Large-scale hydroelectric dams on Andean rivers disrupt river connectivity to the Amazon.

Large-scale hydroelectric dams on Andean rivers disrupt river connectivity to the Amazon.

© Pixabay

Andean dams versus Amazonian biodiversity

Updated 26.04.2019

A recent scientific study warns of the multiplication of large-scale hydroelectric dams on the Andean tributaries of the Amazon. These installations break up watercourses and pose a threat to the biodiversity and hydrological regime of the entire basin.

Reconciling conservation of biodiversity with renewable energy development could become a key issue. A team of researchers has just shed light on the matter by studying the environmental impact of the hydroelectric dams built on the Andean tributaries of the Amazon. “These installations pose a threat to one of the world's most prolific and biodiversity-rich habitats, explains Pablo Tedesco, expert in macroecology with IRD and co-author of the paper on the subject recently published in Science Advances1. This research requires the involvement of scientists specialising in hydrology and aquatic ecosystems in determining the sites where these structures are to be established”.

142 dams have already been built on the watercourses flowing from the Andes towards the Amazon. 160 others are at the planning stage and could be implemented in the years to come. “These are large structures, most of which are intended for electric power generation, and their multiplication disrupts the connectivity of hydrologic systems”, points out the researcher.

Installations on Amazon tributaries break up the natural environment.

© IRD/M. Jégu

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River connectivity

River connectivity is the natural linking of rivers to one another. Linked to the continuity of water circulation, it controls numerous natural and human systems. The flow of sediment and organic matter is the source of and prerequisite for the development of downstream natural environments. In the Amazon Basin, Andean rivers carry massive amounts of matter, and the nutrients supplied are responsible, at least in part, for the extraordinary variety of freshwater fish. River connectivity is even essential for the survival of aquatic species from floodplains who migrate into Andean rivers to spawn and are the main source of protein for more than 30 million people in the Amazon Basin. Finally, flow sustainability also defines the downstream formation of rivers and the lateral course of the main river, by controlling their bends and sediment deposits. The disappearance or mitigation of seasonal flood events changes the dynamics of intermittent arms and lakes, which are also very important for the existence of species that have adapted to them.

Fragmentation of watercourses

To understand the impact of the fragmentation of watercourses caused by these hydroelectric installations, scientists compiled international data on the dams built or planned in the region. They worked in collaboration with the governments of Brazil, Peru, Bolivia, Ecuador, Colombia as well as conservation organisations. In doing so, they collected vast amounts of data on dams – usage, power, water storage volume - establishing a foundation which will be helpful in the future to measure the actual effects of these infrastructures.

“Existing dams have broken up the tributary networks of six out of the eight major Amazonian-Andean river systems, states the scientist. Future dams could result in significant loss of river connectivity in the watercourses of five of the main systems - Napo, Marañón, Ucayali, Beni and Mamoré”. While mechanisms aimed at reducing the environmental impact are being developed in the construction of these river installations across the world, their effectiveness has yet to be clearly established.



1. Anderson EP, Jenkins CN, Heilpern S, Maldonado-Ocampo J, Carvajal-Vallejos FM, Encalada AC, Rivadeneira JF, Hidalgo M, Cañas CM, Ortega H, Salcedo N, Maldonado M & Tedesco PA. Fragmentation of Andes-to-Amazon connectivity by hydropower dams. Science Advances, 31 Jan 2018.

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