An unprecedented surge in hydropower dam construction, particularly in emerging economies, will bring significant environmental benefits but experts warn that these dams pose a threat to freshwater biodiversity. Abi Millar finds out more.
Hydropower dam construction is on the rise, according to a new report from the Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB) in Berlin. Over the next decade, we can expect to see a construction boom, with an unprecedented number of dams being built in developing countries. The upshot is clear – more communities than ever will have access to renewable energy, and the global electricity production from hydropower will more than double.
On one hand, this will be an important step towards reducing global reliance on fossil fuels. Following the construction of 3,700 major dams, each with a capacity of more than 1MW, global hydroelectric capacity will soar to 1,700 GW. This represents an increase of 73%.
On the other hand, it is well known that hydropower is not a climate-neutral electricity source. As co-author Dr Christiane Zarfl explains, the implications for the environment are far from unilaterally positive: the dams pose a serious threat to freshwater biodiversity and the number of free-flowing rivers in the world will be slashed by 21%.
“The hydropower dams have many benefits, but also some impact on social and ecological issues,” she says. “Freshwater biodiversity is decreased due to the fragmentation of the river by the hydropower dam – the flow of the water and sediment is changed, so the natural dynamic of the river is totally disrupted.”
Dusting off the data
Along with colleagues, Zarfl compiled a database of all the dams that are planned for future construction. This database was presented in October at the congress Global Challenges: Achieving Sustainability, and will be launched in BioFresh, the platform for global freshwater biodiversity. It is intended to provide a key foundation for decision-making, supporting operators in developing the dams sustainably.
“We looked at all the hydropower dams that are planned or under construction on a global scale,” she says. “For that research we consulted a lot of existing databases and literature, as well as contacting non-governmental and governmental organisations just to get the information on what hydropower dams will be built in the future. We also wanted to explore the spatial distribution globally, and so we collated information on the co-ordinates of each dam.
The report, which appears in the journal Aquatic Sciences: Research across Boundaries, quantifies a trend that had been widely recognised, but had not been defined in concrete terms. While the initial surge in dam construction had recently flattened out, this database shows exactly how and where it is picking up pace, and what this will mean for river fragmentation in the affected regions.
The authors found that the boom is occurring primarily in emerging economies, with South America, Southeast Asia and Africa particularly well represented. The countries in question are experiencing rapid population growth and a concomitant rise in energy demand. Because their technical potential for hydropower production has so far not been fully exploited, they have great scope for future dam construction.
“There is a huge demand in these countries for producing electricity in a renewable way, and hydropower is one of the oldest and most well-established technologies available,” says Zarfl.
Fragmented flow
Unfortunately, many of these areas are also hotspots for freshwater biodiversity. For instance, the Amazon, Mekong and Congo basins – all of which will be strongly affected by future hydropower dams – contain 18% of the global freshwater fish diversity between them.
Within Europe, the Balkan region is both a key freshwater biodiversity region and a hot spot for hydropower development. According to a 2012 report, about three quarters of the region’s threatened fish species are vulnerable to the effects of dam construction.
Even at the best of times, freshwater ecosystems are highly sensitive, with biodiversity declining faster in water than on land. Dam construction serves only to exacerbate the problem, throwing these carefully calibrated habitats out of balance.
This can occur in various ways – through blocking migration routes, changing river flows and habitats, opening the gate to alien species invasion and modifying river flow and temperature. There are also dramatic reductions in sediment transport, which may block fish breeding sites. Further down the line, there will be issues for local communities that rely upon fishing for food.
Zarfl’s report highlights exactly how fragmented rivers will become in the wake of future dam construction. Currently, there are 120 large river systems classed as free-flowing, but this figure is poised to drop to 95. While the impacts on biodiversity will likely be severe, the dams under construction in these river systems will constitute just 8% of planned global hydropower capacity.
The authors suggest that the problem might be rectified by concentrating construction efforts in rivers systems that are already fragmented. For instance, fragmentation impacts in East Africa could be diminished by abandoning dams in the free-flowing Rufiji River, and implementing compensatory capacities in the Nile and Zambezi.
As the report explains: “Given the clustering of new dams in specific areas of the world, this is not a generally feasible strategy but should be considered in some regions.”
Considering the consequences
More broadly, the authors recommend a systematic management approach that considers the ecological, social and economic consequences of each dam’s construction, particularly where multiple dams are being built across a single river basin.
“When assessing the impact of the hydropower dam it is also necessary to really assess the cumulative effects of all hydropower dams on river basins,” says Zarfl. “There are already standards in place for hydropower dam construction and operation but so far these standards have only applied to the single hydropower plant and not so much to the whole system.”
They are currently looking to explore the biodiversity issue in more detail, while collaborating with governmental and non-governmental organisations to promote the development of sustainable hydropower. This is a matter of weighing up the known environmental benefits of hydropower against the possible detriments to ecosystems.
As Zarfl explains: “Regulations are especially important for those developing countries, to ensure not only that they have access to renewable electricity but also the best possible living conditions for the population.”
While the hydropower boom looks set to bring many positives, the negatives should not be ignored. After all, it is only through addressing these pitfalls head on that solutions and best practices can be developed.
As the report concludes: “Despite the renewable nature of hydroelectricity, this technology also comes along with severe social and ecological adverse effects, e.g…. fragmentation of free-flowing rivers, and habitat changes, thus further threatening freshwater biodiversity. This does not necessarily need to be the case.”
Under construction…
Baihetan Dam, China
With an expected capacity of 13,050 MW, the Baihetan Dam on the Jinsha river is slated for completion in 2019. It will feature 18 turbines, each with a generating capacity of 725MW. Once finished, it will be the third largest dam in China and the fourth largest in the world.
Currently, China corners 31% of the world’s total hydropower production, but this is set to drop to 25% as increases occur elsewhere. Along with the Ganges-Brahmaputra basin in India, China’s Yangtze basin will see the highest dam construction in Asia.
Grand Ethiopian Renaissance Dam, Ethiopia
Situated on the Blue Nile River, the Grant Ethiopian Renaissance Dam (also known as Hidase Dam) is 40% complete as of October 2014, and is scheduled for completion in 2018. With a planned capacity of 6,000 MW, it will be largest hydroelectric power plant in Africa.
Unfortunately, its environmental and social impacts are open to question, with little information publicly available.
Belo Monte Dam, Brazil
Due for completion in 2015, the Belo Monte Dam complex sits on the Xingu river. It is expected to generate 11,233 MW, making it the second largest hydroelectric dam complex in Brazil. The project, however, has proved controversial, with critics claiming the dam is neither economically viable nor efficient. What is more, it may have a detrimental effect on the environment and local indigenous communities.
In the years ahead, Brazil will be a flurry of construction activity, with the Amazon and La Plata basins boasting the largest number of new dams in South America.
This article is the cover feature for the February 2015 edition of Future Power Technology
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