Cahora Bassa | dam and hydroelectric facility, Mozambique | Britannica.com dam and hydroelectric facility, Mozambique Written By: Alternative Titles: Cabora Bassa, Cabora Bassa Dam, Cahora Bassa Dam, Hidroeléctrica de Cabora Bassa Similar Topics Aswan High Dam Cahora Bassa, also spelled Cabora Bassa, arch dam and hydroelectric facility on the Zambezi River in western Mozambique . The dam, located about 80 miles (125 km) northwest of Tete, is 560 feet (171 m) high and 994 feet (303 m) wide at the crest. It has a volume of 667,000,000 cubic yards (510,000,000 cubic m). The dam impounds Lake Cahora Bassa , which is 150 miles (240 km) long and 19 miles (31 km) wide at its widest point.

The lake has a capacity of 51,075,000 acre-feet (63,000,000,000 cubic m) and extends to the Zambia-Mozambique border. The dam was built by a consortium of Portuguese, German, British, and South African companies; construction of the dam began in 1969 and was completed in 1974. The last of five 425-megawatt generators was installed in 1979. Cahora Bassa dam supplies power primarily to South Africa over an 870-mile- (1,400-kilometre-) long, dual 530-kilowatt transmission line and also to Maputo, Tete, and the Moatize coal mines near the town of Tete. Power transmission to South Africa was interrupted during the Mozambican civil war but resumed during the mid-1990s. The Companhia Hidroeléctrica de Cahora Bassa was owned by Portugal until 1992. Learn More in these related articles: Can This River Be Saved?

Rethinking Cahora Bassa Could Make a Difference for Dam–Battered Zambezi | International Rivers Can This River Be Saved? Rethinking Cahora Bassa Could Make a Difference for Dam–Battered Zambezi By: Date: Monday, February 1, 1999 Over the millennia, life in Southern Africa was measured by the ebb and flow of the great Zambezi River . Every year the river’s waters spilled over into its vast floodplains, irrigating subsistence crops, rejuvenating vital grasslands for wildlife and livestock, depositing nutrient–rich sediments in coastal mangroves, and triggering the lifecycles of countless species of plants and animals. Low dry–season flows sustained the productivity of coastal prawn fisheries and enabled the people of the river’s basin to harvest riverine fishes. For the past 40 years, however, the pulse of the Zambezi’s ancient flood cycle has been harnessed by the colossal Kariba and Cahora Bassa dams. Built with the promise that they would stimulate regional economic growth through hydropower production, these developments have come at great cost to the marginalized people and wildlife of the Zambezi basin.

Nowhere has this hardship been more pronounced than in the lower Zambezi valley of Mozambique. For twenty–five years, erratic and mistimed flooding below Cahora Bassa Dam has adversely affected the living standards of hundreds of thousands of downstream households and decimated one of the most productive and diverse wetland ecosystems in Africa, the Zambezi Delta. While Kariba was built before the impacts of dams were well–understood, Cahora Bassa has no such excuse – and in fact appears not to have incorporated many lessons from Kariba. The degree to which scientists’ concerns were ignored in the planning of the Cahora Bassa project is staggering. Before the dam was completed in 1975, South African river ecologist Dr.

Bryan Davies warned of the dam’s severe consequences in a pre–project assessment: "Reduced artisanal fisheries and shrimp industry productivity, reduced silt deposition and nutrient availability, severe coastal erosion, soil salinization, salt water intrusion, replacement of wetland vegetation by invasive upland species, reduction in coastal mangroves, failure of vegetation to recover from grazing, and disrupted or mistimed reproductive patterns for wildlife species." Just ten years later, deleterious changes to the Zambezi’s riverine, wetland, deltaic and coastal ecosystems were already apparent. Fisheries ecologists G. Bernacsek and S. Lopez lamented in a UN document, "It is clear that in the case of Cahora Bassa there was no serious attempt to ecologically optimize the dam prior to construction ... Cahora Bassa has the dubious distinction of being the least studied and possibly least environmentally acceptable major dam project in Africa." Now, a quarter century after the dam’s completion, the impacts predicted years ago have sadly come true. Except in years of exceptional local rainfall, the lower Zambezi River no longer overflows its banks at the time of natural peak flooding.

Most of the delta’s distributary channels are choked with invasive vegetation and no longer convey floodwaters to the desiccated floodplains. Anthropologist Dr. Ted Scudder notes that "villagers correctly attribute the loss of crucial land for grazing and flood recession agriculture, and a drop in the productivity to their fishery, to dam construction." Due to the lack of the natural seasonal variations in flow, the once lucrative delta prawn fishery has declined precipitously, and only one of the main channels of the Zambezi Delta mouth supports relatively healthy mangrove. According to Davies, "there are now large gaps in the mangrove forest along the entire northern and southern sectors that didn’t exist prior to 1975, and areas of coastal erosion with dead mangroves in evidence." Populations of Cape buffalo, waterbuck, reedbuck, zebra and hippo have declined by 95 percent or more as the now–dry floodplain has opened the area to commercial poaching. Grassland burning has intensified throughout the dry season, and more than 90 percent of the lower Zambezi floodplain now burns every year.

Research by Mozambican ornithologist Carlos Bento suggests that the breeding cycles of many delta species, including the endangered wattled crane, have been disrupted by the irregular flooding patterns below Cahora Bassa Dam. The devastation of the lower Zambezi seems all the more tragic in view of the fact that power lines were sabotaged shortly after the dam was completed. For more than 17 years, all but one of Cahora Bassa’s turbines remained idle while Mozambique’s civil war raged. Only in the past year has power production been restored to its original capacity. Restoring the Flood In 1995, a broad group of interested social and environmental scientists from Mozambique, South Africa, and North America joined together to promote the recovery of the lower Zambezi system through improved management of Cahora Bassa Dam. Through a series of comprehensive studies, this group began to assess the social, economic, and environmental advantages and disadvantages, for a broad range of stakeholders, of different strategies for managing Zambezi waters. These experts hoped to demonstrate that the "best" use of Zambezi waters requires the restoration of natural flooding patterns of the river through prescribed releases from Cahora Bassa Dam.

The benefits of prescribed flooding for downstream communities and ecosystems has gained worldwide attention in recent years. In the western United States, artificial flood releases from large dams are being tested to maintain instream flow requirements for riverine habitats, salmon fisheries, and recreational demands. In Africa, artificial flood releases below large dams are gaining acceptance as a means of promoting integrated rural development. In Nigeria, for example, artificial flood releases from the Tiga and Challawa Gorge Dams have been promising and could be used further to help restore the Komadugu–Yobe basin’s ecosystems. In the Senegal River basin, studies by the Institute for Development Anthropology have demonstrated that floodplain conditions below Manantali Dam would be improved with only a small reduction in hydropower, and that the cost of the lost hydropower is substantially outweighed by the economic benefits to agriculture and fisheries. From Cameroon to South Africa, experimental flood releases offer opportunities for reducing the damage in river basins that have been degraded by large dams. Indeed, African nations are leading the way in this emerging science.

Ideally, a prescribed flooding program for the lower Zambezi system would include the coordinated management of both Cahora Bassa and Kariba Dams (the latter controls more than 50 percent of the Zambezi catchment). Unfortunately, Kariba was designed with no consideration of prescribed water releases. Flood releases from Cahora Bassa Dam, however, are possible. Cahora Bassa’s eight sluice gates are located significantly lower on the dam wall than Kariba’s, and are below the average operating water level of the reservoir. Flood pulses have been released from Cahora Bassa Dam since its completion to prevent the dam from overtopping. These events were not planned, and thus took a heavy human toll because they occurred as flash floods. The 1978 flood wave alone killed 45 people, displaced more than 200,000, and destroyed nearly 60,000 hectares of crops. These floods did have unplanned benefits to the ecosystem, which has led scientists to believe that prescribed floods can play an important role in restoring ecological conditions in the lower Zambezi.

Following emergency flood releases from the dam in 1978, floodplain conditions improved dramatically for local flora and fauna. South African ecologist Paul Dutton observed that Cape buffalo and waterbuck populations increased markedly, and encroaching upland vegetation receded from the floodplain. In 1997, emergency flood releases again led to overbank flooding, and again the hydrological conditions in the lower Zambezi showed striking improvement. Waterbird populations increased and dispersed more widely, and the flushing of stagnant waterways in the floodplain led to an estimated 10–20 percent reduction in the cover of invasive plants. Political Realities Incorporating planned flood releases into the operation of Cahora Bassa Dam needs to be evaluated in light of a complex economic picture muddied by past debts and the effects of the long civil war. Mozambique is deeply in debt on the project to Portugal, its former colonial overseer (Portugal still owns 82 percent of the dam, and operates the dam through the firm Hidroelectrica De Cabora Bassa).

Because the Cahora Bassa debt is just one of the many burdens on Mozambique’s post–war economy, the government is pressed to generate maximum power output to eliminate the dam debt as quickly as possible. Although negotiations are underway to try to relieve some of the debt, Mozambique also remains bound by power contracts that date back to the 1970s and force the export of nearly all power from the dam. The encouraging news is that the Mozambican government is very enthusiastic about seeing improvements in the river’s ecosystem, and has been very interested in studies that will help it evaluate options to improve the dam’s management. One step it has taken is to look at the costs and benefits of an artificial flood on the dam’s income–generating capabilities. According to the Zambezi Valley Development Authority, the total value of contracts with South Africa and Zimbabwe for hydroelectric power from Cahora Bassa is about US$200 million per annum (based on about 2,100 megawatts of power). Preliminary hydrological studies suggest that management of outflows to mimic the historic mean annual Zambezi flood might entail, on average, a 10–15 percent reduction in hydropower output.

This would result in about $20–30 million in lost revenues per annum. The economic benefits of restoring natural flood cycles to the lower Zambezi derive from the anticipated improvements in downstream conditions. Although such gains can be difficult to quantify, the benefits to the coastal prawn industry alone are eye–opening. According to Mozambican fisheries ecologist Dr. Antonio Hoguane, "the lowering of dry–season flows and a rise in wet–season flows in the Zambezi River would stimulate recruitment of juvenile prawns to the population and improve production of the industry, leading to an increase in revenue of $10–$30 million per annum within two years of improved water management." Re–establishment of natural flood–release patterns would also have beneficial effects on the riverine fishery. Many fish species depend on overbank flooding to provide access to spawning grounds on the grassy floodplain, while lower dry season flows tend to improve the catch rate. Since Cahora Bassa Dam was built, local markets have experienced a significant decline in the quantity of large fish species taken from the lower Zambezi River. The annual value of improved flooding to the thousands of lower Zambezi fisherman would undoubtedly measure in the millions of dollars.

A more natural flood would also enhance the value of floodplain agriculture and grazing practices. Past studies by Swedish consultants argue that released floods would improve soil fertility, reduce salinity, increase the extent of flood recession cropping, and improve the species composition and carrying capacity of floodplains for native and domestic herbivores. These benefits are corroborated by findings from recent research in Senegal and Nigeria, which places the economic value of artificial flood releases for subsistence agriculture practices in the millions of dollars. Raising the carrying capacity of the Zambezi floodplain may also allow the once legendary concentrations of Cape buffalo, elephant, waterbuck, zebra, lion, and hippo to return. According to Dutton, restoration of healthy populations of Cape buffalo and other game species would result in substantial economic returns from tourism and regulated trophy– and food–hunting. Of course, economic analyses alone cannot begin to capture the full value of restoring the Zambezi ecosystem. The basin is of profound cultural and ecological importance to Mozambique and to the world. It is home to between 400,000–700,000 rural people, all of whom draw their livelihood from the river and its valley.

The lower Zambezi is of international importance for its diversity of mammal, fish, and waterbird species, many of which are endangered or vulnerable. It supports a rich mosaic of more than 12 different natural communities, including some of the most extensive coastal mangroves in Africa. It is the Zambezi river floodwaters that have created and maintained this richness. Further studies will provide a more complete accounting of these benefits, but clearly there are strong economic, social, and ecological arguments for restoring flooding to the lower Zambezi. The fate of the lower Zambezi ultimately depends on using these arguments to garner strong institutional support at the local, regional, national, and even international levels for more–natural water releases from the dams. Living with Dams Of course, prescribed flooding is not a panacea for the problems of the lower Zambezi basin. Efforts to re–establish natural flood cycles will not necessarily result in the re–establishment of historic floodplain conditions. The health of river systems depends on many other factors as well, including sediment loading, nutrient flows, and the activities of the system’s plants and animals.

Riverine sediments, for example, "play a pivotal role in the ecological functioning and productivity of the river, its wetlands, the delta, and the coastal zone, and hence, greatly influence economic activities in the valley and the adjacent coastal zone," notes Davies. But Kariba and Cahora Bassa reservoirs trap most of the sediment load of the upper and middle Zambezi basins, releasing silt–free waters downstream. Artificial flood releases may increase sediment transport, but they cannot recreate the basin–wide process of sedimentation that once fertilized and aggraded the lower Zambezi. With widespread coastal erosion and mangrove die–back already in evidence, the long–term social and ecological consequences of reduced sedimentation are sobering. Equally problematic are the changes that have taken place in land use and settlement patterns along the lower Zambezi system. Widespread settlement is occurring in historically flood–prone areas of the riverway, as villagers abandon their upland homes and adjust their livelihoods to the regulated Zambezi. To realize the anticipated benefits of restored flood cycles, temporary movement away from flood–prone areas will be required during peak flood releases.

This in turn will require an appropriate flood warning system and a community–based rural development program to make best use of the flood releases. However, after 25 years of mismanagement of Cahora Bassa Dam, attitudes toward floods in the delta are very negative, and these will be difficult to overcome. Although some village elders recall the importance of the historic floods for their livelihood, most young people think that floods are "created by the government" and do nothing but harm. They point to the unanticipated flash flood releases from Cahora Bassa, which crested much more quickly than natural floods and created hardships that slowly rising and receding floodwaters did not. Overcoming such perceptions will require extensive community outreach. According to IUCN Zambezi Basin project manager Baldeu Chande, "one of the great challenges for conservation work in the Zambezi Delta is to work with people and educate them about the values of floods ... but first, we must learn from them." Prescribed releases are expected to produce only moderate floods. These moderate floods are likely to prove beneficial for many floodplain processes.

However, large floods – characteristic of the historic Zambezi system – may be required to remove upland trees that have become established in the floodplain in the absence of flooding, and to flush accumulated organic matter and nutrients from peripheral swamps to the floodplain. As yet, little research has been conducted on species–, community–, or ecosystem–level responses to varied flood releases in the lower Zambezi or elsewhere in sub–Saharan Africa. Building Consensus The process to re–operate the Cahora Bassa Dam in a more beneficial way is gaining momentum and political will, despite the many obstacles and competing considerations. Most notably, a workshop on the sustainable use of the Cahora Bassa Dam was held in October 1997 under the auspices of the Mozambique’s Zambezi Valley Development Authority (GPZ) and Arquivo do Patrimonio Cultural (ARPAC), the main government body doing social research. The workshop drew more than 50 scientists, managers, and decision–makers from Mozambique, southern Africa and beyond.

Participants discussed how the Cahora Bassa Dam might be managed to optimize use of Zambezi water for local development and conservation in addition to other national interests, and discussed immediate actions that could be taken to improve water management and build consensus among Zambezi users. Participants, including three cabinet–level Mozambican officials, concluded that the Cahora Bassa Dam’s outflow should be managed to simulate the Zambezi River’s natural variability in water flow. Future meetings will engage a widening circle of stakeholders and decision–makers in reaching consensus on an integrated management plan for Cahora Bassa Dam and the Zambezi Valley. This circle will include key international stakeholders concerned with hydropower sales from the dam, especially neighboring Zimbabwe and South Africa. Calls to allocate the Zambezi’s waters to benefit river basin communities and ecosystems, in addition to other national and international development interests, are now being received favorably in the decentralized political system of Mozambique. The restoration of the lower Zambezi system is ultimately an exercise in adaptive management. Many conclusions and judgments will be made by observing short–term responses to flood releases and adjusting our prescriptions accordingly.

Decision–makers and river basin managers alike will need to understand the uncertainties that we inevitably face in trying to ameliorate the impacts of large dams. Implementation of a prescribed flooding program at the scale of the lower Zambezi basin is a long–term process. It will demand strong political will, constant community outreach, and continuing international scientific cooperation. The alternative – the continued degradation and decline of the lower Zambezi – would ultimately prove infinitely more costly to the people and wildlife of Mozambique. The author is a wetland hydrologist and the Africa Program Coordinator for the International Crane Foundation in Baraboo, Wisconsin. Cahora Bassa in Chigongo - Tourist attractions @ Travel Advisor! Vkontakte User @ Unknown source The system includes two converter stations, one at Songo in Mozambique and the other at Apollo in South Africa. There are two parallel lines between these two stations, covering 1,400 km, of which 900 km is in Mozambican territory. These HVDC lines work at 533 kV and in Mozambique territory only have about 4,200 towers.

History Portuguese period The Cahora Bassa System started in the late 1960s as a project of the Portuguese in the Overseas Province of Mozambique. South Africa n Governments were also involved in an agreement stating that Portugal would build and operate a hydroelectric generating station at Cahora Bassa together with the high-voltage direct current (HVDC) transmission system required to bring electricity to the border of South Africa. South Africa, on the other hand, undertook to build and operate the Apollo converter station and part of the transmission system required to bring the electricity from the South African/Mozambican border to the Apollo converter station near Midrand . South Africa was then obliged to buy electricity that Portugal was obliged to supply. During its construction, the dam site was repeatedly attacked without success by Frelimo guerrilla insurgents in an attempt to sabotage the project. Portugal increased popular support in Mozambique with this and other development works (see Mozambican War of Independence). The dam began to fill in December 1974.

Until 2007 the dam was operated by Hidroeléctrica de Cahora Bassa and jointly owned by Mozambique, with an 18% equity stake, and Portugal , which held the remaining 82% equity. On November 27 2007 Mozambique assumed control of the dam from Portugal. [1] In 2007, Portugal sold to Mozambique most of its 82 percent stake in the Cahora Bassa hydroelectric power facility in the Southeast African country. Finance Minister Fernando Teixeira dos Santos said Portugal would collect US$950 million (€750 million) from the sale of its part of southern Africa's largest hydropower project. Portugal keeps a 15 percent stake in Cahora Bassa, though it planned to sell off another 10 percent at a later stage to an investor that would be proposed by the Mozambican government. Portugal's Prime Minister José Sócrates signed the agreement with the Mozambican government, during an official visit to Maputo . The agreement ended decades of dispute between Portugal and its former territory in East Africa over the company, called Hidroelectrica Cahora Bassa.

The central disagreement was over the handling of the company's estimated US$2.2 billion (€1.7 billion) debts to Portugal. Mozambican authorities argued they had not guaranteed the debt and therefore should not be liable for the payments. Vkontakte User @ Unknown source Independent Mozambique Mozambique became independent from Portugal in 1975. Since closure, the Zambezi, which is the fourth largest floodplain river in Africa, has received a far more regulated flow rate, but disastrous natural floods still occur. The 1978 flood caused 45 deaths, 100,000 people to be displaced and $62 million worth of damage. According to engineering consultants, "This was the first flood since completion of Cahora Bassa, and destroyed the widely held belief that the dam would finally bring flooding under full control". [2] For further details of ecological problems caused by the dam, see the article on the Zambezi River.

During the Mozambican Civil War (1977-1992) the transmission lines were sabotaged to the extent that 1,895 towers needed to be replaced and 2,311 refurbished over a distance of 893 km on the Mozambican side of the line. In the 1990s, after the end of the civil war, Hidroelectrica De Cahora Bassa (HCB) appointed South Africa's Trans-Africa Projects (TAP) to perform the construction management, quality assurance and design support service for the rehabilitation of the project. TAP assisted HCB in awarding the construction contract to a joint venture company comprising of Consorzio Italia 2000 and Enel, and a scheduled period of 24 months was set for the project. The lines in South Africa were damaged to a minor extent and only normal maintenance was required by Eskom to get these lines back in operation. Work on the project started in August 1995.

The line route in Mozambique passes through dense bush and difficult terrain from Songo to the South African border near Pafuri, with both servitudes infested with landmines from the Mozambican Civil War (1977-1992) that needed to be cleared before construction work could commence. Heavy, unseasonable rainfalls later affected the programme to such an extent that the first line could only be completed in August 1997 and the second in November that same year. During the refurbishment period, TAP developed and implemented various designs and construction methods to improve the overall programme schedules and project costs. In spite of the extreme conditions within which they had to refurbish and reconstruct these lines, the work was completed within schedule and with a limited budget. The lines have, since completion, been subject to numerous tests and energised to its full potential. About 1,100 people were employed during the peak periods of construction.

Vkontakte User @ Unknown source The rainfalls and severe flooding during February 2000 in the Limpopo River valley again caused considerable damage to both lines to the extent that about 10 towers collapsed and need to be reconstructed within the shortest possible timeframe to restore the power supply to South Africa. TAP was again entrusted by HCB with the engineering, procurement and construction management services. TAP managed to temporarily restore power supply through the one line while a more permanent solution could be carried out on the other line. The reconstructed line is used to carry the full line capacity. TAP had to implement unconventional construction techniques to recover temporary supply. The suspension towers next to the river crossing posed a significant challenge for a temporary power solution to obtain the required clearances of the 711 metre level terrain span. Related economic activities Most of the electricity generated by Cahora Bassa, which is located on the Zambezi River in western Mozambique, is sold to nearby South Africa. In 2006, Cahora Bassa transmitted about 1,920 megawatts of power, but the infrastructure is capable of higher production levels and the company had plans to almost double its output by 2008.

In 1994 the total installed capacity in Mozambique was 2,400 MW of which 91 % was hydroelectric. A considerable kapenta fishery has developed in the reservoir. The kapenta is assumed to originate from Lake Kariba where it was introduced from Lake Tanganyika . Annual catch of kapenta in the Cahora Bassa dam in 2003 exceeded 10 thousand tons. It is widely believed that there is a breeding colony of Zambezi Shark "trapped" inside the dam. As the Bull Shark is known to travel >100km upstream, this phenomenon does not conflict with existing scientific and biological fact. In particular an ocean-dwelling species, bull sharks are perfectly capable of living in fresh water for their entire lifespan. Local tribes have indeed reported sightings (and attacks) by this isolated community of shark, although these have yet to be substantiated with hard evidence. See also Cahora Bassa (HVDC) for details of the power scheme based on the dam.

References ↑ Mozambique assumes control of Cahora Bassa IOL ↑ Rendel, Palmer, and Tritton Consulting and Designing Engineers: "Review of the hydrological network, and study of the design of a flood warning system for the Zambezi River". Supplementary report. London: Institute of Hydrology, 1980. Quoted in Richard Beilfuss & David dos Santos: Patterns of Hydrological Change in the Zambezi Delta, Mozambique. Working Paper No 2 Program for the Sustainable Management of Cahora Bassa Dam and The Lower Zambezi Valley (2001) General references To The Victoria Falls : The Zambezi River To The Victoria Falls A Natural Wonder The Zambezi River It is thought Zambezi means ‘Great River’ in the language of the Tonga people who inhabit its middle reaches. However the Lozi refer to the river as 'yambezhi' (pronounced 'le-am-by'), meaning 'heart of all', but it is possible the name has common ancestory in both languages.

For many years the river was spelt 'Zambesi', with the now popular spelling of 'Zambezi' becoming only widely used in the latter half of the last century. The Zambezi River is the forth longest river in Africa (after the Nile, Congo, and Niger) and the largest to discharge into the Indian Ocean from the African continent, flowing for about 2,574 kilometres from its source on the Central African Plateau to sea. Rising in Zambia at a height of 1,524 metres above sea level, the Zambezi flows through, or borders, six countries (Zambia, Angola, Namibia, Botswana, Zimbabwe and Mozambique) before discharging into the Indian Ocean. The Zambezi River basin catchment area extends over the territory of eight countries - Zambia, Angola, Namibia, Botswana, Zimbabwe, Malawi, Tanzania and Mozambique - a catchment area of 1,320,000 km2 with a cumulative mean annual flow of approximately 97 km3 - making it the largest river in southern Africa.

By comparison the Zambezi roughly equates to the Nile, but is significantly less than the annual flow of the Congo, which in turn is significantly less than that of the Amazon. The river is generally separated into three sub-sections, representing its different physical and biological characteristics. The coastal section, or Lower Zambezi , stretches 360 miles up as far as the Cahora Bassa gorge, now flooded by the Cahora Bassa Dam. The Middle Zambezi is 600 miles long, in low-lying country, and is divided from the Upper Zambezi regions of the river by the Victoria Falls, 1,000 miles from the coast. Map of the Zambezi River basin (highlighted) within southern African context The wider Zambezi River Basin is home to some forty million people who speak Bantu-lineage local languages with English and Portuguese being the main official languages. The Basin is well endowed with mineral, water and energy resources, natural tourist attractions like the Victoria Falls, as well as a healthy wildlife population.

Major Tributaries of the Zambezi River The Zambezi has a number of important tributaries, which constitute major rivers in their own right, including the Shire River, flowing from the territories of Tanzania, Malawi and Mozambique, the Luangwa, Kafu and Kabompo rivers, lying wholly within Zambia, the Luena, from the territory of Angola and Zambia, and the Cuando (or Kwando), also known as the Chobe, draining from Angola, Namibia and Botswana. The most westerly of these is the Cuando (or Kwando), draining an area from Angola, Namibia and Botswana. Following a south-easterly course as far as the Botswana–Namibia border, it veers sharply northeastwards to link with the Zambezi via the Linyanti-Chobe floodplain. The mid-section of the Cuando is a floodplain, comparable with the Barotse floodplain, and linked to the latter by a broad belt of alluvium termed the Mulonga-Matebele Plain, which is subject to flooding in the wet season. The Kafue is a north bank tributary with headwaters on the Southern Equatorial Divide.

It initially flows in a general southwesterly direction towards the Upper Zambezi, but the course veers sharply eastwards in the vicinity of a broad floodplain known as the Kafue Flats. This tributary links with the Mana Pools Basin of the Middle Zambezi below the deeply incised Kafue Gorge. The Luangwa River flows in a general south-westerly direction over most of its length – an unusual orientation for a major tributary of an east-draining river. The course veers sharply to the south-south-east a little above the confluence with the Zambezi in the upper reaches of the Chicoa Basin. The mid-Zambezi has a number of relatively minor south bank tributaries, which rise on the central Zimbabwe divide. Their upper reaches flow in a general north-westerly direction. A major tributary of the Lower Zambezi is the Shire, which flows southwards from its headwaters in Lake Malawi, in Malawi.

Hydrology of the Zambezi Catchment The hydrology of the Zambezi catchment is determined by the annual variation of summer rainfall, which is influenced by the movement of the Intertropical Convergence Zone. The further south the zone moves, the greater the delivery of rainfall across the catchment. In winter these boundaries move north, resulting in drier conditions across the Zambezi Basin. River hydrology is further influenced by man. Off-take for agricultural, industrial and domestic use only amounts to about 3 percent of the total flow of the river. Use by hydro-electric facilities, due to the evaporation lost from the large surface area of reservoirs such as Kariba and Cabora Bass Dams, amounts to just over 5 percent of flow. Usage by these sectors is however likely offset by the increased runoff caused by deforestation, drainage of wetlands and other changes in landuse. (Studies on Lake Malawi (Price et al 1998) indicates that increased runoff caused by the clearing of natural forests in the Shire catchment has meant the level of Lake Malawi in the early 1990s was 1m higher than it would have been otherwise).

The annual variation in rainfall between dry winters and wet summers produce high flows in February-April and then progressively lower flows up to a November minimum. The annual flooding is however buffered by the natural flood regulatory capacity of the floodplains developed on the major headwater tributaries. The most important of these are the Barotse and Chobe floodplains in the upper Zambezi, the Kafue Flats on the Kafue River and Elephant March on the Shire River [major tributaries of the Zambezi]. Flow has been further affected by the construction of major dams in the Zambezi (Kariba and Cahora Bassa) and on the Kafue (Itezhi tezhi and Kafue Gorge). (Gupta, 2007) The extensive wetland areas along the Zambezi, in particular the Upper Zambezi catchment are important biodiversity hotspots as well as playing a crucial role in regulating floodwaters.

'The densely vegetated floodplains such as the Barotse and Chobe (Upper Zambezi) and the Kafue Flats, with their shallow gradients, form natural sediment traps that greatly reduce the material supplied to the lower reaches of the river system. These floodplains as a consequence form major wetlands that provide important wildlife refuges, particularly for fish, avifauna and water-dependent mammals, including hippopotamus and the lechwe and sitatunga antelopes. Fish migrate into the inundated grasslands of the floodplains during the floods, spawn, and their fry utilize the rich plankton and benthic communities which develop after nutrient release from decomposing organisms drowned by the floodwaters. Readily accessible stretches of the Zambezi and major tributaries, such as the Barotse floodplain, provide a reliable perennial water source, and are thus an important focus for human settlement and agricultural activity (Davies, 1986).

(Gupta, 2007) Zambezi River Profile Damming the Zambezi As well as Kariba and Cahora Bassa Dams on the Zambezi itself, two other major dams, the Itezhi tezhi and Kafue Gorge Dams have been built on the Kafue, a major tributary of the river. There have been marked changes to the ecology and utilization of the Zambezi River system as a result of the construction of several major dams, such as Kariba Dam and Cabora Bassa on the middle Zambezi, and the Itezhi tezhi and Kafue Gorge Dams on the Kafue. These impoundments had a major impact on the economy of the region. Thus, they represent an important source of hydroelectricity for the whole subcontinent, where there is a rapidly rising demand for power. The introduction of the Lake Tanganyika sardine Limnothrissa miodon (colloquially known as ‘kapenta’) into Lake Kariba in 1967 has formed the basis of an important fishing industry.

Against all expectations, this fish survived discharge via the Kariba turbines and sluice gates, as well as a journey of several hundred kilometres to colonise Cahora Bassa, where it now also forms the basis of an important fishing industry (Davies, 1986; Jackson, 2000). The large dams have also become the focus of an important tourist industry. Nevertheless, these economic benefits have come at considerable human and ecological costs. The construction of Lake Kariba led to the displacement of about 50,000 members of the Tonga tribe which had inhabited the area since about 1100 AD, while about 25,000 people were relocated as a result of the construction of Cahora Bassa. These displacements have led to serious community disturbances, major psychological upsets and emotional problems in the attempt to adapt to new terrain and a new way of life, and bitterness and resentment that rankles to this day (Davies, 1986). The dams have also had severe ecological impacts on the major floodplains, as a result of the reduction of the supply of water and sediment.

The resultant contraction of these wetlands impacts particularly on fish, avifauna and water-dependent antelope species, and are only marginally offset by the added wetlands of the lake shallows (Davies, 1986). This is well illustrated by the collapse in numbers of the semi-aquatic Kafue lechwe (Kobus kafuensis), which is endemic to the Kafue flats, following construction of the Itezhi-tezhi Dam. Today, this species is confined to a fragment of the former range, with a decline from an estimated population of 350,000 at the turn of the twentieth century to less that 30,000 today (Cotterill, 2005). It has also been estimated that the closure of Cahora Bassa led to a 70% reduction of the supply of sediment to the lower reaches of the river, and that this could lead to severe erosion of the Zambezi Delta, threatening both agricultural activity and the important Marromeu wilderness area. During the annual floods prior to construction of the dams, the drowned grasslands of the delta were protected from overgrazing, and thus able to regenerate.

The virtual elimination of the natural flooding regime has disturbed this important ecological dynamic. It may also be responsible for the present marked die-off of the coastal mangroves, and the catastrophic decline of the coastal shrimp-fishing industry (Davies, 1986). The latter author notes that a major problem in quantifying the ecological effects of the construction of the major dams was the lack of baseline environmental data prior to their construction. (Gupta, 2007) In addition to these exitsting dams, it is also proposed to build hydro-electric dam facilities at the Batoka Gorge and Devil's Gorge, both above Kariba, and the Mupata Gorge, between Kariba and Cahora Bassa. These sites were first identified in 1973, and have been proposed repeatedly over the years. As of early 2013 Zimbabwe and Zambia were in advanced stages of planning for the construction of the Batoka Gorge Dam, which will flood the Zambezi at a maximum level to within 5 metres of the base outflow for the Victoria Falls Hydro-electric station. The dam is due for completion in 2019.

The other two damns are looking increasingly likely as the region is predicted to suffer a widening energy deficit. For latest on the proposed Batoka Gorge Dam development please visit Victoria Falls Bits and Blogs Batoka Dam News (external site, opens in a new window). A sixth dam, not shown in the above diagram, is in the advanced stages of planning in Mozambique. Located 60 kilometres downstream of Cahora Bassa Dam has been a hot topic in recent years, being listed as possibly the least environmentally friendly dam in Africa. Zambezi River Dams, planned and constructed [Source: Zambezi River Authority] Management of the Kariba and other hydro-electric facilities requires a network of of thirteen hydrological stations where water levels are monitored daily. Flow measurements are also carried out at eight stations. Major Towns along the Zambezi Along much of the river's length, the population is sparse, but important towns and cities along its course include Katima Mulilo (Namibia), Mongu, Lukulu, Sesheke and Livingstone (Zambia), Victoria Falls and Kariba (Zimbabwe) and Songo and Tete (Mozambique).

Tete continues to dominate the centre-west part of the region, and is the largest settlement along the length of the Zambezi. Crossing the Zambezi The Zambezi is a major geographic boundary and barrier to land based transport. Historically control of the river by the Lozi and TokaLeya boatmen was strategically important to protecting their kingdoms from Matabele (Ndebele) raids, and access to the Barotse heartlands were strictly controlled through strategic crossing points such as Kazungula. Over its entire course, the Zambezi is spanned by only a few bridges: in the upper Zambezi at Chinyingi by a simple suspension bridge and in the Caprivi the Katima Mulilo bridge; in the middle Zambezi the Victoria Falls bridge and two bridges at Chirundu; and in the lower Zambezi sections the Tete suspension bridge and Dona Anna bridge. There are two major ferry crossings, at Kazungula (between Zambia and Botswana) and Caia (in Mozambique). The Cazombo road bridge in Angola was bombed in the civil war and has not yet been reconstructed.

The Katima Mulilo Bridge carries the TransCaprivi Highway over the Zambezi River between Katima Mulilo, Namibia and Sesheke, Zambia. It is a road bridge, completed in 2004, 900 metres long and with 19 spans. The Victoria Falls Bridge was constructed in 1904/5 as a railway bridge and part of Cecil Rhodes's failed scheme for a trans-continental railway stretching the length of Africa. Its location, so close to the Victoria Falls, was not without controversy at the time. At the time of its construction it was claimed to be the highest bridge over water in the world. The bridge was originally designed only to carry railway traffic, supporting two sets of rails, but in 1929/30 the top deck was reconstructed, with only one set of rails, a road and pedestrian footways. Originally known as the Zambesi Bridge, with the construction of later bridges it became known as the Victoria Falls Bridge. The Otto Beit Bridge is a single-lane bridge built in 1938-9 by the Cleveland Bridge Company, the same builders as the Victoria Falls Bridge.

The Otto Beit Bridge was the first modern suspension bridge outside the United States built with parallel wire cables. It has a span of 382 m (main span 320 m). As it was built two decades before the Kariba Dam, the engineers had to consider the annual Zambezi flood, now tamed by the dam: hence the requirement for a single span (which the second bridge did not need). The second Chirundu Bridge is a two-lane, three-span continuous pre-stressed concrete box girder bridge, 400 meters long and 10.3 meters wide and was built in 2002. It is 90 metres upstream from the Otto Beit Bridge, using the same approaches and border control area. The one-kilometre-long Tete Suspension Bridge, finished in 1973 by the Portuguese and designed by Edgar Cardoso, is a major transportation facility in the region. The Dona Ana Bridge spans the lower Zambezi River in Mozambique, effectively linking the two halves of the country. It was originally constructed as a railway bridge in 1935 to link Malawi and the Moatize coal fields to the port Beira.

At that time, it was the longest railway bridge in Africa, with a length of about 3 km, and was known as the Zambezi Bridge (the old 'Zambesi Bridge' had by now become known as the Victoria Falls Bridge). In the 1980s, during the Mozambican Civil War, it was rendered unusable. In 1995, it was repaired with funds from USAID and converted to a single-lane bridge for vehicle traffic. The Dona Ana Bridge is the longest bridge to cross the Zambezi and currently the last before its mouth in the Indian Ocean. In 2007 construction started on the longest road bridge to span the Zambezi to replace the ferry at Caia, and which will become the last bridge before the mouth of the river. With a planned length of 2376 m and width of 16 m it will be exceeded only by the Dona Ana Bridge, which it is planned will be restored as a railway bridge. Above the Falls, the Kazungula Ferry is a pontoon ferry across the 400-metre-wide section of the Zambezi River between Botswana and Zambia.

It is one of the largest ferries in south-central Africa, having a capacity of 70 tonnes. The service is provided by two motorised pontoons and operates between border posts at Kazungula, Zambia and Kasane, Botswana. It links the Livingstone-Sesheke road (which connects to the Transcaprivi Highway at Katima Mulilo) to the main north-south highway of Botswana and also to the Kasane-Victoria Falls road through Zimbabwe. Plans for a bridge to replace the ferry crossing are in development, with construction planned to begin towards the end of 2012. Zambezi River | river, Africa | Britannica.com Zambezi River Alternative Titles: Zambesi River, Zanbere River Related Topics Kariba Zambezi River, also spelled Zambesi, river draining a large portion of south-central Africa. Together with its tributaries, it forms the fourth largest river basin of the continent. The river flows eastward for about 2,200 miles (3,540 kilometres) from its source on the Central African Plateau to empty into the Indian Ocean .

With its tributaries, it drains an area of more than 500,000 square miles (1,300,000 square kilometres). The Zambezi (meaning “Great River” in the language of the Tonga people) includes along its course the Victoria Falls , one of the world’s greatest natural wonders, and the Kariba and Cahora Bassa dams, two of Africa’s largest hydroelectric projects. The river either crosses or forms the boundaries of six countries—Angola, Zambia, Namibia , Botswana , Zimbabwe , and Mozambique —and the use of its waters has been the subject of a series of international agreements. The Zambezi River basin and its drainage network. Encyclopædia Britannica, Inc. Victoria Falls on the Zambezi River as seen from Zambia. G. Holton/Photo Researchers The Zambezi River at sunset.

Art Wolfe—Stone/Getty Images Physical features Physiography The Zambezi rises out of a marshy bog near Kalene Hill, Zambia , about 4,800 feet (1,460 metres) above sea level , and flows some 20 miles before entering Angola , through which it runs for more than 175 miles. In this first section of its course, the river is met by more than a dozen tributaries of varying sizes. Shortly after reentering Zambia, the river flows over the Chavuma Falls and enters a broad region of hummocky, sand-covered floodplains, the largest of which is the Barotse, or Zambezi, Plain. The region is inundated during the summer floods, when it receives fertile alluvial soils. The main tributaries intersecting the river along the plains are the Kabompo River from the east and the larger Lungué-Bungo (Lungwebungo) River from the west.

Similar Topics Kagera River The Zambezi then enters a stretch of rapids that extends from Ngonye (Sioma) Falls south to the Katima Mulilo Rapids, after which for about 80 miles it forms the border between Zambia to the north and the eastern Caprivi Strip—an extension of Namibia—to the south. In this stretch the river meanders through the broad grasslands of the Sesheke Plain until it is joined by the Cuando ( Kwando ) River. Near Kazungula, Zambia, the river, after flowing past Botswana territory to the south, turns almost due east and forms the frontier between Zambia and Zimbabwe. From the Cuando confluence to the Victoria Falls , the Zambezi varies considerably in width, from open reaches with sand islands to stretches of rapids through narrow channels separated by numerous rock islands. The Victoria Falls mark the end of the upper course of the Zambezi, as its waters tumble with a thunderous roar and an enormous cloud of spray. The area around the falls was once covered by a thick layer of lava, which as it cooled formed wide cracks, or joints, that became filled with softer sediments.

As the Zambezi cut its present valley it encountered one of these joints, eroded the sediment, and created a trench, eventually forcing a gap at the lower end of the trench that quickly widened into a gorge. The force of the water also created a second gap at the upper end of the trench that gradually diverted the river until the trench itself was left dry. As the river cut backward it repeated the process, scouring eight successive waterfalls in the past half million years. The Zambezi’s middle course extends about 600 miles from Victoria Falls to the eastern end of Lake Cahora Bassa in Mozambique. It continues to form the boundary between Zambia and Zimbabwe until it crosses the Mozambique border at Luangwa. Below the falls a gorge some 60 miles long has been formed by the trench-scouring process, through which the river descends in a series of rapids. Just upstream of Lake Kariba the river valley widens and is contained by escarpments nearly 2,000 feet high. The middle Zambezi is notable for the two man-made lakes, Kariba and Cahora Bassa (see below), that constitute much of this stretch of the river.

Between the two lakes the Zambezi trends northeast for nearly 40 miles before it turns east below the confluence with the Kafue River , the Zambezi’s largest tributary. In this section the river rushes through two rocky, narrow gorges, the first just below the Kariba Dam and the other above the confluence with the Luangwa River . Britannica Stories Obama Acts to Protect the Arctic At the dam at the eastern end of Lake Cahora Bassa, the Zambezi begins its lower course, during which it descends from the Central African Plateau to the coastal plain . At first the hilly country is replaced by flat areas at the head of the Tete Basin, and the river becomes more placid. About 40 miles downstream the river has cut the Lupata Gorge through a range of hills, where it emerges onto the Mozambique Plain and occupies a broad valley that spreads out in places to a width of three to five miles. Near Vila Fontes the river receives its last great tributary, the Shire River , which drains Lake Nyasa (Malaŵi) some 210 miles to the north. Africa at Random: Fact or Fiction?

At its mouth the Zambezi splits into a wide, flat, and marshy delta obstructed by sandbars. There are two main channels, each again divided into two. The wider, eastern channel splits into the Muselo River to the north and the main mouth of the Zambezi to the south. The western channel forms both the Inhamissengo River and the smaller Melambe River. North of the main delta the Chinde River separates from the Zambezi’s main stream to form a navigable channel leading to a shallow harbour. Hydrology The Zambezi, according to measurements taken at Maramba (formerly Livingstone), Zambia, experiences its maximum flow in March or April. In October or November the discharge diminishes to less than 10 percent of the maximum. The annual average flow reaches about 247,000 cubic feet (7,000 cubic metres) per second. Measurements taken at Kariba Dam reflect the same seasonal pattern; the highest flood recorded there was in March 1958, when the flow reached 565,000 cubic feet per second. Climate Facebook Twitter YouTube Instagram Pinterest The Zambezi River lies within the tropics.

The upper and middle course of the river is on an upland plateau, and temperatures, modified by altitude, are relatively mild, generally between 64° and 86° F (18° and 30° C). The winter months (May to July) are cool and dry, with temperatures averaging 68° F (20° C). Between August and October there is a considerable rise in average temperatures, particularly in the river valley itself; just before the rains begin in October temperatures there become excessively hot, often reaching 104° F (40° C). The rainy season lasts from November to April. Rain falls in short, intense thundershowers—the rate sometimes reaching 6 inches (150 millimetres) per hour—with skies clearing between downpours. In these months the upper Zambezi receives nearly all its total rainfall, and this accounts for the great variation in the flow of the river throughout the year. In all, the upper and middle Zambezi valley receives 22 to 30 inches of rain per year.

Studies have suggested that a microclimate in the area of Lake Kariba has created a rise in precipitation, possibly as a result of a lake breeze blocked by the escarpment that produces thunderstorms. In the lower course of the river in Mozambique the influence of the summer monsoon increases the levels of precipitation and humidity. Temperatures are also higher—determined more by the latitude and less by altitude—as the river descends from the plateau. Plant life The vegetation along the upper and middle course of the Zambezi is predominantly savanna , with deciduous trees, grass, and open woodland. Mopane woodland (Colophospermum mopane) is predominant on the alluvial flats of the low-lying river valleys and is highly susceptible to fire. Grass, when present, is typically short and sparse. Forestland with species of the genus Baikiaea, found extensively on sandy interfluves between drainage channels, is economically the most important vegetation type in Zambia, for it is the source of the valuable Rhodesian teak (Baikiaea plurijuga). Destruction of the Baikiaea forest results in a regression from forest to grassland , a slow process involving intermediate stages of scrub vegetation.

The river additionally has a distinct fringing vegetation, mainly riverine forest including ebony (Diospyros mespiliformis) and small shrubs and ferns (e.g., Haemanthus). In the lower course of the Zambezi, dense bush and evergreen forest, with palm trees and patches of mangrove swamp, is the typical vegetation. Animal life Dams / The Zambezi Basin / Home - HCB Dams Major hydraulic undertakings One of the hydraulic undertakings is the Kariba dam and reservoir, which has a maximum storage capacity of 180 Km3 of water, which makes it the 3rd largest artificial lake in the world and the 2nd largest in Africa. It is located on the stretch of the Middle Zambezi which separates Zimbabwe from Zambia and it is managed by the Zambezi River Authority (ZRA). The other major hydraulic undertaking is the Cahora Bassa dam and reservoir, also on the final stretch of the Middle Zambezi. This reservoir has a maximum capacity of 63 Km3 of water which is the 12th largest reservoir in the world and the 5th largest in Africa.

In order of importance, there follow the Itezhitezi and Kafue Gorge dams, on the Kafue River, Lunsemfwa on the river of the same name, Mulungushi, in Zambia, and Manyame, Masvikadei, Sebakwe and Chivero, in Zimbabwe, which all have storage capacities in excess of 200 million cubic metres. In addition, there are a further 24 large dams, but of lesser capacity, in the Zambezi Basin, 23 of which are in Zimbabwe and 1 in Malawi. Sites for other major hydraulic undertakings have been identified. For some of these, work is at the stage of preliminary or viability studies, or in the Project phase. The diagram shows the main existing undertakings and those envisaged for the main course of the Zambezi River: Batoka, Devil's Gorge and Mupata Gorge, on the Zambia-Zimbabwe international stretch, and M'Panda Uncua, Boroma and Lupata, in Mozambican territory.

These undertakings, together with those that already exist, represent, in the envisaged configurations, a total potential of 12,087 MW, including the Cahora Bassa north bank power station and the potency installed at Victoria Falls. Apart from the large dams mentioned above, there is a substantial series of small dams. Most of these dams, which rarely exceed the capacity of 100000 m3, are intended for agricultural purposes and for public water supply. The great majority of them are in Zimbabwe and Zambia. It is estimated that in Zimbabwe there are about 11,000 small dams, of which 5,820 are located in the Zambezi River Basin. This corresponds to a storage capacity estimated at about 4.6 million cubic metres. In Zambia, although there is no exact knowledge of the number of small dams, it is estimated that their storage capacity amounts to about 12 billion cubic metres, significantly more than in Zimbabwe. They are also located almost exclusively in the Zambezi basin. In Mozambique, apart from Cahora Bassa and the South Bank power station, already built, the construction of the M´Panda Uncua dam is envisaged.

Viability studies and the drafting of projects are under way. But, even during the studies undertaken by MFPZ (Zambezi Promotion and Peopling Mission) and later by the GPZ, a total of 12 sites with hydro-electric and hydro-agricultural potential were identified along the main course of the Zambezi and its main tributaries. These undertakings are envisaged on the Luia River, with a total potency to be installed of around 1,076 MW; at 3 sites on the Revubué River, with a total potency to be installed of around 533 MW, and at Nhamalabué, with a potency to be installed of 1,170 MW. Taken together, these undertakings represent about 9,000 MW, which is less than the hydro-electric potential of the Zambezi basin in Mozambican territory.

Question: On which river is the Cabora Bassa dam situated?
Answer: ZAMBESI RIVER