Kariba Dam in Central Africa - Essay Example

?Kariba Dam, Central Africa Introduction: Kariba dam is a truly hydroelectric dam and an only truly international water resource project situated in the Zambezi river basin. It was constructed jointly by the governments of two countries, Zambia and Zimbabwe, in the year 1958 and is one of the major producers of power in Southern African region, with a capacity of approximately 1.3 GW. It is also one of the oldest and largest dams in the world, which is approximately 128 m (420 ft) tall and 579 m (1900 ft) long. It is shared by two countries, and is built on an international river which involves as many as nine countries and hence offers valuable lessons with regard to the establishment, application and maintenance of inter-country dam projects (Jobin, 1999: 421). Figure 1: Kariba Dam on the Zambezi river: Zambia/ Zimbabwe Source: http://www.internationalrivers.org/es/kariba-dam/kariba-dam?size=_original Furthermore it also offers valuable lessons in the manner in which a project of such huge magnitude was pulled off successfully in those days, considering the situation in the 1950s. Also, the construction of this dam required displacement of a large number of people living in or near by the dam site, thus attracting various social repercussions in the process (Adey, 2009: 116). The various implications of the establishment and implementation of this project are discussed in the following sections. Geological Setting The Kariba Dam is a double curvature arch concrete dam, reinforced with a spillway gate area (Balon & Coche, 1974). The Zambezi river, prior to reaching Lake Kariba, falls into various slot like gorges, which forms the Victoria falls. The drainage basin of the Congo River lies to the north of Zambia. Topographically, a significant portion of the Zambian territory comprises of an elevated plateau with an altitude of approximately 3000 to 4500 feet. There are highlands in the northeast and northwest territories of the country, with the Muchinga Mountains in the northwest having elevations of approximately 5900 feet. The population centres in Zambia are formed of two key areas, i.e. in the capital city of Lusaka and in the copper belt province of north central Zimbabwe, which comprise of rich deposits of copper ore (Stokes, 2009:751). Figure 2: Physical characteristics of Kariba Dam The soil in the Kariba river basin is deep Kalahari sand formation (Bingham, 2000) thus allowing the water to permeate in it quite easily. This is known to be one of the key reasons behind the occurrence / or high incidence of earthquakes in the area. Since the land was filled with excessive weight (i.e. water) the earth below it breaks down due to the added volume, leading the ground to break. There is evidence relating the level of artificially created lakes and seismic activities in the area, leading to increased incidences of earthquakes (Jansen, 1988: 744; Goudie & Alexander, 1997: 40). The dam was initially built with a view to generate hydroelectric power; however, the creation of the same drastically altered the geography of the land including significant changes and alterations to the biodiversity of the neighbouring areas. The Kariba Lake was located in the tropics and was one of the first projects to be built in the region. It was created by damming of the Zambezi River which flowed between the two countries i.e. Zambia and Zimbabwe in the year 1959. The building of this lake was referred to as an audacious engineering feat since it was created by clearing up a large proportion of the lands leading to displacement of thousands of locals (Gray, 2000:69). Major problems encountered The construction of the Kariba dam brought about significant changes in the area, especially the generation of electricity which was the key purpose behind the dam. However, it also led to several problems which are discussed below: Displacement of large number of people: The creation of the dam required displacement of the Tonga tribesmen, who inhabited the area. As many as 75000 tribal people were relocated to other areas during the construction of the dam. According to Takeuchi (1998: 20) the creation of artificial / man-made lakes entails displacement of large number of people leading to immense economic, psychological, social as well as cultural problems. The displaced communities are often relocated to less fertile lands where they overuse the available resources thus jeopardizing the environmental sustainability ultimately leading to adverse negative impacts. Ecological damage: Due to the construction of the dam, a large amount of plains / land in the area was cleared for the purpose. The area comprised of densely vegetated flood plains, in the Barotse and Chobe regions in Upper Zambezi and Kafue Flats. These areas form the major wetlands and acted as a refuge for important wildlife especially fish, avifauna and other water dependent mammals such as hippopotamus and lechwe and sitatunga antelopes. However, post the construction of the dam, significant changes in the ecology were observed in the Zambezi River system (Gupta, 2007: 320). Environmental Impacts: The Mid Zambezi area was a typically sand bank river, prior to the Kariba project. However, post the construction, and the immense changes made to the area to make way for the dam, it was observed that the fertility had dropped significantly, which was mostly attributed to the replacement of the perennial grasses (Jackson, 1961). Health Hazards The tampering of the site of construction may disrupt the ecological balance leading to increased incidences of natural disasters such as earthquakes and floods. The same could lead to endangering the lives of those living around the regions. Furthermore, floods may cause outbreak of epidemics such as plague, leading to further loss of lives and an increased cost to the administration. Remedial Measures taken Efforts were made to rescue those who were likely to be impacted by the floods. The tribal people were intimated to dislocate to safer areas while the animals and livestock were transported to safety. Furthermore, attempts are being made to restore and encourage the economic activities in the valley, which are funded not by the governments, but mostly through donations. Although no efforts have so far been made to help support the thousands of tribesmen who were dislocated from the site, with regard to helping them settle or engaging them in meaningful employment. As a part of its safety measures, the authorities conduct bi annual inspections and surveys on the Dam and a safety inspection is carried out after every five years where the help is sought from international experts, from engineering companies in France and UK, who were involved in the original design team. Furthermore, various other ad hoc inspections are carried out from frequently. Annual maintenance with regard to spill gates and stop locks are also undertaken annually. Also, various instruments are attached to the wall for measuring stress or any slight change in the movement in the wall due to water pressure or for detecting any sign of leakage. Such changes are constantly monitored (spurwingisland, 2011). Also, significant steps are taken to ensure that the storage levels of the lake are maintained at all times. As the land on which the lake is built is highly susceptible to earthquakes, it is of utmost importance to maintain the lake levels to stabilize the pressure. The inflows of water in the dam occur during the months of March to May, which are the rainy seasons. During this period, the flows from the two catchment areas fill up the Kariba lake, i.e. one from the upper catchment area in Angola / Zambia and the other from the lower catchment area in Zambia / Zimbabwe. The Kariba dam faces no imminent danger from the inflows, as it was built to withhold maximum capacity. The spill rate per floodgate of this dam is 1500 cubic meters per second. Technically the spill capacity of each of the spill gates of the dam are designed to spill approximately 9000 cumecs however, the dam is known to spill a record of 16000 cumecs during the 1956 flood, thus signifiying its capacity and strength. Also, the Zambezi River Authority finds it prudent to control the water-level at a maximum operating level of 1 meter below the danger level to prevent overtopping and other sequential damages. Thus although the dam has about 6 flood gates the authorities, prefer to restrict the spill by utilizing only 3 flood gates. The lake levels are carefully monitored and calculated during the rainy season, to ensure the storage capacity and prior warnings are given in case of floods (spurwingisland, 2011). Lessons Learned On the basis of the above discussion, the key lessons learned include: the need and significance of detailed pre-construction inspection of the geology and topography of the dam site and a study of the various key features of the surrounding area; the construction of large man-made reservoirs of huge magnitude always entail significant changes in the seismic activity, leading to long term damage to the life as well as property; the construction of artificial lakes and dams, bring about changes in the ecology as well as the ecosystem altering their normal manner of functioning, thus leading to large scale environmental damages; the reservoirs can also lead to various benefits such as production of large amount of power; forced relocation of the locals from the site may lead to a series of social, economic as well as psychological damage and addressing the same must be the top priority of the administration. Appendices: Source: Chenje and Johnson, 1996: xiv Figure showing the different rock types in the Kariba Dam area Source: http://www.mme.gov.na/gsn/posters/earth%20science/5_Lake_Kariba.pdf References: Adey, P., (2009). Mobility, Taylor & Francis Publication, Pp. 116-117 Balon, E. K., Coche, A. G., (1974). Lake Kariba: a manmade tropical ecosystem in Central Africa. Junk, The Hague, Pp. 767 Chenje, M., & Johnson, P. (1996). Water in southern Africa. Maseru/Harare: SADC/IUCN/SARDC Gray, W., (2007). Zambia and Victoria Falls, New Holland Publishers, Pp. 69-70 Goudie, A., Alexander, D. E., (1997). The human impact reader: Readings and case studies, Wiley-Blackwell Publication, Pp.40 Gupta, A., (2007). Large rivers: geomorphology and management, John Wiley & Sons, Pp. 320 Jansen, R. B., (1988). Advanced dam engineering for design, construction, and rehabilitation, Springer Publication. Pp. 744 Jackson, P. B. N., (1961). The fish of the middle Zambezi, Kariba studies. Manchester University Press Jubin, W. R., (1999). Dams and disease: ecological design and health impacts of large dams, canals and irrigation systems, Taylor & Francis publication, Pp. 421-422 Stokes, J., (2009). Encyclopedia of the People's of Africa and the Middle East: Vol. 1, Infobase Publishing, Pp. 751 Takeuchi, K., (1998). Sustainable reservoir development and management, Inernational Association of Hyrological Sciences, Pp. 20 spurwingisland.com (2011). [Online] Available at: http://www.spurwingisland.com/news-detailed.html?newsdet:ncode=2 [Accessed: May 17, 2011] Read More