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Remove Outdated Dams
Over the past 100 years, the United States has led the world in dam building – blocking and harnessing rivers for a variety of purposes, including hydropower, irrigation, flood control, and water storage. The US Army Corps of Engineers has catalogued at least 80,000 dams greater than 6 feet high, along the waterways of the United States – and at least tens of thousands of smaller dams pepper our rivers and streams. Former Secretary of the Interior Bruce Babbitt once observed that, “on average, we have constructed one dam every day since the signing of the Declaration of Independence.”
While dams can benefit society, they also cause considerable harm to rivers. Dams have depleted fisheries, degraded river ecosystems, and diminished recreational opportunities on nearly all of the nation’s rivers. Today, many dams are old, unsafe or no longer serve their intended purposes. For many of these dams where the negative impacts of the dam on the river and riverside biotic communities outweigh the benefits of the dam, then dam removal may be a reasonable approach to restore healthy rivers and riverside communities.
The Damage from Dams
By diverting water for power, dams remove water needed for healthy in-stream ecosystems. Stretches below dams are often completely de-watered.
By preventing the flow of plants and nutrients, dams impede the migration of fish, birds, and other wildlife,
and block recreational use. Fish passage structures can enable a percentage of fish to pass around a dam,
but multiple dams along a river make safe travel unlikely.
Many fish species, such as salmon, depend on steady flows to flush them downriver early in their life and guide them
upstream years later to spawn. Stagnant reservoir pools disorient migrating fish and significantly increase the difficulty
and duration of their migration.
By slowing water flow, most dams increase water temperatures. Yet, other dams decrease temperatures
by releasing cooled water from the reservoir bottom. Fish and other species are sensitive to these temperature
irregularities, which often destroy native populations.
Likewise, when oxygen-deprived water is released from behind the dam, it kills fish downstream.
By withholding and then releasing water to generate power for peak demand periods, dams cause downstream stretches to alternate between no water and powerful surges that erode soil and vegetation, and then either flood or strand wildlife. These irregular releases destroy natural seasonal flow variations that trigger natural growth and reproduction cycles in many species.
Peaking power operations can cause dramatic changes in reservoir water levels — often up to 40 feet — which degrade shorelines and disturb fisheries, waterfowl, and bottom-dwelling organisms. And by slowing flows, dams allow silt to collect on river bottoms and bury fish spawning habitat. Silt trapped above dams accumulates heavy metals and other pollutants. Gravel, logs and other debris are also trapped by dams, eliminating their use downstream as food and habitat.
Following currents downstream, fish can be injured or killed by turbines. When fish are trucked or barged around the dams, they experience increased stress and disease and decreased homing instincts. Warm, murky reservoirs often favor predators of naturally occurring species. In addition, passage through fish ladders or turbines injures or stuns fish, making them easy prey for flying predators like gulls and herons.
Even Broader Environmental Impacts
Dammed rivers have also impacted processes in the broader biosphere. Recent studies on the Congo River have demonstrated that the sediment and nutrient flow from the Congo drives biological processes far into the Atlantic Ocean, including serving as a carbon sink for atmospheric greenhouse gases. Large dams have led to the extinction of many fish and other aquatic species, the disappearance of birds in floodplains, huge losses of forest, wetland and farmland, erosion of coastal deltas, and many other unmitigable impacts.
River systems are the zone of Earth’s highest biological diversity – and also of our most intense human activity. Freshwater biodiversity is in a state of crisis, a consequence of decades of humans exploiting rivers with large dams, water diversions and pollution. Freshwater species are even more endangered than those on land.
Large dams harm biological diversity by flooding land, fragmenting habitat, isolating species, interrupting the exchange of nutrients between ecosystems, and cutting off migration routes. They reduce water and sediment flows to downstream habitat, and change the nature of a river’s estuary, where many of the world’s fish species spawn. The impacts from dams increase the vulnerability of entire ecosystems to other threats, such as climate change.
The irretrievable loss of the Yangtze River baiji dolphin to the Three Gorges Dam, or the elimination of a third of all wild salmon runs on dammed rivers throughout the US West are just the most charismatic examples of how humans are shredding the safety net that supports our own existence and viability. We’re losing life forms that have the ability to nourish us, keep our water clean, produce breathable air and fertile soil, and ultimately make our planet the amazing place it is. If we don’t protect our biological richness and diversity, we undercut the re-generative capacity of the Earth, and we undermine the conditions conducive to life.
Experience From Around the Amazon, Congo, Mekong, and Xingu Rivers
Scientists, led by Professor Kirk Winemiller of Texas A&M, cite the proposed Belo Monte Dam on the Xingu River, a tributary of the Amazon, as a particularly egregious example of environmental destruction. Winemiller warns that about 50 fish species living on the lower Xingu River can be found nowhere else on Earth, and that Belo Monte dam would radically change the river, its ecology, and the lives of local people. Nevertheless, banks, pension funds, investment firms, construction companies, and utilities piled in to own and fund this horrible project. In an effort to preserve the river and the vast wildlife habitat located around it, film director James Cameron produced a 20 minute movie called “Message from Pandora.”
This is not an isolated example. Together the Amazon, Congo, and Mekong rivers hold more than 4,000 fish species – about one third of the world’s freshwater fishes – and most of these species cannot be found anywhere else. The three rivers and their tributaries are currently facing an onslaught of about 450 proposed dams. Many of the proposed dams would be built in particularly sensitive ecological areas, such as the mainstems of the Congo and Mekong, and near waterfalls.
Recent studies published by Science magazine in January 2016, and conducted by scientists from 30 academic, government, and conservation institutions in eight countries, found that dams drastically reduce biodiversity in tropical forests, and cause more than one million additional malaria cases every year in Africa alone. Scientists also found that with average cost overruns of 96%, most hydropower dams don’t make economic sense, and that 85% of them will have to cut power generation due to climate change. The studies conclude that dam builders “often overestimate economic benefits and underestimate far-reaching effects on biodiversity and critically important fisheries.”
Restoring Rivers
Although most rivers cannot be completely restored to historic conditions – simply because of the amount of development that has occurred on and along them – dam removal can often recreate conditions that move the river towards those historic conditions. For example, fish are returning to historic stretches of river that had been previously obstructed on Butte Creek in California and the Clearwater River in Idaho, as a result of dam removals.
Most rivers are dynamic and resilient systems. Some aspects of natural river systems can be restored rapidly after dam removal. For example, spawning fish returned to the Souadabscook River in Maine only months after a dam was removed, and flushing the sediment from the Milwaukee River in Wisconsin following the Woolen Mills Dam removal took only six months.
The Regulatory Environment of Dam Removal and River Restoration
The regulatory environment associated with the removal of dams can be complex. Dams owned by federal agencies are self-regulated. Non-federal dams that produce hydropower are regulated by the Federal Energy Regulatory Commission. Non-federal dams that do not produce hydropower are regulated by the state in which they reside. Most of the dams removed to date have been owned privately, by local governments, or by public utilities.
State fish and wildlife offices are often involved in the decision-making, particularly when the goals of the project include restoration of habitat for migratory and resident aquatic species. It the dam in question is a hydropower facility, the Federal Energy Regulatory Commission can order a hydropower dam under their jurisdiction to be removed for both environmental and safety reasons. Additional resources that can be used in the dam removal and restoration process include InternationalRivers.org and the Hydropower Reform Coalition.
The World Bank Didn’t Get the Memo
Despite all of these documented adverse impacts of dams upon biological diversity, not all infrastructure finance entities appear to be aware of – or responsive to -- these negative impacts. In fact, in early 2016, the World Bank committed to drastically cutting back funding for coal mining companies, but said that it would now switch its multi-billion dollar funding focus to building dams for hydroelectric power. Apparently managers at the World Bank (and other funding organizations) failed to get the memo regarding the harmful impacts of dams upon biological diversity throughout the animal kingdom.
The dam planning processes used by managers at agencies like the World Bank, the IMF, the Army Corps of Engineers, and the US Department of Agriculture, is deeply flawed. Most of the time, planners and engineers are aware of only a fraction of the species a watershed holds before damming proceeds. The environmental assessment process used in these studies needs to be upgraded exponentially.
According to the organization, International Rivers, governments and financiers should systematically compare the costs and benefits of hydropower with wind and solar projects, so that destructive dam building can be avoided in the first place. Taken together, the scientific evidence shows that dams are not the clean, green or cheap source of electric power they are often made out to be. Per International Rivers, “When will the governments and financiers that promote these projects take note?”
Action Plan for Your Area
The enormous impact of dams on biodiversity can be slowed and, to some extent, reversed. First, dams proposed for environmental hotspots of biodiversity should be stopped, and these rivers should be permanently protected. Rivers rich with migratory species are especially inappropriate for dams and should be deemed off limits. The planet’s most lethal dams should be decommissioned.
If there is a dam in your region which is no longer supplying hydroelectric power and which is harming the ecosystem, biodiversity, bird habitat, and the fish spawning process, contact Rivers International and the Hydropower Reform Coalition to find out what actions to take to have the dam taken down.