What Are 3 Bad Things About Hydropower?

Disruption of River Ecosystems

What are 3 bad things about hydropower?

One of the most significant negative impacts of hydropower dams is the disruption they cause to river ecosystems. Dams block fish migration routes and prevent access to spawning grounds upstream (Stanford University, 2020). Fish populations like salmon and steelhead trout require seasonal migration as part of their life cycle. When dams obstruct their passage, it can lead to dramatic declines in their numbers and even localized extinctions (NOAA, 2019).

In addition, dams change the natural flow of rivers and release water from different depths leading to fluctuations in water temperature. This disrupts habitats adapted to historic seasonal patterns. Flooding land near rivers to create reservoirs destroys riparian environments and wetlands that many species rely on.

Methane Emissions

The flooding of land to create reservoirs for hydropower projects results in the anaerobic decomposition of vegetation that was present before inundation. This produces methane, which bubbles up to the surface of the reservoir and releases into the atmosphere. Methane is a potent greenhouse gas, with over 20 times the global warming potential of carbon dioxide over a 100 year period. According to research from the National Renewable Energy Laboratory (https://www.energy.gov/eere/water/tracking-carbon-footprint-hydropower), reservoir surfaces emit over 20% of all methane emissions from natural water bodies. A study cited in Inside Climate News (https://insideclimatenews.org/news/14072023/todays-climate-hydropower-methane-clean-energy/) suggests hydropower may account for at least 1.3% of total global greenhouse gas emissions due to methane production in reservoirs.

Impact on Indigenous Communities

Hydropower dams and reservoirs often have significant negative impacts on indigenous communities. The construction of dams can displace indigenous settlements that have existed for generations, forcing people to abandon sacred sites and ancestral lands (Source). For example, the Site C dam in British Columbia, Canada flooded over 80 miles of the Peace River Valley, displacing First Nations communities.

In addition, the ecological changes caused by dams and reservoirs negatively affect fish populations that indigenous communities rely on for food and cultural practices. The flooding of rivers blocks many fish species like salmon from reaching their natural spawning grounds. This can devastate culturally vital fish populations that indigenous communities have traditionally depended on (Source).


Silt builds up behind dams as slower moving water causes more sedimentation.

Over time, siltation reduces the storage capacity and power generation of dams per “Dealing with Sediment: Effects on Dams and Hydropower Generation”. The extreme case is when reservoirs essentially fill up with silt and become useless.

Sediments can also damage hydropower components like turbines. Fine sediment particles accelerate erosion of turbine parts, reducing efficiency and lifespan per the HydroCoop article on “Dams with Significant Siltation Problems”.

Overall, siltation impacts hydropower production over the long-term. Preventing sediment buildup requires costly dredging and regular maintenance.

Habitat Loss

One of the biggest negative impacts of hydropower is the habitat loss caused by flooding land for reservoirs. According to a 2021 study in Nature, hydropower development causes extensive habitat loss and degradation, triggering biodiversity loss. Reservoirs created by damming flood and inundate large areas of land that were once forests, grasslands, or other wildlife habitats.

This habitat destruction displaces or endangers many plant and animal species that once lived in the area. For example, flooding habitats drives the risk of extinction for endangered species like the Yellow-headed Sideneck Turtle according to researchers. In addition, the fragmentation of rivers by dams prevents many migratory fish and animal species from being able to move through their normal habitats.

Geological Hazards

The immense weight of reservoirs behind hydropower dams can trigger seismic activity and landslides (Source: http://www.waterpowermagazine.com/features/featurehydropowers-inherent-risk-factors-5759530/). The weight stresses local faults, making earthquakes more likely either during initial filling or later operations. Reservoirs also saturate soil on adjacent valley walls, destabilizing them and increasing the risk of landslides. These geologic hazards threaten dams, and dam failure can be catastrophic.

Dam failures cause dangerous flooding downstream, damaging infrastructure, property, and taking lives (Source: https://www.usgs.gov/special-topics/water-science-school/science/hydroelectric-power-water-use). Overtopping, foundation defects, and piping are among the potential modes of failure. While risks can be minimized through quality construction and regular maintenance, hydropower dams fundamentally alter river systems in ways that introduce unavoidable geological hazards.

High Upfront Costs

Hydropower projects require massive upfront investments for dam and turbine construction. According to Statista, the capital costs for a typical hydrothermal power plant in the US can range from $4,022 to $8,099 per kilowatt hour. Construction costs make up the bulk of these capital expenditures. Large-scale hydropower dams and associated infrastructure often run into the billions of dollars.

The high initial investment means hydropower projects also have a long payback period to recoup costs and start generating returns on investment. The payback period can stretch over decades. These high upfront costs make financing challenging, as massive amounts of capital need to be secured early in the project development process.

Impact on Local Communities

One of the most significant negative impacts of hydropower dams is the forced relocation of towns and villages near proposed dam sites. According to a 2022 study from Michigan State University, the construction of hydroelectric dams was associated with decreased population and less economic development in surrounding areas (source). When a dam is built, the rising water of the reservoir can flood inhabited areas, displacing communities that have lived there for generations.

This forced relocation severs people’s connections to their homes and land. As noted by the United States Institute of Peace, dams lead to “loss of spiritual places, fragmentation of societies, and erosion of cultural identity” (source). Sacred sites and historic artifacts of indigenous communities are often lost as well. Experts recommend that hydropower companies prioritize livelihoods, environmental protection, and community engagement from the start to mitigate these disruptions.

Downstream Water Deprivation

Hydropower dams retain water in reservoirs upstream, reducing the natural downstream flow of rivers. According to an article published in The Conversation, “Hydropower dams degrade water quality along rivers. Water that flows downstream from the dams is depleted of oxygen, which harms many aquatic species” (source). Reduced downstream flow can negatively impact ecosystems that depend on natural river flows, harming fish populations and biodiversity.

In addition, decreased water flow downstream can reduce water availability for agriculture, drinking water, and other community needs. A study in Ecological Impacts of Hydropower Dams found “The retention of water in the reservoir means that less water is available downstream for irrigation, navigation, recreation, and maintenance of water quality” (Baird 2021). By altering the natural flow, dams can deprive communities of adequate water resources.


In summary, hydropower can have significant negative impacts that must be carefully weighed against the benefits. Disrupting river ecosystems affects aquatic species and habitats. Methane emissions contribute to climate change. Indigenous communities often face displacement and loss of ancestral lands. Siltation alters downstream environments. New dams flood habitats and block fish migration routes. There are also risks like earthquakes and dam failures.

While hydropower is renewable and low-emission, the environmental and social costs can be high. The impacts on rivers, wildlife, and communities should be thoroughly analyzed before building new dams. With careful siting and mitigation efforts, some impacts may be reduced. However, the damages to ecosystems and people’s livelihoods may still be significant. The pros and cons of hydropower must be carefully evaluated for each project.

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