Dams + Climate Change = Bad News

Dam Blog Photo.jpg

By Samantha Stahl

The United States has 9,265 dams, second only to China which has a staggering 23,842.[i]  With climate change causing water shortages and storm surges, this might seem like good news. Dams store water, provide renewable energy and prevent floods. Unfortunately, they also worsen the impact of climate change. They release greenhouse gases, destroy carbon sinks in wetlands and oceans, deprive ecosystems of nutrients, destroy habitats, increase sea levels, waste water and displace poor communities.

Crumbling, badly maintained dams also create a flood risk; endangering lives and putting significant financial strain on local governments and industry.

Dams = water loss

Our systematic overuse of fresh water, in addition to the already worsening effects of climate change, creates a need for artificial reserves. According to the American Water Works Association, in 2010 Americans withdrew 355 billion gallons per day (BGD) from the nation’s water systems; 12 percent for public water supply, 32 percent for irrigation and 45 percent for thermoelectric power.[ii]  The average American uses around 2,000 gallons of water per day.[iii] 

Dams would appear to conserve water by storing it, but the bigger picture shows this is not true.

Generally, reservoirs and artificial lakes have a larger surface area than the rivers and channels that feed them. Larger surface areas expose more water to the sun, which speeds up evaporation. And due to the nutrient rich water from trapped sediment, dams and reservoirs also promote aquatic plant growth. The plants’ transpiration contributes to the already heightened evaporation rate.  Every year, about 170 cubic kilometers of water evaporates from the world’s reservoirs. This accounts for roughly 7 percent of all fresh water consumed by human activities![iv]

A study conducted by the European Water Association on the evaporation rate from artificial and municipal lakes and reservoirs in Istanbul concluded that the amount of evaporation per year was equal to the city’s water needs for about 26 days.[v]

The evaporation also affects the microclimates of the surrounding areas, disrupting natural temperature fluctuations, ecosystems and habitats.  For example, increased evaporation in the region of a large dam changes the moisture concentration of the air, leading to increased heavy rainfall.[vi]  This deprives the surrounding areas of their traditional rainfall patterns, placing stress on ecosystems and municipalities that depend on those patterns. And it leads to an increased rate of storm surges, which can create more frequent and intense flooding than the dam was designed to handle. 

Additionally, dams disturb the flow and composition of the water within rivers and channels. Water released downstream from dams has unnaturally high energy and very little sediment, which causes “hungry water” to run forcefully, eroding the riverbeds, without sufficient sediment concentration to slow it down.[vii]  This deepens the riverbed compared to the surrounding water table, which causes the ground water to rush into the channel and become surface water – a process known as incision.[viii] 

Incision is a natural process in the life of rivers and channels, but exacerbated incision, caused by rapid erosion, results in the draining of surrounding groundwater.  The USGS has reported that between 2000 and 2008 the US depleted enough groundwater reserves to contribute 2 percent of the global sea level rise during that time.[ix]

As of 2012, 40 percent of the world’s major river basins’ renewable water supply had been depleted.[x]  This creates a vicious cycle, where growing demand requires more dams to keep up with fresh water usage. Surface and ground water depletion then accelerates too quickly for natural replenishment to be possible. 

Dams = Habitat destruction

Any dramatic change in river composition stresses both up- and downstream habitats. Habitat loss is the leading cause of extinction. 

Dams disrupt fish and bird migration. The change in the composition of the river interferes with the chemical signals guiding species through their biological processes. And the physical barrier of the dam blocks species from their traditional spawning and rearing locations. As a result of this, pollution, and the effects of climate change, fresh water species have lost 76 percent of their populations since 1970.[xi]  The Snake River running through the Northwestern United States, for example, has 15 dams!  Since the completion of the Lower Granite Dam in 1975, the population of Sockeye Salmon in the region has severely declined; between 1985 and 2007, only about 18 Sockeye Salmon return to Idaho each year.[xii]

Additionally, changes in the timing and flow of the rivers can create conditions which threaten the survival of the species that have evolved to live there.  Any alteration in the structure and composition of the river can have disastrous effects on the surrounding species, in many cases leading to extinction.[xiii]       

Downstream ecosystems suffer from the lack of sedimentation in the water that flows over the dam. Normally, nutrient rich sediment regulates and provides nourishment to downstream habitats.  But reduced sedimentation creates less fertile soil, stunting the growth of dependent species.  The lack of vegetative growth can lead to erosion and to the destabilization of the surrounding areas.[xiv] 

Downstream habitats are also severely impacted by changes in salinity and oxygen levels.  Due to the high rate of evaporation and growth of aquatic vegetation within the reservoir itself, water that travels downstream from a dam usually has a higher salinity content and a lower oxygen concentration than normal.[xv]  This change in the chemical makeup of the water creates detrimental conditions for species that previously thrived in those areas.

Dams also negatively impact ecosystems and habitats upstream.  Trapped river borne nutrients can facilitate the growth of toxic algae blooms.  Communities around the world from South Africa to California have had to impose drinking and swimming bans to protect people from water-borne illnesses. Some dams have killed off fisheries and entire aquatic ecosystems.[xvi] 

Even in less devastating circumstances, the new stagnant water environments created in the reservoir damage the conditions of the existing habitat. They also host non-native and invasive species that further undermine the integrity of the surrounding ecosystems.  

Dams = Greenhouse gases

A recent study found that reservoirs account for about 4 percent of human-made climate change.[xvii]

Most reservoirs, especially those in tropical regions, emit significant amounts of greenhouse gases because of anaerobic bacteria that break down the vegetation at the base of the reservoir, giving off carbon dioxide and methane. 

Additionally, the changes to rivers’ timing, chemical and sediment composition, and flow lead to dramatic variations in floodplains and wetlands, which can cause the destruction of surrounding forests.[xviii]  Deforestation contributes significantly to climate change because the trees no longer store additional carbon dioxide and their previously absorbed carbon is released into the atmosphere. And the drying out of wetlands destroys another valuable carbon sink.

Dams are detrimental to carbon sinks in the ocean as well.  Studies of the Congo River reveal that nutrient- and sediment-rich water from the river drives biological processes deep into the Atlantic Ocean, contributing to algae growth.[xix]  When those sediments and nutrients disappear, the conditions that support carbon dioxide-storing algae break down, destroying the carbon sink along with it.  

Additionally, blocking the sediments traveling downstream can have devastating effects when river deltas are deprived of the silt they need to defend against damage from the ocean.  Without the shoring up of river deltas and wetlands, inland ecosystems and human communities become even more vulnerable against the storm surges and sea level rises caused by climate change.[xx] 

Dams = Earthquakes            

Scientists have attributed over 100 earthquakes around the world to dams and reservoirs,[xxi]  a phenomenon known as Reservoir Induced Seismicity.[xxii]  This happens when extra water seeps into the micro-cracks and fissures under the reservoir and surrounding areas and lubricates faults already under tectonic strain.  The 7.9 Sichuan Earthquake in China in 2008, killed 80,000 people and has been linked to the construction of the Zipingpu Dam.[xxiii]    

Dams = Trouble for people already affected by climate change

Dams displace around 80 million people worldwide.[xxiv]  From the people removed from dam building sites to the people who lose their homes to failing dams, most of the displaced communities come from impoverished areas already affected by climate change.

Dams that displace large populations often cause human rights violations. Authoritarian governments in Burma, China, Colombia, Ethiopia, Guatemala, Sudan and other countries have responded to dam opposition with violence, intimidation and threats. In the worst dam-related incident, more than 440 indigenous people died in the suppression of opposition to Guatemala's Chixoy Dam in 1982.[xxv] 

Additionally, old and failing dams generate both dangers and costs. According to the American Society of Civil Engineers, by 2020, 70 percent of the United States’ dams will be more than 50 years old.[xxvi]  And according to ICOLD, 2.2 percent of dams built before 1950 failed before 1995.[xxvii] 

In 2017 nearly 2,000 state-regulated “high hazard” dams need repair. These are dams that could result in a high loss of life if they fail.  While dam construction technology has advanced and dams built today have improved, it would still cost an estimated $300 billion to secure the world’s dams.[xxviii]  And this is in addition to the $2 trillion that has already been spent constructing dams globally since 1950.[xxix] 

Due to the high cost of maintenance and safety, many of the world’s dams get more dangerous as they age. The Mosul dam in Iraq and the Kariba dam in Zambia rank among the world’s most dangerous.[xxx]  Should the Mosul dam fail, it could result in the death of 500,000 people and deprive millions more of power and water.  The 58 year old Kariba dam could result in 3.5 million dead, leave 40 percent of South Africa without power and cause untold damage to surrounding wildlife, plus the destruction of another nearby dam, the Cahora Bassa.[xxxi] 

The US also hosts several dams close to failure. Earlier this year, fear of the collapse of the Oroville Dam Spillway[xxxii]  resulted in the evacuation of 200,000 people in northern California. While the dam is still intact, the eroding spillway, which is a critical piece of California’s flood control network, will make it difficult for the dam to manage heavy flows and rainfall.  And, in February, the Twentyone Mile Dam in Nevada burst, causing massive damage to private property and local infrastructure.[xxxiii] 

Growing recognition that old and eroding dams pose too high a risk have resulted in a growing number of dam removals. The United States has taken down 1,384 dams since 1912, with a majority of those dams removed in the last two decades, and 72 in 2016.[xxxiv]  Removing damaged and aging dams protects the surrounding population from disaster and allows the rivers to restore their natural and biological integrity.         

Rights of Nature = Healthy waterways + Sustainable relationship  

Fresh water is vital to the functioning of Earth’s hydrologic cycle, the maintenance of aquatic and surrounding ecosystems, and the support of human life.  Preserving healthy and high functioning waterways contributes to controlling global temperatures and sustaining fresh water reserves, among countless other benefits. 

Rivers are important in their own right, but also matter for their ability to maintain the health of surrounding river catchments, floodplains, and wetlands.  If we continue to build dams that destroy our waterways’ ability to support vital ecosystems, we continue a historical paradigm that values short-term progress and developmental achievement over the sustainable health and integrity of Earth’s systems.

We will be on the path to a sustainable relationship with a healthier environment when we recognize that Earth has intrinsic rights to thrive, evolve and flourish. Earth law recognizes that Earth’s inherent rights are separate and distinct from property and ownership rights bestowed by humans. By actively promoting this new paradigm, we can forge a more balanced and reciprocal relationship between human activities and Earth’s natural systems. 

Addressing the flaws in the traditional approach to development and acknowledging the rights and interests of waterways will enable us to better care for the planet and its resources. This will benefit humans too.  By understanding sustainable water management and implementing those principles into our industry and governmental systems, we can better address the causes of waterway degradation.  Through understanding what waterways need to function properly, we can create laws and regulations that can better outline the parameters of human activity. 

Protecting waterway health must be one of the highest priorities when determining how water is used.  If it is not, our waterways will continue to degrade and will be unable to provide the basic functions on which both nature and humankind depend. 

To read about the Universal Declaration for Rights of Rivers, click here.

Consider staying informed, volunteering and supporting Earth Law Center’s work to protect our planet’s waterways.


[i] http://www.icold-cigb.net/article/GB/world_register/general_synthesis/number-of-dams-by-country-members

[ii] https://www.awwa.org/Portals/0/files/resources/water%20utility%20management/sotwi/2015-AWWA-State-of-the-Water-Industry-Report.pdf

[iii] http://voices.nationalgeographic.org/2010/08/18/american_lifestyle_costs_nearl/

[iv] https://www.internationalrivers.org/resources/how-dams-affect-water-supply-1727

[v] http://www.ewa-online.eu/tl_files/_media/content/documents_pdf/Publications/E-WAter/documents/40_2006_07.pdf

[vi] http://onlinelibrary.wiley.com/doi/10.1029/2009EO480001/pdf

[vii] https://www.wou.edu/las/physci/taylor/g407/kondolf_97.pdf

[viii] https://definedterm.com/incised_river_channel

[ix] https://pubs.usgs.gov/sir/2013/5079/SIR2013-5079.pdf

[x] https://voices.nationalgeographic.org/2012/03/14/are-we-running-out-of-water/

[xi] https://www.internationalrivers.org/node/8326

[xii] https://www.earthlawcenter.org/new-blog-1/2017/11/dam-removal-to-restore-snake-river-to-health

[xiii]file:///C:/Users/Samantha/Google%20Drive/MY%20JOBS/Earth%20Law%20Center/Blogs/Dam%20Blog/Research/Water_Storage_Paper_21.pdf

[xiv]file:///C:/Users/Samantha/Google%20Drive/MY%20JOBS/Earth%20Law%20Center/Blogs/Dam%20Blog/Research/Water_Storage_Paper_21.pdf

[xv] https://www.internationalrivers.org/environmental-impacts-of-dams

[xvi] https://www.internationalrivers.org/resources/how-dams-affect-water-supply-1727

[xvii] https://link.springer.com/article/10.1007%2Fs11027-007-9086-5

[xviii] https://www.internationalrivers.org/resources/how-dams-affect-water-supply-1727

[xix] https://www.internationalrivers.org/environmental-impacts-of-dams

[xx] http://probeinternational.org/library/wp-content/uploads/2011/10/sedimentation.pdf

[xxi] http://www.sciencedirect.com/science/article/pii/S0012825202000636

[xxii] https://www.internationalrivers.org/sites/default/files/attached-files/ris_final_lorez2.pdf

[xxiii] https://www.internationalrivers.org/sites/default/files/attached-files/ris_final_lorez2.pdf

[xxiv] https://www.internationalrivers.org/sites/default/files/attached-files/world_commission_on_dams_final_report.pdf

[xxv] https://www.internationalrivers.org/campaigns/chixoy-dam

[xxvi] https://www.nytimes.com/interactive/2017/02/23/us/americas-aging-dams-are-in-need-of-repair.html

[xxvii] https://www.internationalrivers.org/and-the-walls-came-tumbling-down

[xxviii] https://www.internationalrivers.org/and-the-walls-came-tumbling-down

[xxix] http://www.hydrocoop.org/the-role-of-dams-in-the-xxi-century/

[xxx] https://oilprice.com/Alternative-Energy/Hydroelectric/The-Worlds-Most-Dangerous-Dams.html

[xxxi] https://oilprice.com/Alternative-Energy/Hydroelectric/The-Worlds-Most-Dangerous-Dams.html

[xxxii] https://www.rt.com/usa/377210-dam-disasters-in-america/

[xxxiii] https://www.nytimes.com/interactive/2017/02/23/us/americas-aging-dams-are-in-need-of-repair.html

[xxxiv] https://s3.amazonaws.com/american-rivers-website/wp-content/uploads/2017/02/15104536/DamsRemoved_1999-2016.pdf