Water

	Report documents dangers of business as usual approach on the Zambezi River
Author	NAWA, DOREEN
Date of paper	03-10-2012
Paper Number	Vol.16 No.232
	ACROSS the continent, African leaders are under pressure to grow their national economies and to raise the standards of living for their people, which translate into increased demands for energy. And for Africa, hydropower is the easiest. Hydropower is being promoted as a source of large-scale energy capacity for the continent. However, southern Africa of which Zambia is a part and home to the Zambezi River is already 60 percent dependent on hydropower for its power supply thereby putting the Zambezi River under pressure. A report released recently presents an evaluation of the hydrological risk of hydro-dependent power system in the face of climate change, using the Zambezi Basin as a case study. According to the report, the future of the Zambezi Basin exemplifies the challenges faced by decision-makers weighing potential benefits of hydropower developments against the risks of hydrological change. The report released titled, "Hydrological Risk and Large Hydropower in Southern Africa", says the result could be uneconomic dams that under-perform in the face of more extreme drought, and more dangerous dams that have not been designed to handle increasingly damaging floods. The report, by Dr Richard Beilfuss, is aimed at assessing risks, uncertainty, and consequences of Zambezi River Basin hydro-dependent power systems. The Zambezi Basin is the largest in southern Africa, with a total drainage area of 1.4 kilometre squares. The report points out that the basin currently has approximately 5, 000 megawatts of installed hydropower generation capacity, including the massive Kariba (whose reservoir is, by volume, the largest in the world) and Cahora Bassa dams. An additional 13, 000 megawatts of hydropower potential has been identified. None of these projects, current or proposed, has seriously incorporated considerations of climate change into project design or operation. The report discusses hydrological variability and uncertainty in the Zambezi Basin, the impact of climate change on basin hydrology and hydropower, and the risks for current and future hydropower developments. The in-depth report warns that new and proposed dams on southern Africa's largest river (Zambezi) are ill-prepared to withstand the shocks of a changing climate. The result could be uneconomic dams that under-perform in the face of more extreme drought, and more dangerous dams that have not been designed to handle increasingly damaging floods. Dr Beilfuss, a noted hydrologist with extensive experience on the Zambezi, evaluated the hydrological risks to hydropower dams in the basin. Overall, Africa's fourth-largest river will experience worse droughts and more extreme floods. According to Dr Beilfuss, dams being proposed and built now will be negatively affected, yet energy planning in the basin is not taking serious steps to address these huge hydrological uncertainties. "Ensuring energy and water security in the Zambezi River basin for the future will require new ways of thinking about river basin development," notes Dr. Beilfuss. "We must avoid investing billions of dollars into projects that could become white elephants." Findings The study found that existing and proposed hydropower dams are not being properly evaluated for the risks from natural hydrological variability (which is extremely high in the Zambezi), much less the risks posed by climate change. The Intergovernmental Panel on Climate Change (IPCC) has categorised 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. Multiple studies by IPCC estimate that rainfall across the basin will decrease by 10-15 percent. The Zambezi runoff is highly sensitive to the 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 of southern Africa's climate is increasingly clear, based on the 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. The report highlights the following risks predicted for the Zambezi Basin over the next century; the basin is expected to experience a significant warming trend of 0.3 to 0.6 degrees Celsius. The increase in temperatures across the basin will result in an increase in open-water evaporation. The report further predicts that all Zambezi Basin countries will experience a significant reduction in the average annual stream flow. It (report) estimates that Zambezi runoff will decrease by 26 to 40 percent by 2050. The report says because large reservoirs evaporate more water than natural rivers, big dams could worsen local water deficits (and reduces water for hydropower). "Already, more than 11 percent of the Zambezi's mean annual flow is lost to evaporation from large hydropower dams' reservoirs. These water losses increase the risk of shortfalls in power generation, and significantly impact downstream ecosystem functions. "The designs for two of the larger dam projects proposed for the Zambezi, Batoka Gorge and Mphanda Nkuwa dams, are based on historical hydrological records and have not been evaluated for the risks associated with reduced mean annual flows and more extreme flood and drought cycles. Under future climate scenarios, these hydropower stations, which are being based on the past century's record of flows, are unlikely to deliver the expected services over their lifetimes," the report read in parts. According to Dr Beilfuss, the Zambezi River is already highly modified by large hydropower dams, which have profoundly altered the hydrological conditions that are most important for downstream livelihoods and preserving biodiversity. "The ecological goods and services provided by the Zambezi, which are key to enabling societies to adapt to climate change, are under grave threat," Dr Beilfuss says. "The region's energy planners and governments must acknowledge these hydrological risks, and take steps to improve planning and management of large dams in the basin," notes Dr Beilfuss. "At minimum, existing and future dams should undergo a thorough analysis of climate risks." And Rudo Sanyanga, Africa programme director for International Rivers, says, "Large-dam hydro poses not just economic risks, but also adaptation risks. Africa has been called the continent 'most at risk' of climate change. Successful adaptation will require new ways of thinking about water resources. We need to act now to protect our rivers as sources of livelihoods and food security." International Rivers is an organisation working to halt destructive river infrastructure projects, address the legacies of existing projects and improve development policies and practices. The report further stresses that understanding rivers is essential to understanding the 21st century's planetary crises and the opportunities for unleashing the regenerative capacities of the Living Earth.