The world’s first great civilizations emerged near rivers such as the Tigris, the Euphrates, the Nile, the Indus and the Yellow River. Rivers have always supported human life, but now their health is suffering because of our dams.
Once a symbol of ingenuity and engineering prowess, the latest research shows that dams destroy river ecosystems and adversely affect human health and well-being. Is further dam development such a good idea after all?
How did dams go from engineering wonder to environmental pariah?
The world has an estimated 800,000 dams, built both for hydroelectric power and to store water. Concerns have mounted over the negative impacts of large dams on both people and the environment. Dams alter a river’s ecosystem from one that’s cold, flowing and connected, to one that’s warm, stagnant and fragmented – with devastating consequences for wildlife. Dams have largely caused freshwater fish numbers to plummet – the world has lost 80 percent of freshwater fish populations since 1970.
Many countries have seen the error of their ways and have started to decommission dams. According to the non-profit American Rivers, over 1,000 dams across the U.S. have been removed to date. Where dams are removed, river ecosystems begin healing right away. On the Elwha River in Washington State, in the very first season after taking down the massive Glines Canyon Dam, over 4,000 Chinook salmon returned to spawn – the first time Chinook have been seen there in more than 100 years. And in New York State, the Saint Regis Mohawk Tribe recently became the first US tribe to remove a federal dam when it took down the Hogansburg dam on the St Regis River, opening up 275 miles of stream habitat to migratory fish.
Internationally, there is a growing movement to oppose destructive dam projects, and the message is getting through. In April 2016, Brazil’s environmental agency, Ibama, suspended the licensing process for the São Luiz do Tapajós dam because of concerns for indigenous peoples. In July 2016, the World Bank suspended financial support for the Inga 3 dam on the Congo River. In the following month, Endesa Chile, Chile’s largest power generator, dropped six hydroelectric projects. The Chinese government has also halted plans to construct a series of dams on one of China’s last free-flowing rivers, the Nujiang. In October, the Peruvian government announced that several dams proposed for the Marañón River, a major tributary of the Amazon, are now off the table during the current administration.
Unfortunately, these are the exceptions rather than the norm. New dams continue to be built and expanded across the world, with relatively few being decommissioned. As one example in the U.S., the United States Army Corps of Engineers has given the green light to build the massive $400 million Chimney Hollow dam and reservoir, which involves diverting huge amounts of water from the Colorado River and pumping it underneath the Rocky Mountains. At the global level, more than 1,400 new dams or water diversion projects are planned or already under construction. In addition to vast ecological harms, many of them are on rivers flowing through multiple nations, fueling the potential for increased water conflict between some countries.
Eight ways dams harm river ecosystems
i. Soil Erosion
Dams hold back the sediment load normally found in a river flow, resulting in the downstream water eroding its channels and banks. This lowers the downstream riverbed and threatens vegetation and river wildlife.
Often cited as a benefit of dams, flooding prevention actually disrupts human and animal systems that have adapted to regular flooding. Annual floods also deposit nutrients and replenish wetlands.
ii. Species Extinction
Changes in temperature and chemical composition, dissolved oxygen levels, and the physical properties of a reservoir are not often suitable for the aquatic plants and animals that have evolved within a given river system. Migratory and breeding activities are among those affected. Indeed, reservoirs often host non-native and invasive species (e.g. snails, algae, predatory fish) that further undermine the river's natural communities of plants and animals.
iii. Spread of Disease
Dam reservoirs can serve as perfect breeding grounds for mosquitoes, snails and flies – the vectors for diseases such as malaria, schistosomiasis and river blindness. Dams have long been associated with elevated burdens of human schistosomiasis, an acute and chronic disease caused by parasitic worms found within snails.
iv. Changes to Earth’s Rotation
NASA geophysicist Dr. Benjamin Fong Chao found evidence that large dams cause changes to the Earth’s rotation, because of the shift of water weight from oceans to reservoirs. Because of the number of dams, Earth’s daily rotation has apparently sped up eight-millionths of a second since the 1950s. Chao said it is the first time human activity has been shown to have a measurable effect on the Earth’s motion.
v. Sedimentation & Siltation
Sediments in water entering a reservoir are deposited at its upper end, forming a delta and steadily raising the level of the upper reaches of the reservoir. This causes flooding due to its bank water effect and shortens the utility of the dam. Silt deposited at the bottom of the reservoir also reduces dam utility. Siltation reduces the water storage capacity of the reservoir and undermines its effectiveness for power generation, irrigation and flood control.
vi. Water logging
Previous rich soils lose their ability to support plant growth when saturated with water, where the water is trapped under the surface but can’t percolate downwards. Dam seepage often causes waterlogging. The Indian Institute of Science estimates that 40 percent of the command area for Sardar Sarovar Dam will become waterlogged.
Irrigation water has higher saline content, leading to salinization of natural systems. Changes in the salt regime can affect the entire ecosystem and disrupt fish breeding. Large riverbank areas are likely to be affected by increased salinity after dam construction.
Dams harm humans too
The world’s dams have allowed cities to sprout in dry lands, but at a steep cost to hundreds of millions of already impoverished people, according to a new report. Lead author Brian Richter, co-director of The Nature Conservancy’s Global Freshwater Program, notes, “Our conservative estimate of 472 million suggests that the number of people [adversely affected by dams] . . . exceeds by six to twelve times the number directly displaced by these structures.”
Those affected include downstream fishermen and farmers. They have their lives and livelihoods altered or even destroyed by dams. Many of them are poor people who may find it hard to adapt. For example, when the Maga Dam and a water diversion scheme went in on Cameroon’s Logone River in 1979, combined hits to floodplain agriculture, fisheries, and other downstream attributes reduced the regional economy by $2.4 million per year, according to the International Union for Conservation of Nature.
Finally, indigenous peoples are particularly hard-hit by destructive dam projects. Many mega-dams are built without the free, prior and informed consent of affected indigenous groups. The flooding from such dams can displace entire communities and inundate their homes, food sources and sacred areas. There have also been many instances of violence directed against protestors of dam projects.
What can I possibly do about a dam?
Until rivers have legal rights that protect them from harmful water projects, we will continue to see dams built for economic gains regardless of environmental impacts. Therefore, Earth Law Center seeks to establish legal rights for all rivers, building off recent victories in New Zealand (Whanganui River), India (Ganges and Yamuna Rivers), and Colombia (Atrato River).
To help achieve this goal, ELC drafted a Universal Declaration of River Rights (“Declaration”), which describes those fundamental rights to which all rivers are entitled. This document is based on existing river rights precedent as well as general principles of river health.
With regard to dams, the Declaration first recognizes the right of all rivers to flow. Additionally, the Declaration calls for governments to “decommission all dams that lack a compelling social and ecological purpose, and that new dam construction shall only occur in exceptional circumstances….” Finally, the Declaration calls for “full free, prior, and informed consent of indigenous and other impacted communities” for any dam projects that do proceed. With these protections implemented in law, we believe that rivers can be restored to health – to the mutual benefit of humans and nature.
Now we need your support to advance the movement to establish legal rights for rivers worldwide! Here is what you can do:
(1) Please sign the Universal Declaration of River Rights and provide feedback, if any, through the online form, available in English and Spanish. You can also visit ELC’s “Rights of Rivers” page for more information.
(2) To start your own river rights initiative, contact email@example.com. You can join the movement to restore the health and beauty of our rivers by preventing new dams from being built, or getting old ones decommissioned.
For more information, email us at firstname.lastname@example.org.
 Freshwater fish are those that spend some or all of their lives in fresh water, such as rivers and lakes, with a salinity of less than 0.05%. https://en.wikipedia.org/wiki/Freshwater_fish
 The command area is the area around the dam, where the benefits of the dam, such as irrigation water, electricity, etc., reach. https://www.proz.com/kudoz/English/agriculture/1308588-command_area.html