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Akosombo Dam

Akosombo Dam
File:Akosombo Dam from the Volta Hotel.JPG
Akosombo Dam as seen from the Volta Hotel
Location of the Akosombo Dam in Ghana
Location Akosombo, Ghana
Coordinates

6°17′59″N 0°3′34″E / 6.29972°N 0.05944°E / 6.29972; 0.05944Coordinates: 6°17′59″N 0°3′34″E / 6.29972°N 0.05944°E / 6.29972; 0.05944{{#coordinates:6|17|59|N|0|3|34|E|region:GH_type:landmark |primary |name=

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Status Operational
Construction began 1961
Opening date 1965
Construction cost £130 million
Owner(s) Volta River Authority
Dam and spillways
Type of dam Embankment, rock-fill
Impounds Volta River
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Dam volume Script error: No such module "convert".
Spillways Twin gate-gontrolled
Spillway capacity Script error: No such module "convert".
Reservoir
Creates Lake Volta
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Power station
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Turbines 6 x Script error: No such module "convert". Francis-type
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Website
www.vra.com/our_mandate/akosombo_hydro_plant.php

The Akosombo Dam, also known as the Akosombo Hydroelectric Project, is a hydroelectric dam on the Volta River in southeastern Ghana in the Akosombo gorge and part of the Volta River Authority. The construction of the dam flooded part of the Volta River Basin, and led to the subsequent creation of Lake Volta. Lake Volta is the largest man-made lake in the world by surface area. It covers Script error: No such module "convert"., which is 3.6% of Ghana's land area. With a volume of 148 cubic kilometers Lake Volta is the world's third largest man-made lake by volume, the largest being Lake Kariba which is located between Zimbabwe and Zambia in Southern Africa and contains 185 cubic kilometers of water.[1]

The primary purpose of the Akosombo Dam was to provide electricity for the aluminium industry.[2] The Akosombo Dam was called "the largest single investment in the economic development plans of Ghana."[3] Its original electrical output was Script error: No such module "convert"., which was upgraded to Script error: No such module "convert". in a retrofit project that was completed in 2006.[4]

The flooding that created the Lake Volta reservoir displaced many people and had a significant impact on the environment.[5]

History

File:Akosombo Dam is spilling water, Ghana.JPG
Akosombo dam with open spillways

The dam was conceived in 1915 by geologist Albert Ernest Kitson, but no plans were drawn until the 1940s.[6] The development of the Volta River Basin was proposed in 1949, but because there were insufficient funds, the American company Volta Aluminum Company (Valco) loaned money to Ghana so that the dam could be constructed. Kwame Nkrumah adopted the Volta River hydropower project.[3]

The final proposal outlined the building of an aluminum smelter at Tema, a dam constructed at Akosombo to power the smelter, and a network of power lines installed through southern Ghana. The aluminum smelter was expected to eventually provide the revenue necessary for establishing local bauxite mining and refining, which would allow aluminum production without importing foreign alumina. Development of the aluminum industry within Ghana was dependent upon the proposed hydroelectric power.[3] The proposed project's aluminum smelter was overseen by the American company, Kaiser Aluminum, and is operated by Valco. The smelter received its financial investment from Valco shareholders, with the support of the Export-Import Bank of Washington, D.C. However, Valco did not invest without first requiring insurances from Ghana's government, such as company exemptions from taxes on trade and discounted purchases of electricity. The estimated total cost of the project, in its entirety, was estimated at $258 million.[3]

In May 1960, the Ghana government called for tenders for construction of the hydroelectric dam. In 1961 an Italian consortium, Impregilo which had just completed the Kariba Dam, won the contract. They carried out the dredging of the river bed, dewatering of the channel and completed the dam a month earlier than scheduled despite flooding of the Volta River in 1963 which delayed work for over three months. Between 1961 and 1966, 28 workers of Impregilo died during the construction of the dam. Memorials in Akosombo township and St. Barbara Catholic Church have been put up in their honor.

In 1961, the Volta River Authority (VRA) was established by Ghana's Parliament through the passage of the Volta River Development Act. The VRA's fundamental operations were structured by six Board members and Kwame Nkrumah as chairman. The VRA's primary task is to manage the development of the Volta River Basin, which included the construction and supervision of the dam, the power station and the power transmission network. The VRA is responsible for the reservoir impounded by the dam, the fishing within the lake, lake transportation and communication, and the welfare of those surrounding the lake.[1]

The dam was built between 1961 and 1965.[7] Its development was undertaken by the Ghanaian government and funded 25% by the International Bank for Reconstruction and Development of the World Bank, the United States, and the United Kingdom.[8]

The construction of the Akosombo dam resulted in the flooding of part of the Volta River Basin and its upstream fields, and in the creation of Lake Volta which covers 3.6% of Ghana's total land area.[1] Lake Volta was formed between the years of 1962 and 1966, and necessitated the relocation of about 80,000 people, that represented 1% of the population.[9] People of 700 villages were relocated into 52 resettlement villages two years prior to the lake's completion; the resettlement program was under the direction of the VRA.[1][2][5] Two percent of the resettlement population were riparian fishers and most were subsistence farmers.[2] The Eastern Region of Ghana and the populations incorporated within its districts, were most subject to the project’s effects.[10]

In the beginning of 2007, there were concerns over the electricity supply from the dam due to low water levels in the Lake Volta reservoir.[11] Some sources said this was due to problems with drought that are a consequence of global warming.[12] During the latter half of 2007 much of this concern was abated when heavy rain fell in the catchment area of Volta River.[13] In 2010 the highest ever water level was recorded at the dam. This necessitated the opening of the flood gates at a reservoir elevation of Script error: No such module "convert"., and for several weeks water was spilled from the lake causing some flooding downstream.[14]

Design

The dam is a Script error: No such module "convert". long and Script error: No such module "convert". high rock-fill embankment dam. It has a base width of Script error: No such module "convert". and a structural volume of Script error: No such module "convert".. The reservoir created by the dam, Lake Volta, has a capacity of Script error: No such module "convert". and a surface area of Script error: No such module "convert".. The lake is Script error: No such module "convert". long. Maximum lake level is Script error: No such module "convert". and minimum is Script error: No such module "convert"..[7] On the east side of the dam are two adjacent spillways that can discharge approximately Script error: No such module "convert". of water. Each spillway contains six Script error: No such module "convert". wide and Script error: No such module "convert". tall steel floodgates.[15][16]

Akosombo Power Station

The dam's power plant contains six Script error: No such module "convert". Francis turbines. Each turbine is supplied with water via a Script error: No such module "convert". long and Script error: No such module "convert". diameter penstock with a maximum of Script error: No such module "convert". of hydraulic head afforded.[7]

Power distribution

The dam provides electricity to Ghana and its neighboring West African countries, including Togo and Benin. Initially 20% of Akosombo Dam's electric output (serving 70% of national demand) was provided to Ghanaians in the form of electricity, the remaining 80% was generated for the American-owned Volta Aluminum Company (VALCO). The Ghana Government was compelled, by contract, to pay for over 50% of the cost of Akosombo’s construction, but the country was allowed only 20% of the power generated. Some commentators are concerned that this is an example of neocolonialism. In recent years the production from the VALCO plant has declined with the vast majority of additional capacity in Akosombo used to service growing domestic demand.[17]

Impacts

File:Akosombo Dam hydroelectric plant.jpg
The hydroelectric power plant on Lake Volta

The Akosombo Dam benefited some industrial and economic activities from the addition of lake transportation, increased fishing, new farming activities along the shoreline, and tourism.[5] The power generated has provided for primary interests within Ghana, while also supplying power to the neighboring countries of Togo and Benin.[10] Ghana’s industrial and economic expansion triggered a higher demand for power, beyond the Akosombo's power plant capabilities. By 1981, a smaller dam was built at the town of Kpong, downstream from Akosombo and further upgrades to Akosombo have become necessary for maintaining hydropower output.[1] Initially, the dam’s power production capabilities greatly overreached the actual demand; while, the demand since the dam’s inception has resulted in the doubling of hydropower production.[18] Increasing demands for power exceed what can be provided by the current infrastructure. Power demands, along with unforeseen environmental trends, have resulted in rolling blackouts and major power outages.[1][18] An overall trend of lower lake levels has been observed, sometimes below the requirement for operation of the Akosombo Dam.[18]

Biological habitat

In the time following the construction of the dam at Akosombo, there has been a steady decline in agricultural productivity along the lake and the associated tributaries.[5] The land surrounding Lake Volta is not nearly as fertile as the formerly cultivated land residing underneath the lake, and heavy agricultural activity has since exhausted the already inadequate soils. Downstream agricultural systems are losing soil fertility without the periodic floodings that brought nutrients to the soil before the natural river flow was halted by the dam.[18] The growth of commercially intensive agriculture has produced a rise in fertilizer run-off into the river. This, along with run-off from nearby cattle stocks and sewage pollution, has caused eutrophication of the river waters.[5] The nutrient enrichment, in combination with the low water movement, has allowed for the invasion of aquatic weeds (Ceratophyllum). These weeds have become a formidable challenge to water navigation and transportation.[1]

Human welfare

The presence of aquatic weed along the lake and within the tributaries has resulted in even greater detriment to local human health. The weeds provide the necessary habitat for black-fly, mosquitoes and snails, which are the vectors of water-borne illnesses such as bilharzia, river blindness and malaria.[5] Since the installment of the dam, these diseases have increased remarkably. In particular, resettlement villages have showed an increase in disease prevalence since the establishment of Lake Volta, and a village’s likelihood of infection corresponds to its proximity to the lake.[2] Children and fishermen have been especially hard hit by this rise of disease prevalence.[2] Additionally, the degradation of aquatic habitat has resulted in the decline of shrimp and clam populations.[1] The physical health of local communities has been diminished from this loss of shellfish populations, as they provided an essential source of dietary protein. Likewise, the rural and industrial economies have experienced the financial losses associated with the decimation of river aquaculture.[5]

Socioeconomics

The loss of land experienced by the 80,000 people forcibly relocated meant the loss of their primary economic activities from fishing and agriculture, loss of their homes, loss of their family grave sites, loss of community stability, and the eventual loss of important social values.[5] The resettlement program demonstrated the social complexities involved in establishing “socially cohesive and integrated” communities.[5] Insufficient planning resulted in the relocation of communities into areas that were not capable of providing for their former livelihoods and traditions.[5] The loss of the naturally fertile soils beneath Lake Volta essentially led to the loss of traditional farming practices.[5] The poor living conditions provided within the resettlement villages has been demonstrated by population reductions since resettlement. One resettlement village in particular experienced a greater than 50% population reduction in the 23 years following relocation.[5] Increased economic risks and experiences of poverty are associated with those communities most impacted by the Volta River’s development.[1] The extensive human migration and degradation of natural resources within the Volta-basin area, are the products of poverty in conjunction with population pressure.[18]

Disease

Increased human migration within the area has been driven by poverty and unfavorable resettlement conditions.[5][18] This migration enabled the contraction of HIV and has since led to its heightened prevalence within Volta Basin communities.[10] The districts of Manya Krobo and Yilo Krobo, which lie within the southwest portion of the Volta Basin, are predominately indigenous communities that have attained a disproportionate prevalence of HIV.[10] The situation underlines the strength of the local factors upon these districts. Commercial sex work was established in response to the thousands of male workers that were in the area for building the dam.[10] Ten percent of the child-bearing females from these two districts migrated out of their districts during this time.[10] In 1986, “90% of AIDS victims in Ghana were women, and 96% of them had recently lived outside the country”.[10]

The Akosombo Dam and other dams of the Volta River Hydro Development Project increased substantially the conditions for the spread of schistosomiasis.[19]

Physical environment

Reservoir-induced seismicity has been recorded due to the crustal re-adjustments from the added weight of the water within Lake Volta.[5] There is an eastward shift of the river’s mouth from the changes to the river’s delta zone and this has led to continuing coastal erosion. The changes in the river hydrology have altered the local heat budget which has caused microclimatic changes such as decreasing rain and higher mean monthly temperatures. All of these larger scale environmental impacts will all further compound the problems surrounding disruptions to local economic activities and associated, difficult human welfare conditions.[5] A case study by the International Federation of Surveyors has indicated that the dam has had a significant impact on the shoreline erosion of the barrier separating the Keta Lagoon from the sea. Dr. Isaac Boateng has calculated the reduction of fluvial sediment as being from 71 million m3/a[clarification needed] to as little as 7 million m3/a.[20]

See also

References

  1. ^ a b c d e f g h i Fobil 2003
  2. ^ a b c d e Zakhary 1997
  3. ^ a b c d "History of Akosombo dam". Ghana Home Page. Archived from the original on 16 May 2011. Retrieved 8 May 2011. 
  4. ^ "Akosombo Hydro Power Plant Retrofit". Volta River Authority. Archived from the original on 8 August 2007. Retrieved 2007-07-30. 
  5. ^ a b c d e f g h i j k l m n o Gyau-Boakye 2001
  6. ^ http://www.thestatesmanonline.com/pages/news_detail.php?newsid=8696&section=1 http://www.thestatesmanonline.com/pages/news_detail.php?section=9&newsid=9224
  7. ^ a b c "Akosombo Hydro Power Plant". Volta River Authority. Archived from the original on 21 April 2007. Retrieved 2007-03-26. 
  8. ^ Commonwealth Education
  9. ^ Matthew Davis (30 May 2003). "Eyewitness: Waking up to water crisis". BBC. 
  10. ^ a b c d e f g Suave 2002
  11. ^ "Akosombo Dam To Be Shut Down?". Ghana web. 28 March 2007. 
  12. ^ Boafo, Owusu Ansa (2007-06-29). "Politics of Akosmobo Dam in Ghana". 
  13. ^ "Flood destroys farmlands in Bongo District". 2007-08-29. 
  14. ^ "VRA ends spillage from Volta Dam". GhanaWeb. Retrieved 30 May 2011. 
  15. ^ "Akosombo Dam Brochure" (PDF). Volta River Authority. Retrieved 30 May 2011. 
  16. ^ "Annex 3" (PDF). Alterra. p. 46. Retrieved 30 May 2011. 
  17. ^ Kwame Okoampa-Ahoofe (2007-08-28). "NPP cuts sod for Bui Dam". Statesman online. 
  18. ^ a b c d e f Van De Giesen 2001
  19. ^ Drisdelle R. Parasites. Tales of Humanity's Most Unwelcome Guests. Univ of California press, 2010. p. 11f. ISBN 978-0-520-25938-6. 
  20. ^ Boateng, Isaac (2010). Spatial Planning in Coastal Regions: Facing the Impact of Climate Change. Copenhagen: International Federation of Surveyors. 

Bibliography

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External links