Skip to main content
Research article - Peer-reviewed, 2019

Mapping the world's free-flowing rivers

Grill, G.; Lehner, B.; Thieme, M.; Geenen, B.; Tickner, D.; Antonelli, F.; Babu, S.; Borrelli, P.; Cheng, L.; Crochetiere, H.; Macedo, H. Ehalt; Filgueiras, R.; Goichot, M.; Higgins, J.; Hogan, Z.; Lip, B.; McClain, M. E.; Meng, J.; Mulligan, M.; Nilsson, C.;
Show more authors


Free-flowing rivers (FFRs) support diverse, complex and dynamic ecosystems globally, providing important societal and economic services. Infrastructure development threatens the ecosystem processes, biodiversity and services that these rivers support. Here we assess the connectivity status of 12 million kilometres of rivers globally and identify those that remain free-flowing in their entire length. Only 37 per cent of rivers longer than 1,000 kilometres remain free-flowing over their entire length and 23 per cent flow uninterrupted to the ocean. Very long FFRs are largely restricted to remote regions of the Arctic and of the Amazon and Congo basins. In densely populated areas only few very long rivers remain free-flowing, such as the Irrawaddy and Salween. Dams and reservoirs and their up- and downstream propagation of fragmentation and flow regulation are the leading contributors to the loss of river connectivity. By applying a new method to quantify riverine connectivity and map FFRs, we provide a foundation for concerted global and national strategies to maintain or restore them.

Published in

2019, volume: 569, number: 7755, pages: 215-221

Authors' information

Grill, G.
McGill University
Lehner, B.
McGill University
Thieme, M.
World Wildlife Fund
Geenen, B.
Tickner, D.
World Wildlife Fund
Antonelli, F.
WWF Mediterranean
Babu, S.
World Wildlife Fund
Borrelli, P.
University of Basel
Cheng, L.
WWF China
Crochetiere, H.
World Wildlife Fund
Macedo, H. Ehalt
McGill University
Filgueiras, R.
WWF Zambia
Goichot, M.
WWF Greater Mekong Programme
Higgins, J.
Nature Conservancy
Hogan, Z.
University of Nevada Reno
Lip, B.
World Wildlife Fund
McClain, M. E.
Delft University of Technology
Meng, J.
WWF Germany
Mulligan, M.
University of London
Umeå University
Show more authors

Sustainable Development Goals

SDG13 Climate action

UKÄ Subject classification

Oceanography, Hydrology, Water Resources

Publication Identifiers


URI (permanent link to this page)