news analysis advocacy
For more frequent updates, visit the AfricaFocus FaceBook page
tips on searching

Search AfricaFocus and 9 Partner Sites

 

 

Visit the AfricaFocus
Country Pages

Algeria
Angola
Benin
Botswana
Burkina Faso
Burundi
Cameroon
Cape Verde
Central Afr. Rep.
Chad
Comoros
Congo (Brazzaville)
Congo (Kinshasa)
Côte d'Ivoire
Djibouti
Egypt
Equatorial Guinea
Eritrea
Ethiopia
Gabon
Gambia
Ghana
Guinea
Guinea-Bissau
Kenya
Lesotho
Liberia
Libya
Madagascar
Malawi
Mali
Mauritania
Mauritius
Morocco
Mozambique
Namibia
Niger
Nigeria
Rwanda
São Tomé
Senegal
Seychelles
Sierra Leone
Somalia
South Africa
South Sudan
Sudan
Swaziland
Tanzania
Togo
Tunisia
Uganda
Western Sahara
Zambia
Zimbabwe

Get AfricaFocus Bulletin by e-mail! on your Newsreader!

Format for print or mobile


Visit AfricaFocus Bookshop US | UK

Southern Africa: Climate Threat to Zambezi Basin

AfricaFocus Bulletin
Oct 3, 2012 (121003)
(Reposted from sources cited below)

Editor's Note

According to a new study released in September, "There will be a significant reduction in the amount of water flowing through the [Zambezi] river system, affecting all eight countries it passes through. The water that feeds the river is expected to decrease by between 26 percent and 40 percent in another four decades. But when the rains do fall, they will be more intense, triggering more extreme floods." Nevertheless, says the author of the study, planning for existing and new dams does not yet take account of the impact of climate change in reducing power generation and capacity for flood control.

The study, A Risky Trip for Southern African Hydro, was conducted for the NGO, International Rivers by Richard Beilfuss, a hydrologist and environmentalist who teaches at the University of Wisconsin-Madison College of Engineering in the US and the University of Eduardo Mondlane in Mozambique. Beilfuss says the region - and the rest of Africa as well - must reconsider the construction of massive hydropower dams and rethink their use as a flood management tool, especially as floods are expected to worsen with climate change.

This AfricaFocus Bulletin contains a news report on the study and excerpts from the introduction and the executive summary. The full study is available at http://www.internationalrivers.org

For previous AfricaFocus Bulletins on climate and environmental issues, visit http://www.africafocus.org/envexp.php

++++++++++++++++++++++end editor's note+++++++++++++++++

Southern Africa: New Urgency to Rethink Dam Projects

26 September 2012

http://allafrica.com/stories/201209270543.html

UN Integrated Regional Information Networks

http://www.irinnews.org

Johannesburg - The massive hydropower dams built on the Zambezi River, the largest river system in Southern Africa, not only supply power to major economies in the region but also help mitigate annual floods. But as electricity demands grow and rising global temperatures affect rainfall patterns, the dams will be unable to meet energy needs or control floods, warns a new study.

The study, A Risky Trip for Southern African Hydro, was conducted for the NGO, International Rivers by Richard Beilfuss, a hydrologist and environmentalist who teaches at the University of Wisconsin-Madison College of Engineering in the US and the University of Eduardo Mondlane in Mozambique. Beilfuss says the region - and the rest of Africa as well - must reconsider the construction of massive hydropower dams and rethink their use as a flood management tool, especially as floods are expected to worsen with climate change.

"Large dams are being built or proposed, typically without analysis of the risks from hydrological variability that are already a hallmark of African weather patterns, much less the medium- and long-term impacts expected from climate change," Beilfuss noted in the report. "Likewise, ecosystem services are rarely given much weight in the energy-planning process."

Extreme floods expected

The report uses the Zambezi basin as a case study to inform governments planning to establish new hydropower plants.

Assessing climate change impact studies conducted on the Zambezi River Basin, Beilfuss said the Zambezi is expected to experience "drier and more prolonged drought periods". Over the next century, rainfall is expected to decrease by between 10 and 15 percent over the basin, according to several studies cited by the Intergovernmental Panel on Climate Change. There will be a significant reduction in the amount of water flowing through the river system, affecting all eight countries it passes through. The water that feeds the river is expected to decrease by between 26 percent and 40 percent in another four decades, the study observed.

But when the rains do fall, they will be more intense, triggering more extreme floods.

No major dams are currently under construction on the Zambezi, Beilfuss told IRIN, but two large dams have been proposed: Batoka Dam on the Middle Zambezi and Mphanda Nkuwa Dam on the Lower Zambezi. "Batoka is politically and financially complex because it must be a joint project between Zambia and Zimbabwe," Beilfus said. "Mphanda is entirely within Mozambique and is in very advanced stages of preparation with a timeline for construction."

There has been considerable opposition to Mphanda Nkuwa, which environmentalists warn could displace several thousand people. Much of the anxiety over its construction is fuelled by the experience of the Cahora Bassa Dam in Mozambique, which has been widely cited as an environmental catastrophe since its construction in the early 1970s by the former Portuguese colonial government.

"None of these projects, current or proposed, has seriously incorporated considerations of climate change into project design or operation," noted Beilfuss.

Guido Van Langenhove, who heads Namibia's Hydrological Services Department, agreed with the concerns raised by Beilfuss and said, "Our dams cannot handle one-in-a-hundredyear [extreme] flood events. They cannot handle the sheer volume of water that might be involved. We have to even consider how to fortify our existing structures."

Disasters

Recent floods and their impact on the existing dams offer a possible view of future disasters. In 2007, heavy rains over the Zambezi threatened the dam structure, forcing the authorities to open the sluice gates of the Cahora Bassa Dam, affecting up to half a million people [some displaced, but others had crops destroyed etc].

Large dams are being built or proposed, typically without analysis of the risks from hydrological variability that are already a hallmark of African weather patterns, much less the medium- and long-term impacts expected from climate change

In a case study on the floods and cyclones that struck Mozambique that year, the Overseas Development Institute warned that the two biggest dams on the Zambezi, Cahora Bassa and Zambia's Kariba, "do not have the spill-way capacity to cope with the very large floods that occur on the river every five to 10 years. At best, the dam operators can slow down the sudden rise in water levels by phasing the spillage of water over a period of a few days, which gives the people living downstream a little more time to evacuate their homes."

Hydrologists in Southern Africa have been calling for a reconsideration of dam planning for years. In 2001, Bryan Davies, an ecologist and a Zambezi river expert, conducted an assessment of the Cahora Bassa and told IRIN, "one of these days there will be a cyclonic event" that the full dams would be unable to cope with.

Part of the problem is that the Zambezi River Basin in Mozambique is a naturally occurring flood plain. In the past, human habitation patterns took flooding into account. When the waters subsided, people would move in to plant in the rich soils, and shift to higher ground when the floods returned, but since the construction of Cahora Bassa, communities have settled much closer to the river, making them more vulnerable, Davies warned.

Van Langenhove, the Namibian official, said people mistakenly believe that the construction of a dam means they will safe from flooding, and so tend to settle close to dams. "Should an extreme event take place, there would be a huge disaster," he said.

Finding alternatives

Beilfuss suggested using hydropower dams to produce electricity only and not to store flood water. "Many hydropower projects are justified on the basis of providing flood control in addition to energy generation. However, allowing for flood storage means the reservoir must be drawn down to provide flood capture space at the very time that this water is most needed to supply energy".

The vast natural flood plains of the Zambezi should be allowed to flood while ensuring people do not settle in those areas, he said. "This will allow for regeneration of the floodplains systems for wildlife and fisheries and agriculture, and also will reduce the impact of extreme floods - which already occur in the basin as it is - on people and property.

"By removing people from flood-prone areas - in accordance with Mozambique and Zambia law, by the way - it becomes especially important to restore modest annual high flows in the basin so that people can secure their livelihoods from fisheries and agriculture," he told IRIN by email.

Beilfuss also suggested that countries in the region improve existing hydropower capacity rather than investing in new infrastructure. "Adding new or more efficient turbines is almost always much lower-impact than building new dams." Countries should also consider alternative sources of energy generation.

In 2011, the eight countries through which the Zambezi flows set up the Zambezi Watercourse Commission (ZAMCOM) to manage the river. Though still a new body, "ZAMCOM is a very important step forward for the integrated development and water conservation in the Zambezi River Basin," Beifluss said. "In particular, the ZAMCOM structure offers the potential to strategically address river development, including hydropower, on a basin-wide level rather than a country-by-country level."

Americo Jose Ubisse, secretary general of the Mozambique Red Cross, has been involved in flood relief operations in Mozambique for many years. He told IRIN in an email that, in the past, issues related to the "environment, climate change and their future humanitarian consequences were deeply undermined... The added value that is coming with these scientific studies must be taken into consideration. Undermining [scientific studies]... can be a big mistake, not only for the future of economic investment but also for the future of humanitarian sustainability."


A Risky Climate for Southern African Hydro

Assessing Hydrological Risks and Consequences for Zambezi River Basin Dams

By Dr. Richard Beilfuss

Published in September 2012 by International Rivers

http://www.internationalrivers.org

Part 1: Introduction

Climate Change In Africa

In the coming decades, billions of people, particularly those in developing countries, will face shortages of water and food and greater risks to health and life as a result of climate change. ...

Africa is already a continent under pressure from climate stresses and is highly vulnerable to the impacts of climate change. Many areas in Africa are recognized as having climates that are among the most variable in the world on seasonal and decadal time scales. Serious floods and droughts can occur in the same area within months of each other. These events can lead to famine and widespread disruption of socio-economic well-being. An estimated onethird of African people already live in drought-prone areas and 220 million are exposed to drought each year. Many factors contribute to and compound the impacts of current climate variability in Africa. These include poverty, weak institutions, limited infrastructure, lack of technology and information, low levels of primary education and health care, poor access to resources, and armed conflicts. The overexploitation of land and water resources, increases in population, desertification and land degradation pose additional threats (UNDP 2006).

Climate change forecasts for Africa predict that the continent's weather patterns will become more variable, and extreme weather events are expected to be more frequent and severe, with increasing risk to health and life (McMichael et al. 2006).This includes increasing risk of drought and flooding in new areas (Few et al. 2004), and inundation due to sea-level rise in the continent's coastal areas (Nicholls 2004). Within the next 50 years, the number of people facing water stress will increase dramatically (Arnell 2004).

Climate change will be an added stress to already threatened species and ecosystems in Africa, and is likely to trigger species migration and habitat reduction on an unprecedented scale. Up to 50% of Africa's total biodiversity presently is at risk due to land-use conversion for settlement and agriculture, deforestation, pollution, poaching, civil war, population growth, and the introduction of exotic species (Boko et al. 2007). Freshwater ecosystems, especially river systems, have experienced rapid degradation due to the past century of water resources development, and are particularly vulnerable to the added effects of climate change (Palmer et al. 2008; Pittock et al. 2008;Vorosmarty et al. 2010).

Hydropower Development, River Systems, and Climate Change

Across the continent, African leaders face an enormous and growing demand for energy, and the added challenge of establishing sustainable energy systems in the face of climate change. Numerous large dams are being built or proposed to meet Africa's long-term power supply needs. Development planners argue that large hydropower dams are a least-cost, indigenous power supply, and note that less than 10% of the region's hydropower potential has been developed. Hydropower is increasingly promoted as a source of energy with low emissions of greenhouse gases, with a production capacity at a scale necessary to meet pressing energy demands with current technology (Pittock 2010).

However, Sub-Saharan Africa (excluding South Africa) is already 60% dependent on hydropower for its power supply, and many individual countries are much more dependent. Recurring drought is commonly acknowledged as a leading contributor to power shortages in numerous hydro-dependent countries. Drought-induced power shortages come at great economic cost to local economies, and add to the perception that African economies are risky places to do business. Kenya, for example, experienced a 25% reduction in hydropower capacity during the 2000 drought, resulting in an estimated 1.5% reduction in GDP valued at $442 million (Stiftung 2010). Expanding the hydrological hydropower in Africa's energy sector would increase dependence of African power grids on rainfall.

Also at stake (but rarely given much weight in the energyplanning process) is the wealth of ecological services provided by river systems that sustain life on earth. Freshwater ecosystems and species are among the most highly threatened in the world. Hydropower dams block fish migrations, inundate upstream habitats, and displace human communities. Downstream, the modification of water flow regimes caused by dams is one of the primary causes of the degradation of freshwater ecosystems worldwide (Richter et al. 1997). ... Extreme fluctuations in flow resulting from peak-power production also stress fish and aquatic ecosystems. In addition to changes in the flow regime, dams can heavily modify water temperatures and the downstream transport of sediment,further affecting river ecosystems. All of these environmental impacts can have serious implications for downstream plant and animal communities, as well as human communities dependent upon the goods and services provided by properly functioning river ecosystems.

Climate change further exacerbates these challenges. The IPCC technical group on climate change and water (Bates et al. 2008) raised concern that climate change will affect the functional operation of existing water infrastructure, including hydropower, and water management practices. Large hydropower projects are highly vulnerable to future changes in precipitation and streamflow. ...

African energy planning is occurring without the benefit of proper analysis of the risks to large dams' viability from hydrological variability that is already a hallmark of African weather patterns, much less the medium- and longterm impacts posed by climate change. With regard to climate change, two risks are routinely overlooked in energy planning at both the sectoral and project levels. First, historical hydrological patterns (on which hydropower operation and project viability are routinely based) are becoming unreliable for predicting future hydrological patterns. Second, the current course of dam building in Africa is not being evaluated with respect to the impact of dam-induced hydrological changes on the ability of rural populations to adapt to climate change.

How can the risks of hydrological uncertainty on African energy portfolios be assessed and integrated into sectoral and project-level decision-making? What policy changes should governments adopt to address the risks of hydropower dependency in national and regional power sectors, in light of such hydrological uncertainty? This report examines risk and uncertainty related to hydropower development and climate change in Southern Africa, focusing on the Zambezi River Basin as a case study.

The Zambezi River Basin

More than a decade ago, the IPCC (2001) categorized the Zambezi as the river basin exhibiting the "worst" potential effects of climate change among eleven major African basins, due to the resonating effect of increase in temperature and decrease in rainfall on potential evaporation and runoff. ...

The Zambezi River Basin is the largest in Southern Africa, with a total drainage area of approximately 1.4 million km2. The Zambezi mainstem, with a total length of 2,574 km, originates in the Kalene Hills in northwest Zambia at an altitude of 1,500m and flows south and eastwards to the Indian Ocean. The river has three distinct stretches: the Upper Zambezi from its source to Victoria Falls, the Middle Zambezi from Victoria Falls to Cahora Bassa Gorge, and the Lower Zambezi from Cahora Bassa to the Zambezi Delta.

Zambezi waters are critical to sustainable economic growth and poverty reduction in the region. In addition to meeting the basic needs of some 30 million people and sustaining a rich and diverse natural environment, the river plays a central role in the economies of eight riparian countries - Angola, Botswana, Malawi, Mozambique, Namibia,Tanzania, Zambia, and Zimbabwe. The Zambezi provides important environmental goods and services to the region and is essential to regional food security and hydropower production.

Home to a rich biological diversity and some of the densest concentrations of wildlife in the world, the Zambezi River Basin features several of Africa's finest national parks. The Middle Zambezi Valley is a UNESCO Biosphere Reserve. Eight Zambezi Basin floodplains are designated as Wetlands of International Importance under the Ramsar Convention, including the Barotse Plain, Busanga Plains, Kafue Flats, Mana Pools (also a World Heritage Site), Lower Zambezi National Park, Elephant Marsh,and the Zambezi Delta. The Zambezi features the most important concentrations in Africa of endangered wattled cranes, African elephant, African buffalo, and many other species.

The Zambezi River Basin currently has approximately 5,000 MW of installed hydropower generation capacity. Major hydropower dams include Kariba and Cahora Bassa Dams on the mainstem Zambezi River, Itezhi-Tezhi and Kafue Gorge Upper Dam on the Kafue River, and the Kamuzu Barrage that partially regulates Lake Malawi water levels for downstream Shire River hydropower production at Nkula Falls,Tedzani, and Kapichira Stage I hydropower dams. An additional 13,000 MW of hydropower potential has been identified (World Bank 2010). None of the Zambezi hydropower development projects, current or proposed, has seriously incorporated considerations of climate change into project design or operation, despite a history of economically devastating droughts and floods that are predicted to become more commonplace in the future.

Numerous studies have addressed the socioeconomic and ecological impacts of existing hydropower development in the Zambezi River Basin. Hydropower dams have resulted in significant shifts in the timing, magnitude, duration, and frequency of annual flood pulses and low-flow events on the Zambezi (Beilfuss 2002). Deleterious ecological changes associated with this hydrological degradation include downcutting of the Zambezi channel below the adjacent floodplain and reduced floodplain water table, invasion of woody savanna and thicket vegetation into open grassland and wetland, abandonment of former distributary channels, displacement of freshwater grassland species with salttolerant grassland species, degradation of coastal mangroves, and reduction in breeding and feeding grounds for endemic and threatened mammal and waterbird species (Tinley 1975, Rees 1978a&b, Handlos and Williams 1985, Beilfuss et al. 2000, Davies et al. 2001, Bento et al. 2007). Socioeconomic concerns include reductions in freshwater and prawn fisheries, floodplain and riverbank agriculture, floodplain water supply, and wildlife carrying capacity for tourism and trophy hunting (SWECO 1983, Bolton 1986, Sushka and Napica 1986, Anderson et al. 1990, Gammelsr?d 1992, Beilfuss et al. 2002, Tha and Seager 2008). Many of these concerns will be exacerbated by the drier, and more drought- and flood-prone conditions resulting from climate change in the Zambezi Basin.

...


Executive Summary

...

Hydrological Variability and Hydropower in the Zambezi River Basin

An understanding of the hydrological variability in the Zambezi River Basin is fundamental to assessing the risks, uncertainties, and consequences of hydro-dependent power systems.

The Zambezi River Basin has one of the most variable climates of any major river basin in the world, with an extreme range of conditions across the catchment and through time. Average annual rainfall varies from more than 1,600 mm per year in some far northern highland areas to less than 550 mm per year in the water-stressed southern portion of the basin.

Runoff is highly variable across the basin, and from year to year. The entire Zambezi River Basin is highly susceptible to extreme droughts (often multi-year droughts) and floods that occur nearly every decade. Droughts have considerable impact on river flows and hydropower production in the basin. For example, during the severe 1991/92 drought, reduced hydropower generation resulted in an estimated US$102 million reduction in GDP, $36 million reduction in export earnings, and the loss of 3,000 jobs. Extreme floods have resulted in considerable loss of life, social disruptions, and extensive economic damage. Hydropower operators and river basin managers face a chronic challenge of balancing trade-offs between maintaining high reservoir levels for maximum power production and ensuring adequate reservoir storage volume for incoming floods.

The natural variability of Zambezi River flows is highly modified by large dams, particularly Kariba and Cahora Bassa dams on the mainstem, as well as Itezhi-Tezhi and Kafue Gorge Upper dams on the Kafue River tributary. Zambezi hydropower dams have profoundly altered the hydrological conditions that are most important for downstream livelihoods and biodiversity, especially the timing, magnitude, duration, and frequency of seasonal flood pulses. More than 11% of the mean annual flow of the Zambezi evaporates from large reservoirs associated with hydropower dams. These water losses increase the risk of shortfalls in power generation, and significantly impact downstream ecosystem functions.

With the dams in place, overbank flood pulses now occur only during major floods in the basin, and are of inadequate volume and duration to sustain healthy functioning floodplain systems that are of global importance, such as Kafue Flats, Mana Pools, and the Zambezi Delta. High flood pulses, when they occur, are often mistimed - they are generated during emergency flood releases or the late dry season in response to required drawdown releases. Dry season flood-recession, essential for river-dependent agriculture, fisheries, and wildlife, is replaced by constant dry-season flows generated from hydropower turbine outflows. The economic impact of the loss of these and other ecosystem services is an important factor in the overall financial risk of hydropower development, especially in a changing climate.

Climate Risks in the Zambezi Basin

The Intergovernmental Panel on Climate Change (IPCC) has categorized the Zambezi as the river basin exhibiting the "worst" potential effects of climate change among 11 major African basins, due to the resonating effect of increase in temperature and decrease in rainfall. The Zambezi runoff is highly sensitive to variations in climate, as small changes in rainfall produce large changes in runoff. Over the next century, climate change is expected to increase this variability, and the vulnerability of the basin - and its hydropower dams - to these changes.

Under future climate scenarios, a hydropower dam based on the past century's record of flows is unlikely to deliver the expected services over its lifetime.

The future picture for Southern Africa's climate is increasingly clear, based on observed trends over the past century and increasing confidence in the range of climate change scenarios developed. Overall, the Zambezi will experience drier and more prolonged drought periods, and more extreme floods. ...

Hydropower's Climate Risks

These staggering climate change predictions, based on the average (not extreme case) of many climate models, have profound implications for future hydropower in the Zambezi River Basin. Climate change has the potential to affect hydropower operations in at least five important ways:

  • Reduced reservoir inflows, due to decreased basin runoff and more frequent and prolonged drought conditions, will reduce overall power output.
  • Increased extreme flooding events, due to higher rainfall intensity and more frequent cyclones, will increase the risk of worse flood impacts from uncontrolled releases, and risks to dam safety.
  • A delayed onset of the rainy season could result in less predictable power production and more uncertainty and complications in using reservoirs for flood management.
  • Increased surface-water evaporation could reduce power production.
  • Increased sediment load to reservoirs, resulting from higher rainfall intensity and corresponding erosion, will lead to a decrease in reservoir capacity and greater difficulty in managing floods.

Numerous studies have indicated that hydropower economics are sensitive to changes in precipitation and runoff. Most hydropower projects are designed on the basis of recent climate history and the assumption that future hydrological patterns will follow historic patterns. However, this notion that hydrological systems will remain "stationary" in the future (and thereby predictable for the design and operation of hydropower schemes) is no longer valid. Under future climate scenarios,a hydropower station based on the past century's record of flows is unlikely to deliver the expected services over its lifetime. It is likely to be over-designed relative to expected future water balances and droughts, and under-designed relative to extreme inflow events. Extreme flooding events, a natural feature of the Zambezi River system, have become more costly downstream since the construction of large dams, and will be exacerbated by climate change. The financial and social impact of a major dam failure in the Zambezi River Basin would be nothing short of catastrophic. ...

Ecosystem Services Undervalued

The wealth of ecological services provided by river systems that sustain life on earth are rarely given much weight in the energy planning process. The current course of dam building in Africa is not being evaluated with respect to the impact of dam-induced hydrological changes on the ability of rural populations to adapt to new flow regimes,much less on their ability to adapt to climate change's impacts more generally. Ecosystem services are of critical importance for adaptation to climate change. ...

The value of the ecosystem services threatened by hydropower development in the Zambezi River system is astonishing. A recent economic valuation study estimates that the annual total value of river-dependent ecosystem services in the Zambezi Delta is between US$930 million and $1.6 billion. Agriculture, fisheries, livestock, tourism, and domestic water supply are all affected. Cumulatively, the economic value of water for downstream ecosystem services exceeds the value of water for strict hydropower production - even without valuation of biodiversity and cultural uses of the river system.


AfricaFocus Bulletin is an independent electronic publication providing reposted commentary and analysis on African issues, with a particular focus on U.S. and international policies. AfricaFocus Bulletin is edited by William Minter.

AfricaFocus Bulletin can be reached at africafocus@igc.org. Please write to this address to subscribe or unsubscribe to the bulletin, or to suggest material for inclusion. For more information about reposted material, please contact directly the original source mentioned. For a full archive and other resources, see http://www.africafocus.org


Read more on |Africa Economy & Development||Africa Climate Change & Environment|

URL for this file: http://www.africafocus.org/docs12/zam1210.php