Tekeze dam

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Tekeze dam
Tekeze lake
Tekeze lake
Tributaries: Tekeze
Drain: Tekeze
Tekeze Dam (Ethiopia)
Tekeze dam
Coordinates 13 ° 20 '40 "  N , 38 ° 44' 43"  E Coordinates: 13 ° 20 '40 "  N , 38 ° 44' 43"  E
Data on the structure
Lock type: Arch dam
Construction time: 2002-2009
Height of the barrier structure : 188 m
Height of the structure crown: 1145 m
Crown length: 420 m
Crown width: 5.6 m
Base width: 28 m
Power plant output: 300 MW
Operator: EEPCo
Data on the reservoir
Reservoir length 70 kmdep1
Storage space 5,343 million m³
Total storage space : 9,310 million m³
Catchment area 30,390 km²

The Tekeze dam on the border between the Ethiopian administrative regions Amhara and Tigray has been the highest dam in Africa at 188 m since February 2009. It stands at an altitude of around 1000 m on the eastern slope of the Ras Daschän massif, the highest mountain in Ethiopia at 4533 m, and dams the Tekeze , a tributary of the Atbara , which flows into the Nile . Its height exceeds the 185 m high Katse Dam in Lesotho , but will in turn be exceeded by the Gilgel Gibe III dam, which is already under construction .

description

The Tekeze dam is primarily used to generate electricity. It has a catchment area of ​​30,390 km² with an average annual rainfall of 850 mm, which, however, is concentrated almost exclusively on the rainy season in July, August and September. The reservoir fills the narrow and winding mountain valley of the Tekeze over a length of 70 km. Its storage volume is a maximum of 9,310 million m³, of which 5,343 million m³ can be used to operate the power plant.

The double-curved concrete arch dam is 188 m high and has a crown length of 420 m. It is 28 m thick at the base and 5.6 m at the crown. The concrete work for the dam took 36 months. It has four lower outlet gates with a cross-section of 8 m × 5.6 m about halfway up .

From the 75 m high inlet structure, the water runs through pressure tunnels and a vertical pressure shaft to a cavern with 4 Francis turbines with an output of 75 MW each. The electricity in Mek'ele is fed into the Ethiopian power grid via an outdoor switchgear and a 105 km long high-voltage line .

Details from the construction process

Before the dam was built, a 40 km long access road had to be created. The river was then diverted into two tunnels with a diameter of 7.0 and 7.8 m and lengths of 430 and 370 m. In order to save costs, the tunnels were only dimensioned on the basis of the small amounts of water during the dry season. The originally planned larger tunnel cross-sections and wide discharge gates in the dam were dispensed with. Instead, the concrete work in the lower part of the dam was staggered in such a way that three concreting blocks were significantly lower than the others. During the flood period of 2006, the flood flowed over these deeper concreting blocks without causing any significant damage. For the flood period of 2007, two concreting blocks were left open in the now higher dam wall. As a result, the filling of the reservoir in front of the lower part of the dam, which initially served as a heavy-weight dam, could already begin while the concreting work continued. The next flood flowed for 81 days through the two concreting blocks and the small diversion tunnels, with up to 1,313 m³ / s pouring into the gorge below the dam. The surfaces of the concrete culverts suffered only slight damage from cavitation , which could be easily removed in the course of further work.

Thanks to these workflows, the filling of the reservoir could be completed much earlier than usual and electricity generation could start earlier.

Involved

In 1995 the location of the project was selected and the first plans were made. In 1998 the engineering office MWH began to revise these drafts and the planning for the dam. In 2002 it was announced that the state-run Ethiopian Electric Power Corporation (EEPCo) had awarded the contract for the project to a joint venture made up of several Chinese and an Ethiopian companies. This joint venture included Sinohydro - CWHEC , CGGC, China Wanbao Engineering Corp., JPPC and CCC. The turbine supplier was Dongfang. The losing bidders included Strabag, Salini Impregilo, Kajima, Enka and Skanska.

The estimated cost of the project (including planning, construction management, etc.) at US $ 365 million was allegedly fully financed by Ethiopia. However, some believe that cheap Chinese credit played a major role.

Ethiopia was able to inaugurate further hydropower plants in 2009/10 : Gilgel Gibe II with 420 MW and Tana Beles with 460 MW. Electricity that is not used in Ethiopia is to be exported to Djibouti.

See also

Web links

Individual evidence

  1. ↑ Photos of the flood flowing over the dam in Google Maps
  2. ↑ Tekeze Hydropower Project ( Memento from January 14, 2015 in the Internet Archive ) on the MHW website
  3. ↑ China Wins Contract to Build Another 'Three Gorges' Dam in Africa June 1, 2002 article on People's Daily Online
  4. ↑ James R. Stevenson, Ato Mihret Debebe: Hydro power in Ethiopia - the staged construction of Tekeze Arch Dam Article of May 11, 2009 in WaterPowerMagazine.com
  5. ↑ Ethiopia's Tekeze dam limps into operation article from November 2009 on Probe International