What Is The Largest Issue With Hydroelectric Power?

What is the largest issue with hydroelectric power?

Hydroelectric power is a form of renewable energy that generates electricity by using the natural flow of water. Dams store water in reservoirs, which is then released to turn turbines and generate electricity. Hydroelectric power currently provides approximately 16% of the world’s electricity and over 63% of renewable energy. While considered clean and renewable, hydroelectric power has been controversial due to its potential environmental and social impacts. There is an ongoing debate around whether the benefits of hydroelectric dams outweigh the costs. This article examines the largest issues associated with hydroelectric power.

Environmental Impacts

Hydroelectric power can have significant environmental impacts, particularly from the flooding of land and habitats for dam reservoirs. According to the U.S. Energy Information Administration, dams and reservoirs associated with hydropower plants can affect surrounding areas [1]. Flooding land to create a reservoir destroys forests, wildlife habitats, agricultural land, and scenic lands. It also displaces human communities, sometimes without adequate resettlement programs [2].

Reservoirs and stagnant water can negatively impact water quality by increasing algae growth and bacterial contamination. They disrupt water flow, river habitats, and the migration of fish. Reservoirs also cause greenhouse gas emissions, particularly methane from the decomposition of flooded biomass [2].

Displacement of Communities

Hydroelectric dams can often lead to displacement and relocation of communities living near the dam construction site. According to a 2016 study, indigenous populations are especially impacted, as they are “pushed out of their homes” to make way for dam reservoirs. Over the 20th century, an estimated 40 to 80 million people worldwide were displaced due to dam construction (Randell, 2022).

One major example is the Sardar Sarovar dam in India, which displaced over 200,000 people. Many were resettled to areas with infertile land and lack of resources, disrupting their way of life. According to Internal Displacement Monitoring Centre, those affected by dam displacement tend to become impoverished. Overall, the large-scale forced relocation remains one of the most devastating social impacts of building hydroelectric dams.

Altered Landscapes

Hydroelectric power projects often dramatically alter landscapes and geology. Building a dam floods the area upstream, creating a reservoir that submerges forests, wildlife habitat, agricultural land, and sometimes communities (Environmental Impacts of Hydroelectric Power). According to the U.S. Geological Survey, reservoirs created by hydroelectric dams cover almost 1% of the U.S. land area (Hydroelectric Power Water Use).

The creation of reservoirs disturbs natural habitats both upstream and downstream. Upstream habitats are lost as valleys flood, while downstream areas suffer from lack of seasonal flooding, reduced nutrients and reduced sediment transport. This can greatly impact local species that rely on natural seasonal flood cycles and sediment flows (Hydropower and the environment – U.S. Energy Information Administration).

Additionally, the reservoirs themselves create artificial lake habitats, altering local climate, geology and species. The reservoirs may become breeding grounds for mosquitoes and other pests, or provide avenues for invasive aquatic species to spread.

Methane Emissions

Hydroelectric reservoirs can produce significant amounts of methane, a potent greenhouse gas. Methane has a global warming potential 25 times greater than carbon dioxide over a 100-year period Tracking the Carbon Footprint of Hydropower. When areas are flooded to create reservoirs, organic material like vegetation and soil gets submerged. As this material decomposes underwater, it releases methane into the atmosphere. In some tropical regions, methane emissions from reservoirs can be up to 80 times higher than natural lakes Dam Accounting: Taking Stock of Methane Emissions From Reservoirs. Overall, methane from reservoirs may account for 1.3% or more of total global greenhouse gas emissions ‘Giant Methane Factories’: Hydropower Has Long Been Touted as ‘Clean.’ Not So Fast, Some Scientists Say. While hydropower is still considered a clean energy source, methane emissions from reservoirs can significantly offset the climate benefits.

Siltation and Flow

One of the largest issues caused by dams is the interruption of natural sediment transportation down rivers. Dams act as a barrier, blocking the normal flow of sediment downstream. This can alter the natural balance of sediment erosion and deposition in the river, leading to increased erosion downstream of the dam and buildup of sediment behind it.

Sediment buildup in reservoirs reduces storage capacity over time. This loss of capacity requires periodic dredging to maintain the dam’s functionality. However, the release of this built-up sediment if not managed properly, can negatively impact downstream habitats.

Dams also obstruct the natural ebb and flow of rivers. The modified water flow affects nutrients, temperature, and oxygen levels – reducing biodiversity and impacting plants and wildlife well beyond the dam site. Native species that are adapted to historical seasonal flow levels can be especially vulnerable.

Mitigation measures like sediment bypassing, habitat enhancement, and mimicking natural flow variability can reduce some of these impacts. But fundamentally, dams severely disrupt sediment transportation and water flows that are critical to healthy river ecosystems.

Safety Risks

Hydroelectric dams pose potential safety risks due to the catastrophic impacts of dam failures and flooding. Dam failures can occur due to overtopping, foundation defects, piping and seepage issues, and other structural problems. In the event of a dam failure, the downstream flooding could be disastrous, potentially resulting in loss of life and widespread destruction of properties and infrastructure (https://www.hydropower.org/factsheets/dam-safety).

Additionally, many hydroelectric facilities and their supporting infrastructure are located in seismically active regions and may have seismic vulnerabilities. Earthquakes can potentially cause damage to dams and lead to failures. For example, California’s Oroville Dam spillway failure in 2017 following heavy rains demonstrated the risks dams face from natural disasters and their potential impacts on surrounding communities (https://www.pacificorp.com/community/safety/safety-around-dams.html). Rigorous dam safety programs, early warning systems, emergency action plans, and making infrastructure enhancements are crucial for minimizing risks.


Hydroelectric power requires a substantial upfront investment in infrastructure, making costs much higher than other renewable energy sources. According to Statista, the average cost to install 1 kilowatt of hydroelectric capacity globally was $2,881 in 2022.1 For comparison, 1 kilowatt of wind power costs around $1,500 to install and solar PV costs around $1,000.2

The high infrastructure costs of hydroelectric dams and powerhouses, as well as the transmission lines required to connect to the grid, make it one of the most expensive power generation technologies. Hydro Review reports that in 2016, hydro had the highest average construction costs per megawatt of any U.S. power generation technology, costing over $4,000 per kilowatt versus around $1,300 for wind and $1,060 for solar.3

While hydroelectric plants have lower fuel costs compared to fossil fuels, the high initial capital investment often requires significant financing that can take decades to recoup. The costs associated with constructing dams, reservoirs, tunnels, and transmission lines make hydroelectric power amongst the most expensive renewable energy sources.


While hydroelectric power has downsides, there are other renewable energy sources that can provide electricity with less environmental impact. Some great alternatives include:

Solar power harnesses energy from the sun using photovoltaic panels. Solar energy is clean, renewable, and increasingly cost-effective (NRDC). Solar power systems can be installed at both small and utility scales.

Wind power utilizes large wind turbines to generate electricity. Wind is free and abundant, and turbines can often share land with agriculture and livestock (National Grid). Offshore wind farms also utilize open areas on the water.

Geothermal energy taps into underground heat from the earth’s core to produce steam and turn turbines. This heat energy is constantly renewable. While more geographically limited than solar and wind, geothermal can provide constant baseline power (UN).

These clean energy alternatives can meet electricity needs while minimizing habitat disruption and emissions. Energy diversity through a mix of renewables helps build grid resilience. With innovation and scaled deployment, these options keep improving and driving out high-impact sources like large hydropower.


In summary, hydroelectric power faces ongoing debates around its sustainability due to major environmental and social issues. While hydroelectric dams provide renewable energy, they also significantly alter landscapes and ecosystems. Building large dams floods vegetation and habitats, displaces communities, and changes water flows. Dams trap sediment and nutrient flows, causing downstream erosion and ecosystem damage. Additionally, reservoirs emit methane, a potent greenhouse gas. However, proponents argue hydroelectricity still emits far less greenhouse gases than fossil fuels. There are also safety risks of dam failures and natural disasters. While hydroelectricity will likely remain part of the world’s renewable energy portfolio, the environmental and social costs must be weighed against the benefits. Alternatives like solar, wind and geothermal energy may be preferable for sustainability. Overall, the largest issue is that hydroelectric dams disrupt natural ecosystems and human communities, so their development requires careful consideration.

Similar Posts