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Review article - Peer-reviewed, 2021

Navigating trade-offs between dams and river conservation

Thieme, M. L.; Tickner, D.; Grill, G.; Carvallo, J. P.; Goichot, M.; Hartmann, J.; Higgins, J.; Lehner, B.; Mulligan, M.; Nilsson, C.; Tockner, K.; Zarfl, C.; Opperman, J.


Non-technical summary There has been a long history of conflicts, studies, and debate over how to both protect rivers and develop them sustainably. With a pause in new developments caused by the global pandemic, anticipated further implementation of the Paris Agreement and high-level global climate and biodiversity meetings in 2021, now is an opportune moment to consider the current trajectory of development and policy options for reconciling dams with freshwater system health. Technical summary We calculate potential loss of free-flowing rivers (FFRs) if proposed hydropower projects are built globally. Over 260,000 km of rivers, including Amazon, Congo, Irrawaddy, and Salween mainstem rivers, would lose free-flowing status if all dams were built. We propose a set of tested and proven solutions to navigate trade-offs associated with river conservation and dam development. These solution pathways are framed within the mitigation hierarchy and include (1) avoidance through either formal river protection or through exploration of alternative development options; (2) minimization of impacts through strategic or system-scale planning or re-regulation of downstream flows; (3) restoration of rivers through dam removal; and (4) mitigation of dam impacts through biodiversity offsets that include restoration and protection of FFRs. A series of examples illustrate how avoiding or reducing impacts on rivers is possible - particularly when implemented at a system scale - and can be achieved while maintaining or expanding benefits for climate resilience, water, food, and energy security. Social media summary Policy solutions and development pathways exist to navigate trade-offs to meet climate resilience, water, food, and energy security goals while safeguarding FFRs.


water security; ecology and biodiversity; energy; policies; politics and governance; planning and design

Published in

Global Sustainability
2021, volume: 4, article number: PII S2059479821000156

Authors' information

Thieme, M.
World Wildlife Fund
Tickner, D.
World Wildlife Fund
Grill, G.
McGill University
Carvallo, J.P.
University of California Berkeley
Goichot, M.
WWF Greater Mekong Programme
Hartmann, J
Sustainable Water & Energy LLC
Higgins, J.
Nature Conservancy
Lehner, B.
McGill University
Mulligan, M.
King's College London (KCL)
Nilsson, Christer (Nilsson, Christer)
Swedish University of Agricultural Sciences, Department of Wildlife, Fish and Environmental Studies
Umeå University
Tockner, K.
Goethe University Frankfurt
Zarfl, C.
Eberhard Karls University of Tubingen
Opperman, J. J.
World Wildlife Fund

Sustainable Development Goals

SDG6 Clean water and sanitation
SDG15 Life on land

UKÄ Subject classification

Water Engineering

Publication Identifiers


URI (permanent link to this page)