By: Makenna Christensen

Photo: Lode Lagrainge via Unsplash, Gordon Dam (Australia)

Hydropower accounts for two-thirds of all renewable energy used to produce electricity globally, meaning it is championed above all other renewable resources such as solar, wind, geothermal, and biomass. Hydropower relies on fast-moving water, usually created by discharge volumes from large rivers that spin a generator’s turbine and thus convert the flow of water into electricity. The upside of hydroelectric energy is that it produces high-quality energy, meaning it creates significant useful energy from a given energy resource. There is also still untapped potential for energy growth, as 71% of the Earth’s surface is covered in water, and the ocean’s waves and tides can also be used to generate electricity.

The downside, however, is that redirecting water through damming results in the displacement of people and wildlife, biodiversity loss, and large quantities of methane gas being emitted into the atmosphere. While hydroelectric power in its ideal form is marketed as clean energy, the impacts of dams on the environment pose a significant level of degradation in the long run.

Considering its shortcomings, hydroelectric energy should not be regarded as clean energy, as it causes environmental degradation that is the direct effect of damming two-thirds of all the major rivers on the Earth. Damming and rerouting waterways can cause severe flooding, as new land is inundated by water for reservoirs and new pathways, and natural rivers are drained dry in the process. Flooding new environments results in the unintentional release of methane, a greenhouse gas thirty times more potent than carbon dioxide. This is due to the decomposition of organic material (such as trees and plants) in an oxygen-starved environment, as the bacteria break down dying plants for their carbon needs and release methane as a byproduct.

Similarly, impoundment and pumped storage facilities can cause serious environmental harm to surrounding areas. These alter the amount and quality of water flowing downstream, such as available oxygen levels, which affect plant life as well as aquatic and land-based animal species. Dams similarly reduce sediment and nutrient flow downstream, which creates severe chemical and temperature changes in the water. In doing so, dangerously nutrient-dense bodies of water are formed upstream, which promotes rapid eutrophication, while leaving downstream fish habitats with no nutrients or sediments to help nourish them. Eutrophication is a process that occurs naturally over time in all bodies of water (usually due to run-off or stagnant water), in which excessive nutrient buildup leads to dense algae growth and other plant matter starving the aquatic biota of needed oxygen, resulting in sometimes-massive die-off.

Furthermore, turbines kill fish in the river, and although this impact can be somewhat mitigated through the use of fishways, these structures lack effective architecture, which hampers large numbers of migratory fish. The Chinese paddlefish, one of the world’s largest freshwater species, went extinct in China due to the impacts of damming multiple areas of the Yangtze River. In 2019, National Geographic reported on the World Wildlife Fund’s assessment of river connectivity, claiming their scientists warn, “such fragmentation of the world’s major rivers, caused mainly by dams, threatens the ecosystem services that both people and wildlife depend on for their survival. Free-flowing rivers, they say, provide food for hundreds of millions of people, deliver sediments crucial to agriculture, mitigate the impact of floods and droughts, and underpin a wealth of biodiversity.” Dams also block anadromous fish such as salmon, which live in the ocean but come upriver to spawn, from being able to access historical spawning reaches and migratory routes. The creation of new dams destroys both land and aquatic species’ habitats. Fish habitats are shaped directly by physical factors such as water level, water velocity, shelter opportunities, and access to food. Draining a natural river by diverting water is devastating to fish populations.

Photo: Kate Ross via USACE (Fishways); Fishway on John Day Dam

Three Gorges Dam, China

While protecting the environment for the environment’s sake is of utmost importance, the effects of hydropower on the human population should not be discounted. One of the most notorious sources of hydroelectric power is the Three Gorges Dam on the Yangtze River in China. Proposals to create this dam started back in 1919 due to fears of floodwaters overtaking cities. Concerns about the dam’s negative effects on the surrounding environment, however, delayed start of the dam’s construction until 1994. It is one of many dams that has been built on this river, but the Three Gorges Dam is located farthest downstream.

Since June 2020, the Chinese people have seen extensive flooding and the dam is buckling under the most extreme water flows of this year’s rainy season. However, even with this year’s extensive rainfall, sources such as a Chinese hydraulic engineering expert report that these worries about the structural soundness of the Three Gorges Dam are misplaced. The dam was created not only to harness the power of water, but also to prevent catastrophic floods from impacting the lower reaches of the Yangtze. The rigidity and sustainability of the dam is a highly debated topic among scientists.

In redirecting the natural flow of the river, the dam had also flooded nearby cities. Upon initial construction of the Three Gorges Dam, the project set a record for the number of people it displaced, wiping out entire historic cities, towns, and villages, all while leaving more than 1.3 million (though some critics suggest closer to 1.9) without homes. The city of Kaixian, home to over 1,300 archaeological sites, was the last town to be flooded for the reservoir. The project also wiped out the history and relics of the ancient Ba people who lived in the region around 4,000 years ago.

Three Gorges is the world’s largest hydropower project and is notorious for being plagued by corruption and inflated costs, provoking environmental degradation, and human rights violations, including resettlement issues engendered by forced displacement. While the governing body has compensated the population for its displacement, there is widespread local corruption and lack of funding to support such a mass migration of people.

In January 2019, the study, Long-term Prediction of Greenhouse Gas Risk to the Chinese Hydropower Reservoirs was published evaluating the current and long-term risks of Chinese hydropower reservoirs with a model known as the Greenhouse Gas Risk Assessment Tool (GRAT). The model predicted that until 2018, the twelve reservoirs studied fell under medium risk, which risk was projected to slowly decrease over 100 years. However, that is not the case for the Three Gorges Dam, which is experiencing high levels of methane and carbon dioxide emissions.

Among the worst of the environmental impacts is the degradation in the cliff regions of the Yangtze River, resulting in landslides and flooding of non-residential areas, which has caused an increase in waterborne diseases. Similarly, the dam rests on two geological fault lines, the Jiuwanxi and the Zigui-Badong. It is feared that rapid changes in water pressure during rainy seasons could trigger reservoir-induced seismicity, further adding to the issues of landslides and soil erosion in the area.

Some argue that when comparing hydropower to fossil fuels, we are better off with this supposedly “clean energy.” However, the environmental degradation caused by building hydropower facilities is quickly amounting to the levels of destruction caused by coal mining and oil drilling. While the Three Gorges Dam and others like it create more power than coal plants, the environmental impacts are just as severe. Therefore, while neither is sustainable, nor do they compensate for the real costs of their environmental impacts, hydroelectric power may be the lesser of the two evils for now.

Dams will continue to displace people and have already done so to tens of millions worldwide. Hydroelectric power is not a sustainably sourced energy, but rather the practice of state-funded greenwashing at its finest. Politics play a huge role in the world of energy. Here in the United States, non-renewable resources are given large subsidies from the government to bolster production, but the same attention and funding is not given to renewable energy. Through lobbying and political media coverage, hydropower has gotten away with being proclaimed “clean” for far too long.

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