologicae, Vol. 89, Dordrecht 2009 ISBN 1402097263
- ↑ The length information usually leaves open whether the Gilgel Abay was included and how the constantly changing meanders were measured. In addition, the inaccessible gorges in Ethiopia may not have been precisely measured to this day.
- ^ A b Greg Shapland: Rivers of Discord: International Water Disputes in the Middle East. C. Hurst & Co., London 1997, ISBN 1-85065-214-7 , p. 67
- ↑ Arthur Okoth-Owiro: The Nile Treaty. Konrad Adenauer Foundation, Nairobi 2004
- ↑ a b Richard Snailham: The Blue Nile Revealed: The Story of the Great Abbai Expedition , Chatto & Windus, 1970, 2nd edition 2005 in the Google book search
- ↑ according to rastlos.com