Environmental Impacts of Hydropower
HOME · Renewable Energy

What Are the Environmental Impacts of Hydropower?

Electricity is perhaps the most important resource across all human industries everywhere in the world. As climate change and resource conservation become more serious concerns, renewable and clean energy sources are increasingly important. Hydropower is a widely used renewable source of energy. But it is not without environmental impacts across their life cycle; hydropower facilities change their surrounding environment, and these changes affect both humans and wildlife.

What is hydropower?

Hydropower uses water flowing in rivers or stored in dams to generate electricity. The water flowing through dams spin turbine blades, activating huge power generators. The hydroelectric generators then convert the mechanical energy to produce electricity.

In China, the Han Dynasty was the first to use water as a power source between 202BC and 9AD. They used it to mill grain, make paper, and break iron ore. Later in the 18th century, Richard Arkwright used water to power his cotton mill in England. That marked the beginning of the widespread use of hydropower. 

Read more: The History of Hydroelectric Energy.

Humans have tapped into wind and solar energy to create electricity. However, in total electricity production, hydroelectricity still dominates the renewable energy industry in the US, China, South America, Africa, and some parts of Europe.

A non-federal hydroelectric power plant can only be established with a Federal Energy Regulatory Commission license. The commission also monitors existing facilities in conjunction with the US Fish and Wildlife Service and the Environmental Protection Agency. 

Benefits of a hydroelectric power plant

Hydropower represents around 18% of global electricity production. And it accounts for 60% of global renewable electricity capacity. Untapped hydro resources are still in surplus in Latin America. 

China is the largest producer of hydroelectricity in the world. In the United States, hydropower plants produce 17% of electrical energy, while nuclear power plants and fossil fuels make up a larger percentage. Below, we highlight a few reasons why hydropower has gained popularity as a sustainable energy source. 

Less carbon pollution

According to the United States National Hydropower Association, the use of hydropower cuts out 200 million metric tons of carbon yearly. This is equal to the carbon emission of 38 million passenger cars.

The Pacific Northwest, which houses the largest concentration of hydropower in the US, has significantly low carbon emissions. Evidence proves that producing electricity with water power allows for cleaner air and water than fossil fuel energy.

Renewable energy 

Perhaps the most important benefit of hydropower is its renewability. It uses water as a natural resource for replenishing natural river flow and rainfall.

It is important to note that although hydropower uses water, it does not exhaust it. So we do not have to worry about water drying up. Also, unlike natural gas or fossil fuel, we do not have to extract river water; the river’s flow is all that’s needed. It means that we do not generate emissions in the process of sourcing water for hydroelectricity.

Fossil fuel conservation

We save enormous amounts of nonrenewable fossil fuels by using hydropower. The Itaipu Binacional hydroelectric power plant provides 15% and 86% of the electricity consumed in Brazil and Paraguay, respectively. It provided 103.1 million MWh in 2016; an equivalent of 500,000 barrels of oil per day would be needed to provide the same amount of energy2.

Read more: 10 Biggest Hydropower Plants in the World.

Environmental impacts - hydropower 

Photo by Joshua Sukoff on Unsplash

Using hydropower to generate electricity has both benefits and losses for the environment. Hydropower produces cleaner energy compared to burning fossil fuels. However, its intense use of water and land can create imbalances in the ecosystem around the dam area.

Hydropower facilities impact all four kinds of natural habitats associated with it. They are the estuary, the reservoir, the downstream, and the dam. Below are some ways that hydroelectric power affects the environment. 

Land use

Most hydroelectric power plants have a dam and reservoir, which occupy a large land expanse. Suitable hydro plant locations sometimes cover people’s homes, important natural areas, agricultural land, or historical landmarks. The physical appearance of the environment around the dam area experiences significant alteration.

In the US, the construction of surface reservoirs is becoming less common because of the vast amount of resources it consumes. 


Although they built most dams in the United States for municipal water supply, irrigation, and flood control, dams for hydropower generation can cause upstream flooding that would harm native plants, the wildlife habitat, critical natural areas, agricultural land, and humans.

In extreme situations, such flooding incidents can cover people’s homes and displace them from their homes.

Endangering aquatic life

Constructing large hydropower plants usually involves manipulating the natural course of river systems. It often blocks a river’s natural flow and obstructs fish migration routes. Consequently, inhibited fish migration will deplete fish populations over time. A reduced fish population has drastic consequences for both human food supply and marine ecosystem stability. 

Also, the turbines kill some fish that pass through them. According to the Energy Information Administration, fish death by turbines is at 5% to 10% for the best existing turbines. A hydropower plant may use fish ladders to rectify the problem. 

Fish ladders or elevators are devices that help fish move across dams without harm. It works by helping fish like salmon and shad move upstream up to the spawning grounds. These fish ladders, however, may not support massive migrations. 

The United States Department of Energy is working to develop turbines that can reduce fish death to below 2%. But ideally, there should be a 0% turbine death rate because marine life is already facing an environmental crisis with plastic pollution and chemical contamination. 

Disruption of river systems 

Hydroelectric plants alter the natural habitats of freshwater species in their areas. It changes the concentration of nutrients, water temperature, and the river’s flow. Downstream river flow suffers a loss of water and silt loads, reducing water quality. These changes directly affect the ecological characteristics of the rivers that harm native plants and fish species.

Research also shows that dams affect the productivity and stability of estuaries1. A study of two dammed rivers along Mexico’s Pacific coast showed rapid coastal recession. This led to a loss of habitat for aquatic life and a decline in biodiversity.

Greenhouse gas emissions

Hydroelectric generation is not 100% emission-free. Studies have shown that reservoirs created by dammed rivers emit greenhouse gases. Dead plants and other organic materials in the reservoir water decompose, releasing carbon dioxide and methane (a strong greenhouse gas) into the atmosphere. 

Emissions of greenhouse gases can also come from the heating and cooling systems used to maintain the hydroelectric equipment. The amount of greenhouse gas a hydropower reservoir emits may depend on regional factors and the specific location.

Social impact of hydroelectric power plants 

Besides the environmental impact, reservoir construction can have social costs as well. The land needed for building dams may already be occupied by people or affect their livelihood. Research has proven that one consequence of hydroelectric facilities is impaired estuarine livelihoods. This can cause displacement of ethnic groups and human rights violations.


Hydroelectric power plants with big dams have social and environmental impacts. It may not consume non-renewable resources or emit large amounts of greenhouse gas, but its facilities affect land use and rivers.

The NHA of the United States claims the investment of hundreds of millions of dollars every year to enhance the environmental friendliness of hydropower facilities. However, the future of sustainable hydropower seems to be small-scale hydro plants.


E. Ezcurra et al (2019) A natural experiment reveals the impact of hydroelectric dams on the estuaries of tropical rivers. Science Advances. Vol 5. Article 3.


How hydropower can help climate change (2018) United Nations Climate Change News

By Jennifer Okafor, BSc.

Jen’s a passionate environmentalist and sustainability expert. With a science degree from Babcock University Jen loves applying her research skills to craft editorial that connects with our global changemaker and readership audiences centered around topics including zero waste, sustainability, climate change, and biodiversity.

Elsewhere Jen’s interests include the role that future technology and data have in helping us solve some of the planet’s biggest challenges.

Photo by Dan Meyers on Unsplash
Pin Me:
Pin Image Portrait Environmental Impacts of Hydropower
Sign Up for Updates