Hydropower's Pollution Paradox: A Deadly Trade-Off?

Hydropower is a low-carbon source of renewable energy and a reliable alternative to electricity generation by fossil fuels. However, hydropower generators and the construction of dams and reservoirs can negatively impact the environment and wildlife. While hydropower is considered safer than fossil fuels, the Banqiao Dam failure in China in 1975, which killed approximately 171,000 people, significantly impacts the death rate per terawatt-hour of electricity produced by hydropower. This event, caused by a typhoon, highlights the potential dangers of hydropower and raises questions about its safety and environmental impact.

Hydropower is a low-carbon source of renewable energy

Hydropower, or hydroelectric power, is one of the oldest and largest sources of renewable energy. It uses the natural flow of water to generate electricity. While hydropower is considered a clean source of energy, it is not without its environmental impacts. Dams, reservoirs, and the operation of hydroelectric generators can affect the environment. For example, dams can obstruct fish migration and alter water temperatures, river flow, and silt loads, which can have negative effects on native plants and animals.

That being said, hydropower is still a much cleaner energy source than fossil fuels. Independent research suggests that the use of hydropower instead of fossil fuels has helped avoid more than 100 billion tonnes of carbon dioxide in the past 50 years. If hydropower were replaced with coal, the International Hydropower Association estimates that global emissions would be at least 10% higher.

The greenhouse gas footprint of hydropower has been questioned, particularly regarding emissions from reservoirs. In certain conditions, reservoirs can release greenhouse gases due to the decomposition of flooded organic material. However, reservoirs can also act as carbon sinks, absorbing more emissions than they emit. The Intergovernmental Panel on Climate Change (IPCC) notes that hydropower has a median greenhouse gas emission intensity of 24 gCO₂-eq/kWh, which is much lower than the median figure for gas, which is 490 gCO₂-eq/kWh.

Hydropower is also a cost-effective source of energy. The global weighted average cost of electricity from hydropower projects in 2022 was $0.061 per kWh, making it the lowest-cost source of electricity in many markets. Hydropower plants can also provide power to the grid immediately, serving as a flexible and reliable form of backup power during outages or disruptions. Additionally, hydropower has a long lifespan, which spreads out the upfront costs over time and reduces the need for frequent replacements or repairs.

In conclusion, hydropower is a low-carbon source of renewable energy that offers a reliable and cost-effective alternative to electricity generation by fossil fuels. It has helped to reduce global carbon emissions and provides a flexible and affordable source of electricity. However, it is important to carefully consider the environmental impacts of hydropower projects and ensure they are responsibly developed and operated to minimise negative consequences.

Hydropower kills fewer people than fossil fuels

Hydropower is a low-carbon source of renewable energy and a reliable and cost-effective alternative to electricity generation by fossil fuels. Fossil fuels are the dirtiest and most dangerous energy sources, and they kill far more people than renewables and nuclear power. In fact, according to an analysis by Oxford University's Our World in Data project, coal is the deadliest power source, causing nearly 25 deaths per terawatt-hour of electricity produced, while oil is the second deadliest, causing more than 18 deaths per terawatt-hour.

The burning of biomass (wood, charcoal, and dung) also causes 4.6 deaths per terawatt-hour, largely due to air pollution. Nuclear energy is the second safest form of electricity, even when accounting for deaths caused by accidents like Chernobyl and Fukushima. Solar is the safest electricity source, followed by wind power.

Hydropower is the renewable energy source with the highest deaths per terawatt-hour produced, mainly due to the Banqiao Dam failure in China in 1975, which killed approximately 171,000 people. However, this is an outlier, and hydropower's death rate since 1965 is 1.3 deaths per TWh.

While hydropower generators do not directly emit air pollutants, the creation of reservoirs and dams can have environmental impacts. Reservoirs can release greenhouse gases due to the decomposition of flooded organic material, and they can also affect water temperatures, chemistry, river flow, and silt loads. Additionally, dams can obstruct fish migration and impact native plants and animals.

Despite these concerns, hydropower generates more than 4,000 terawatt-hours of electricity globally each year, providing clean energy for over 1 billion people. Independent research suggests that using hydropower instead of fossil fuels has helped avoid more than 100 billion tonnes of carbon dioxide in the past 50 years. If hydropower were replaced with coal, the International Hydropower Association estimates that global emissions would be at least 10% higher.

In summary, while hydropower may have environmental impacts, it is still a much safer and cleaner energy source than fossil fuels, which cause significantly more deaths and contribute to climate change.

Hydropower plants can negatively impact aquatic ecosystems

Hydropower is a low-carbon, renewable, and cost-effective alternative to electricity generation by fossil fuels. However, hydropower plants can negatively impact aquatic ecosystems in several ways. Firstly, the construction and operation of dams and reservoirs can disrupt local ecosystems. Dams can block fish migration routes, leading to reduced fish populations. For example, the Chinook Salmon population in the Klamath River on the Oregon-California border has been devastated due to blocked migration routes caused by dams. To mitigate this issue, solutions such as fish ladders, elevators, and "salmon cannons" have been implemented to help fish move around dams.

Secondly, flooding land to create a reservoir can have extreme environmental impacts, including the destruction of forests, wildlife habitats, agricultural land, and scenic lands. This can result in the relocation of communities and the loss of important natural, archaeological, and cultural sites. Additionally, reservoirs can alter natural water temperatures, water chemistry, river flow characteristics, and silt loads. These changes can negatively affect native plants and animals in and around the river.

Thirdly, reservoirs can affect the river downstream. If too much water is stored behind the reservoir, segments of the river downstream can dry out, harming plant and animal life. Reservoir water is typically low in dissolved oxygen and colder than normal river water, and releasing this water downstream can negatively impact plants and animals in those areas.

Furthermore, reservoirs can have an impact on the surrounding environment due to the release of greenhouse gases. In certain conditions, a reservoir will release greenhouse gases due to the decomposition of flooded organic material. Emissions from reservoirs tend to be highest in the first 10 to 20 years and then decrease over time. However, it is important to note that in other conditions, a reservoir may act as a carbon sink, absorbing more emissions than it emits.

While hydropower plants can have negative impacts on aquatic ecosystems, it is important to consider that all energy sources, including renewables, have some environmental impacts. Prudent site selection, innovative technologies, and optimized operations can help to mitigate the negative effects of hydropower projects on aquatic ecosystems.

Hydropower dams can obstruct fish migration

Hydropower is a low-carbon source of renewable energy and a reliable and cost-effective alternative to electricity generation by fossil fuels. It generates more than 4,000 terawatt-hours of electricity globally every year, enough to supply over 1 billion people with clean energy. Independent research suggests that the use of hydropower instead of fossil fuels for electricity generation has helped to avoid more than 100 billion tonnes of carbon dioxide in the past 50 years alone.

However, hydropower turbines kill and injure some of the fish that pass through them. Dams can also block the way for fish that swim up rivers and streams from the sea to reproduce in their spawning grounds. This obstruction of fish migration by hydropower dams has been observed in various parts of the world, including the Kali Gandaki "A" Hydroelectric Dam in Nepal, the Karapiro dam on the Waikato river in New Zealand, and rivers in Australia, France, and North America. The height of the dam can be a factor in the obstruction, but even low weirs can significantly hinder upstream migration.

The impact of these obstructions on fish species can be severe. For example, salmonids in North America were mostly wiped out by dams, along with the livelihoods of people depending on their annual migration. Similarly, dams on the Yangtze River contributed to the extinction of the Chinese paddlefish. In Papua New Guinea, the completion of a single dam on the Purari River is expected to decrease habitat connectivity for freshwater fish in the region by about 80%.

To mitigate the impact of hydropower dams on fish migration, various approaches have been proposed and implemented. These include the construction of fish ladders and elevators to help fish move around or over dams, as well as the implementation of fish passage solutions that consider the unique conditions of each project. Organizations like NOAA Fisheries work to improve fish passage at non-federal hydropower dams and support the sustainability of economically important commercial and recreational fisheries.

Hydropower reservoirs can negatively impact the environment

Hydropower is a low-carbon source of renewable energy and a reliable and cost-effective alternative to electricity generation by fossil fuels. However, hydropower reservoirs can negatively impact the environment in several ways.

Firstly, flooding land to create a reservoir can have a significant environmental impact. It can destroy forests, wildlife habitats, agricultural land, and archaeological sites. In some cases, communities have had to be relocated due to the construction of reservoirs, as seen with the Three Gorges Dam in China. The creation of a reservoir can also obstruct fish migration routes, leading to devastating population declines, such as the Chinook Salmon in the Klamath River on the Oregon-California border.

Secondly, reservoirs can release greenhouse gases, particularly in the first 10 to 20 years after their creation, due to the decomposition of flooded organic material. Methane, a potent greenhouse gas, can form in reservoirs due to decaying organic matter in stagnant water. The construction of large dams also requires large amounts of carbon-intensive concrete, contributing to greenhouse gas emissions.

Thirdly, the operation of dams and reservoirs can alter natural water temperatures, water chemistry, river flow characteristics, and silt loads. These changes can negatively affect native plants and animals in and around the river. For example, reservoir water is typically colder and has lower dissolved oxygen levels than natural river water, which can harm downstream plants and animals when released.

It is important to note that there are strategies to mitigate these environmental impacts, such as reestablishing fish migration routes through fish ladders and trap-and-haul systems, regular flushing of reservoirs to reduce methane buildup, and the use of aerating turbines to increase dissolved oxygen levels. Overall, while hydropower reservoirs can have negative environmental impacts, careful management and innovative solutions can help ensure its long-term sustainability as a viable and responsible energy solution.

Frequently asked questions