Hydropower dams threat to freshwater biodiversity

An unprecedented boom in hydropower dam construction underway primarily in developing countries, such as India, could reduce the number of the last remaining large free-flowing rivers by about 20 per cent and pose a serious threat to freshwater biodiversity, scientists say.
The intensified demand for electricity from renewable sources has kick-started the hydropower development into a new era, researchers said.
Following a period of a flattening trend, an unprecedented number of dams for electricity production is currently under construction or planned worldwide.
However, the boom occurs primarily in developing countries and emerging economies in South America, Southeast Asia and Africa, that also hold some of the world's most important sites for freshwater biodiversity, researchers added.

"Hydropower is an integrated part of transitioning to renewable energy and currently the largest contributor of renewable electricity," said Professor Dr Christiane Zarfl (now at Universitat Tubingen) who, together with her colleagues, performed the study at the Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB) in Berlin.
"However, it is vital that hydropower dams do not create a new problem for the biodiversity in the world's freshwater systems, due to fragmentation and the expected changes in the flow and sediment regime.

"That is why we have compiled available data on future expected hydropower dams - to form a key foundation for evaluating where and how to build the dams and how to operate them sustainably," Zarfl said.

Renewables account for 20 per cent of the global electricity production today, with hydropower contributing 80 per cent of the total share.
An expected 3,700 major dams may more than double the total electricity capacity of hydropower to 1,700 GW within the next two decades.
Given that all planned dams are realised, China will remain the global leader in hydropower dam construction although their share of total future global hydropower production will decline from currently 31 to 25 per cent, due to increases in other parts of the world.
The Amazon and La Plata basins in Brazil will have the largest total number of new dams in South America, whereas the Ganges-Brahmaputra basin (mainly India and Nepal) and the Yangtze basin in China will face the highest dam construction in Asia.

"When building new dams, it is important to follow a systematic management approach that considers the ecological, social, and economic consequences of multiple dams within a river basin," said Professor Dr Klement Tockner, head of IGB.
The study was presented at the international congress Global Challenges: Achieving Sustainability hosted by the University of Copenhagen.