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renewable energy > features > africa : the wrong climate for big dams

Africa : the wrong climate for big dams

Posted: 09 Feb 2010

by Lori Pottinger

Some 550 million people in Africa live without electricity and power is critically short in many African countries. But with increasing droughts and climate uncertainty this is not the right time to rush into more big dams when there are so many other promising renewable energy alternatives, says Lori Pottinger

Africa is the least electrified place in the world. leaving nearly half its countries with a power crisis. Solving this huge problem is made more difficult by widespread poverty. And, because most Africans live far from the grid, the cost of bringing electricity to them is high.

Protest against Kajbar dam, Sudan
Nubian activists protest plans to build Kajbar Dam on the Nile, Sudan.

Under these challenging conditions, there are no second chances for electrifying Africa: it must be done right the first time. Yet many of the continent's energy planners are pinning their hopes for African electrification on something as ephemeral as the rain, by pushing for a grid of large hydro dams across the continent. The World Bank has joined the fray, with its latest World Development Report calling for a major hydropower rollout for the continent. And dam-building nations like China and Brazil have descended, on the hunt for lucrative contracts.

The failure of this vision lies in the unpredictable nature of Africa's rivers, a situation that will be made worse by a changing climate. New dams are being built with no examination of how climate change will impact them. Many existing dams are already suffering from drought-caused power shortages.

Climate change is expected to dramatically alter the hydrology of African rivers, creating both worse droughts and more dangerous floods (the latter causing safety concerns for poorly maintained or operated dams). At the same time, many African nations face huge water-security problems. In this climate, the proposed frenzy of African dam building could be literally disastrous.

The Zambezi below Cahora Bassa Dam, Mozambique
The Zambezi below Cahora Bassa Dam, Mozambique. There are plans to build a huge hydro-power station at Mphanda Nkuwa, further down the river.
The failure of this vision lies in the unpredictable nature of Africa's rivers, a situation that will be made worse by a changing climate. New dams are being built with no examination of how climate change will impact them. Many existing dams are already suffering from drought-caused power shortages.

Climate change is expected to dramatically alter the hydrology of African rivers, creating both worse droughts and more dangerous floods (the latter causing safety concerns for poorly maintained or operated dams). At the same time, many African nations face huge water-security problems. In this climate, the proposed frenzy of African dam building could be literally disastrous.

The oft-repeated sound-bite that only 5-8 per cent of the continent's hydro potential has been tapped is an incomplete message at best. The other side of the coin is that Africa is already dangerously hydro-dependent. Meanwhile, Africa has not developed even a tiny fraction of a percent of its available solar, wind, geothermal, or biomass power.

Map of Zambezi dams
Map showing Zambezi dams.

While large dams have done little to bridge the "electricity divide" that has left so many Africans in the dark, renewable energy projects can be scaled to meet the needs of the average village (or, for that matter, urban area). At a time when global warming threatens to make the continent's rivers even less reliable for large hydro projects, and their waters more precious for other uses, donors and governments should be looking to diversify the energy mix.

Risky Rivers

Past hydrological records, upon which dozens of new large dams are being planned, unfortunately have little bearing on future hydrology. The economic impacts of hydro-vulnerability will be felt both in the costs of power cuts upon industrial output, and the cost of wasted investments in non-performing dams.

The economic risks of unviable dams will compound the risk already being taken by so many African nations: that of over-dependency on hydropower to supply electricity. Already, the majority of sub-Saharan states get most of their electricity from rivers. (At least two nations have begun to reverse this dependency: Tanzania, which is now developing its gas fields, and Kenya, which has become an African leader in geothermal power, and is looking to develop wind farms.)

The other climate risk is that many large dams seriously harm downstream riverine communities and ecosystems, which will make climate adaptation that much harder for the many millions of Africans who depend directly on rivers and lakes for their livelihoods, food and water supply. Like the fairy tale that warns of "killing the goose that lays the golden egg", African dam planners are putting at risk irreplaceable "golden egg" resources such as clean water supply, agriculturally important sediments that replenish floodplains, riverine forests and fisheries.

Some dam planners agree that African hydroelectric schemes may be plagued by variable rainfall patterns, but believe that they can "play the odds" and just build more dams, across a wider region, and connect them all with transmission systems that would allow power to be traded to places where drought has crippled the power supply. Yet it's hard to sell electricity from empty reservoirs.

350 protest Africa
In late October 2009, Africans joined a global day of protest to call attention to the need to keep carbon at 350 ppm. Photo credit: 350.org

Climate scientists predict truly alarming changes to various African waterways. UK government researcher Sir Nicholas Stern recently predicted that a 3-6� Celsius increase in temperature in the next few years will result in a 30% to 50% reduction in water availability in Southern Africa. Scientists have discovered evidence that droughts in West Africa lasted centuries in the past. Their 2009 study suggests global warming could create conditions that favour extreme droughts across much of Western Africa, home to Africa's biggest reservoir (Akosombo's Lake Volta), among others.

East Africa has been drying since the mid-1980s, a trend that is already shaving percentage points off GDP for the region's states. A new report, "Large Scale Hydropower, Renewable Energy and Adaptation to Climate Change" by AFREPREN states, "Kenya's GDP is equivalent to US$29.5 billion; the estimated loss during the aforementioned drought-induced power crisis was about 1.45% of GDP. This translates to US$442 million lost which could have been used to install 295 MW of new renewable power capacity."

Most of the Nile Basin states get more than 70 per cent of their electricity from hydro. The Intergovernmental Panel on Climate Change notes that there has already been "a reduction in runoff of 20% between 1972 and 1987" in the Nile, and "significant interruptions in hydropower generation as a result of severe droughts". Even though some parts of Africa are expected to receive more rain, that increase is expected to be overwhelmed by an increase in temperature across the continent, which will lead to higher evaporation rates.

A 2006 study by climate experts at the University of Cape Town revealed that even a small decrease in Africa's rainfall could drastically reduce river flows, affecting a quarter of the continent. For example, a 10% reduction in rain over the Johannesburg area could lead to a 70% drop in the Orange River's levels. In parts of northern Africa, river water levels would drop more than 50%. "It's like erasing large sections of the rivers from the map,'' said Maarten de Wit, who headed up the study.

Energy Insurance

African nations have many better alternatives to large-scale hydro. A few examples:

Geothermal: As the UN notes, Africa has an abundance of geothermal potential. Says Achim Steiner, UN Under-Secretary General and UNEP Executive Director: "There are at least 4,000MW of electricity ready for harvesting along the Rift. It is time to take this technology off the back burner in order to power livelihoods, fuel development and reduce dependence on polluting and unpredictable fossil fuels. From the place where human-kind took its first faltering steps is emerging one of the answers to its continued survival on this planet."

UN figures show that Africa has tapped less than 0.6 per cent of its geothermal. Kenya is the exception, with 10% of its electricity now coming from geothermal.

Solar: Africa's potential is nearly limitless. A new study co-sponsored by Justi�a Ambiental and International Rivers shows that Mozambique's huge and virtually unexploited solar potential is about 1.49 million GWh � thousands of times more than the country's current annual energy demand. And this power is distributed evenly across the country. Exploiting this energy would benefit the more-than-80% of Mozambique's population that is now off-grid.

Wind: Wind potential is also high in many parts of Africa, and is finally beginning to be developed (new large projects are underway in Kenya and Egypt, for example).

Co-gen: The production of electricity from steam, heat, or other energy sources as a by-product of another industrial process is well-suited to many African nations. AFRPREN estimates that Africa could get 20% of its electricity from co-gen. Mauritius now gets almost half of its electricity from co-gen plants using mostly sugar cane waste.

Efficiency: Energy efficiency is critical for all nations but � perhaps surprisingly � even more so for poor nations where energy use is just starting to grow. Setting efficiency standards early can help make every dollar invested in energy supply go that much farther, by reducing the cost of systems needed to power villages and towns, and freeing up existing power supply for other uses. The McKinsey Institute estimates that developing countries could save an estimated $600 billion a year by 2020 by investing $90 billion a year in energy-efficient cars, appliances and production methods.

Diversifying Africa's energy sector would help its climate-adaptation efforts in key ways: it would de-emphasise reliance on erratic rainfall for electricity, reduce conflict over water resources, and protect river-based ecosystems and the many benefits they bring. And it would share the energy wealth with the half-a-billion Africans now living in the dark.

The world's richest, highest-carbon-emitting nations owe it to Africa to help it develop its clean energy resources � projects that will help in climate-change adaptation efforts, rather than hinder them. Healthy rivers are priceless. Let's not let Africa learn that the hard way.

Lori Pottinger is an Editor of World Rivers Review, published by International Rivers. This artcle first appeared in the December 2009 issue of World Rivers Review and is publisheds by arrangement with Third World Features.

How dams affect water supply

Lori Pottinger writes: Most rural Africans are directly dependent on surface water - rivers, wetlands, springs and lakes - for their water supply. Today, 20 African countries experience severe water scarcity and another 12 will be added in the next 25 years. As the climate changes, free-flowing, healthy rivers will become an even-more-valued resource than they are today. Dams are expected to affect water quality and quantity for millions of downstream users. A few ways that dams harm water supply include:

  • By trapping river-borne nutrients, dams can lead to the growth of toxic algaes. Massive algal blooms in reservoirs in the ex-USSR, South Africa and California have rendered reservoirs unfit to drink. Four hydro dams in California have nearly killed off the fisheries of the Klamath River, and made the river unsafe for drinking or swimming. Water stored for months or even years behind a major dam may become lethal to most life in the reservoir and in the river for long distances below the dam. Reservoirs that receive treated effluents from upstream towns and cities are more apt to have this problem.

  • Dams also lead to riverbed deepening for tens or even hundreds of kilometres below the reservoir. Riverbed deepening can lower the groundwater along a river, threatening vegetation and local wells in the floodplain and requiring crop irrigation in places where there was previously no need.

  • Tropical reservoirs are particularly prone to colonisation by aquatic plants. In addition to causing other problems, mats of floating plants can lower reservoir levels. Losses of water from evaporation and transpiration in weed-covered reservoirs can be up to six times higher than those from evaporation in open waters.
Kunene River
A Himba man at the Kunene River, upstream of the Epupa dam site, Namibia.
  • Because they greatly increase the surface area of water exposed to the sun, dams can increase evaporation. About 170 cubic kilometres of water evaporates from the world's reservoirs every year, more than 7% of the total amount of freshwater consumed by all human activities. The annual average of 11.2 cubic kilometres of water evaporated from Nasser Reservoir behind the High Aswan Dam is around 10% its storage, and is roughly equal to the total withdrawals of water for residential and commercial use throughout Africa. The proposed Epupa Dam reservoir would have evaporated more water than the nation's capital city uses in a year.

  • Rising salinity (which ruins the land for farming) is another risk made worse by evaporation from reservoirs and changes to flows downstream. High salt concentrations are poisonous to aquatic organisms and corrode pipes and machinery.

  • Dams change the timing, amount and chemical composition of a river's flow, leading to dramatic changes to groundwater-storing floodplains and wetlands. Such changes can lead to the destruction of forests, which among other things help regulate local climate. Kenya's Tana River floodplain forest appears to be dying out as it loses its ability to regenerate because of the reduction in high floods caused by a series of dams upstream. The Lower Zambezi has lost much of its rich floodplain and wetlands due to upstream dams, with wide-ranging and costly effects throughout the ecosystem.

© People & the Planet 2000 - 2010
Solar panels provide homes with electricity, In Cacimbas, Ceara, Brazil. Photo: Roger Taylor/NREL
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