Proposed Dams in Southern Africa Ill-prepared for Climate Change
An in-depth study, A Risky Climate for Southern African Hydro, warns that new and proposed dams on Southern Africa’s largest river 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.
Currently, 13,000 megawatts of new large-dam hydro is proposed for the Zambezi and its tributaries. The report finds 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.
Dr. Richard 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. 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.”
The report’s key findings describe a region moving toward the edge of a hydrological precipice:
• The Zambezi basin exhibits the worst potential effects of climate change among 11 major sub-Saharan African river basins, and will experience the most substantial reduction in rainfall and runoff, according to the International Panel on Climate Change. Multiple studies estimate that rainfall across the basin will decrease by 10-15 percent.
• The basin is likely to experience significant warming and higher evaporation rates in the next century. Because large reservoirs evaporate more water than natural rivers, big dams could worsen local water deficits (and reduce 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 occurrence of more frequent extreme floods threatens the stability and safe operation of large dams. Extreme flooding events, a natural feature of the Zambezi River system, have become more costly downstream since the construction of large dams. If dams are “under-designed” for larger floods, the result could be serious safety risks to millions of people living in the basin.
• 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. A recent economic study estimated that the annual total value of river-dependent ecosystem services for one Zambezi floodplain (the Zambezi Delta) ranges between US$930 million and $1.6 billion. The economic value of water for downstream ecosystem services exceeds the value of water for strict hydropower production. These services are not being properly valued in planning for large dams in the basin.
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.”
The report recommends a series of steps to address the coming storm of hydrological changes, including changes to how dams are planned and operated.
“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 Beilfuss. “At minimum, existing and future dams should undergo a thorough analysis of climate risks.”
Visit EcoWatch’s CLIMATE CHANGE page for more related news on this topic.
A tornado tore through a city north of Birmingham, Alabama, Monday night, killing one person and injuring at least 30.
- Tornadoes and Climate Change: What Does the Science Say ... ›
- Tornadoes Hit Unusually Wide Swaths of U.S., Alarming Climate ... ›
- 23 Dead as Tornado Pummels Lee County, AL in Further Sign ... ›
EcoWatch Daily Newsletter
By David Konisky
On his first day in office President Joe Biden started signing executive orders to reverse Trump administration policies. One sweeping directive calls for stronger action to protect public health and the environment and hold polluters accountable, including those who "disproportionately harm communities of color and low-income communities."
Michael S. Regan, President Biden's nominee to lead the U.S. Environmental Protection Agency, grew up near a coal-burning power plant in North Carolina and has pledged to "enact an environmental justice framework that empowers people in all communities." NCDEQ
- Report Urges Biden to Reverse Trump's Environmental Rollbacks ›
- US Environmental Protection Agency (EPA) ›
- Biden's EPA Pick Michael Regan Urged to Address Environmental ... ›
- Biden Faces Pressure to Tackle 'Unfunded' Toxic Waste Sites ... ›
By Katherine Kornei
Clear-cutting a forest is relatively easy—just pick a tree and start chopping. But there are benefits to more sophisticated forest management. One technique—which involves repeatedly harvesting smaller trees every 30 or so years but leaving an upper story of larger trees for longer periods (60, 90, or 120 years)—ensures a steady supply of both firewood and construction timber.
A Pattern in the Rings<p>The <a href="https://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/coppice-standards-0" target="_blank">coppice-with-standards</a> management practice produces a two-story forest, said <a href="https://www.researchgate.net/profile/Bernhard_Muigg" target="_blank">Bernhard Muigg</a>, a dendrochronologist at the University of Freiburg in Germany. "You have an upper story of single trees that are allowed to grow for several understory generations."</p><p>That arrangement imprints a characteristic tree ring pattern in a forest's upper story trees (the "standards"): thick rings indicative of heavy growth, which show up at regular intervals as the surrounding smaller trees are cut down. "The trees are growing faster," said Muigg. "You can really see it with your naked eye."</p><p>Muigg and his collaborators characterized that <a href="https://ltrr.arizona.edu/about/treerings" target="_blank">dendrochronological pattern</a> in 161 oak trees growing in central Germany, one of the few remaining sites in Europe with actively managed coppice-with-standards forests. They found up to nine cycles of heavy growth in the trees, the oldest of which was planted in 1761. The researchers then turned to a historical data set — more than 2,000 oak <a href="https://eos.org/articles/podcast-discovering-europes-history-through-its-timbers" target="_blank" rel="noopener noreferrer">timbers from buildings and archaeological sites</a> in Germany and France dating from between 300 and 2015 — to look for a similar pattern.</p>
A Gap of 500 Years<p>The team found wood with the characteristic coppice-with-standards tree ring pattern dating to as early as the 6th century. That was a surprise, Muigg and his colleagues concluded, because the first mention of this forest management practice in historical documents occurred only roughly 500 years later, in the 13th century.</p><p>It's probable that forest management practices were not well documented prior to the High Middle Ages (1000–1250), the researchers suggested. "Forests are mainly mentioned in the context of royal hunting interests or donations," said Muigg. Dendrochronological studies are particularly important because they can reveal information not captured by a sparse historical record, he added.</p><p>These results were <a href="https://www.nature.com/articles/s41598-020-78933-8" target="_blank">published in December in <em>Scientific Reports</em></a>.</p><p>"It's nice to see the longevity and the history of coppice-with-standards," said <a href="https://www.teagasc.ie/contact/staff-directory/s/ian-short/" target="_blank">Ian Short</a>, a forestry researcher at Teagasc, the Agriculture and Food Development Authority in Ireland, not involved in the research. This technique is valuable because it promotes conservation and habitat biodiversity, Short said. "In the next 10 or 20 years, I think we'll see more coppice-with-standards coming back into production."</p><p>In the future, Muigg and his collaborators hope to analyze a larger sample of historic timbers to trace how the coppice-with-standards practice spread throughout Europe. It will be interesting to understand where this technique originated and how it propagated, said Muigg, and there are plenty of old pieces of wood waiting to be analyzed. "There [are] tons of dendrochronological data."</p><p><em><a href="mailto:firstname.lastname@example.org" target="_blank" rel="noopener noreferrer">Katherine Kornei</a> is a freelance science journalist covering Earth and space science. Her bylines frequently appear in Eos, Science, and The New York Times. Katherine holds a Ph.D. in astronomy from the University of California, Los Angeles.</em></p><p><em>This story originally appeared in <a href="https://eos.org/articles/tree-rings-reveal-how-ancient-forests-were-managed" target="_blank">Eos</a></em> <em>and is republished here as part of Covering Climate Now, a global journalism collaboration strengthening coverage of the climate story.</em></p>
Earth's ice is melting 57 percent faster than in the 1990s and the world has lost more than 28 trillion tons of ice since 1994, research published Monday in The Cryosphere shows.
By Jewel Fraser
Noreen Nunez lives in a middle-class neighborhood that rises up a hillside in Trinidad's Tunapuna-Piarco region.