Hydroelectric power has been an important part of renewable energy for a long time. It works by using the natural flow of water to create electricity. From huge projects like the Hoover Dam in the U.S. to smaller, local systems in places like Nepal, hydropower helps supply energy to homes, businesses, and even whole countries. As of 2023, it provides more than 15% of the world’s electricity, showing just how valuable it is.
While it’s a clean and renewable source, it also raises concerns—like its effect on the environment, the people who may be forced to move, and how energy rules and policies are changing. This guide takes a closer look at all of that, helping you understand both the good and the difficult sides of hydropower.
What Is Hydroelectric Power?
Hydroelectric power, or hydropower, is a method of generating electricity by harnessing the energy of moving water. Imagine a river flowing steadily; by constructing a dam across it, we can control the water’s flow. When we release this water, it rushes through turbines, causing them to spin. These spinning turbines are connected to generators, which then produce electricity. It’s a process that transforms the natural movement of water into usable power for our homes and businesses.
There are several types of hydropower systems:
- Impoundment Facilities: These involve large dams that create reservoirs. A classic example is the Hoover Dam in the U.S. When water is released from the reservoir, it flows through turbines, generating electricity.
- Run-of-the-River Systems: These don’t require large reservoirs. Instead, they utilize the natural flow of rivers, diverting a portion through a canal or penstock to spin turbines. This method has minimal environmental impact since it doesn’t significantly alter the river’s flow.
- Pumped Storage: Think of this as a giant battery. During periods of low electricity demand, excess energy is used to pump water from a lower reservoir to an upper one. When demand rises, the stored water is released back down to generate electricity. It’s an efficient way to store and manage energy.
A Glimpse into History
The concept of using water for power isn’t new. In 1870, William Armstrong, a visionary engineer, built the world’s first hydroelectric-powered house in Northumberland, England. He used water from an artificial lake to generate electricity, illuminating his home and showcasing the potential of hydropower.
Global Status and Key Projects
China leads the world in hydropower capacity, boasting over 400 GW, which accounts for about 30% of the global share. This represents a substantial increase from previous years, reflecting China’s commitment to expanding its renewable energy infrastructure. The iconic Three Gorges Dam exemplifies this dedication, significantly contributing to the nation’s energy mix.
Brazil follows with an installed capacity of approximately 110 GW, supplying around 65% of its national electricity needs. The Itaipu Dam, one of the world’s largest hydroelectric projects, plays a pivotal role in this achievement.
Canada’s hydropower capacity stands at about 83 GW, providing roughly 60% of its electricity generation. However, recent droughts have impacted production, leading to increased electricity imports to meet demand.
The United States maintains a capacity of around 80 GW, contributing approximately 7% to its national electricity generation. Projects like the Hoover Dam and Grand Coulee Dam are integral to this output.
India’s hydropower capacity is approximately 50 GW, accounting for about 12% of its electricity generation. The Tehri Dam is a significant contributor to this capacity.
The Pros of Hydroelectric Power
1. It’s Clean and Renewable—and That Really Counts
Hydropower is one of the cleanest energy sources available. Unlike fossil fuels, it doesn’t rely on combustion to generate electricity, so it produces virtually no greenhouse gases during operation. Over its full life cycle—including construction, operation, and decommissioning—hydropower emits approximately 24 grams of CO₂ per kilowatt-hour, according to the Intergovernmental Panel on Climate Change (IPCC).
“In terms of lifecycle emissions, hydropower ranks among the cleanest energy sources available today.”
— Dr. Fatih Birol, Executive Director, International Energy Agency (IEA), 2023
Emissions Comparison (gCO2/kWh)
| Energy Source | Lifecycle Emissions |
| Coal | 820 |
| Natural Gas | 490 |
| Hydropower | 24 |
| Wind | 11 |
| Solar PV | 48 |
2. It Provides Reliable, Around-the-Clock Energy
Unlike solar or wind, which depends on the weather and time of day, hydropower can produce energy 24 hours a day, 7 days a week. That makes it one of the most reliable sources of renewable electricity. Many countries use hydropower as “base load” power—meaning it’s the dependable, always-on electricity that keeps hospitals running, lights on, and factories humming, even when the sun isn’t shining or the wind isn’t blowing.
Even during challenging environmental conditions, such as droughts, hydropower has demonstrated resilience. An analysis by the U.S. Department of Energy revealed that during the most severe droughts between 2001 and 2021, the overall hydropower fleet sustained 80% of its average generation capacity. This capability allowed it to supply flexible power during periods of high energy demand, which shows its reliability even in adverse situations.
Learn More: Pros and Cons of Geothermal Energy
3. It Can Store Energy for When We Really Need It
Hydropower doesn’t just make electricity—it can store it, too. This is where Pumped-storage hydropower (PSH) comes in. During periods of surplus energy production, such as midday when solar panels are most active, excess electricity is used to pump water from a lower reservoir to an upper reservoir. When energy demand increases, like during evening hours, the stored water is released back through turbines to generate electricity.
As of 2023, PSH accounts for approximately 94% of the world’s long-duration energy storage capacity, which shows its pivotal role in maintaining grid stability amid the integration of variable renewable energy sources like solar and wind.
4. It Can Boost Local Economies—Especially in Remote Areas
Building large hydropower projects can bring jobs, roads, and development to underserved regions. However, smaller, community-scale systems might have the most direct human impact.
In Nepal, for example, over 1,000 micro-hydro plants have been constructed, providing electricity to more than 146,500 rural households. These systems have transformed lives—lighting up schools, powering mills, and enabling health centers to refrigerate vaccines.
According to the World Bank, these micro-hydro systems have not only improved education and healthcare access but also reduced indoor air pollution from burning kerosene and firewood.
The Cons of Hydroelectric Power
1. Environmental Disruption
Dams alter the natural dynamics of rivers by obstructing fish migration routes, disrupting breeding cycles, and trapping sediment that would normally flow downstream. This sediment is vital for delivering nutrients essential for agriculture and maintaining healthy wetlands.
Case in Point: The Mekong River Delta
In Southeast Asia, the Mekong River sustains over 60 million people. However, the construction of numerous upstream dams has significantly impacted the region. According to a 2021 study published in Nature Communications, the sediment load delivered to the Mekong Delta has been reduced to approximately 25% of pre-dam levels.
This drastic reduction in sediment adversely affects fisheries and rice farming—both critical to local livelihoods. Fishermen report decreased catches, both in size and quantity, while rice farmers increasingly rely on artificial fertilizers to compensate for the loss of natural nutrients. These gradual yet profound changes are challenging to reverse once dams are in place.
“The river is not bringing sediment; the soil is salinized,” said Cung, a 60-year-old farmer from Vietnam’s Mekong Delta, highlighting the tangible impacts on agriculture.
2. Displacement of Communities
Large hydroelectric projects often necessitate the creation of vast reservoirs, leading to the displacement of entire communities. This upheaval results not only in the loss of homes but also in the erosion of cultural heritage and community bonds.
Case Study: Sardar Sarovar Dam, India
The Sardar Sarovar Dam on the Narmada River has been a focal point of such displacement. Estimates of the number of affected families vary, with figures ranging from approximately 32,000 to 40,000 families across Gujarat, Maharashtra, and Madhya Pradesh.
In 2017, the Supreme Court of India directed that 681 families who had not received compensation be paid ₹6 million ($69,546) each. Additionally, 1,358 families who had previously accepted compensation were awarded an extra ₹1.5 million ($17,389) each.
Despite these measures, reports indicate that many displaced individuals continued to face challenges related to resettlement and rehabilitation. For instance, in 2019, some villagers were still residing in temporary shelters, awaiting proper rehabilitation.
3. High Upfront Costs: Clean Doesn’t Mean Cheap
Building a hydroelectric dam isn’t like installing a few wind turbines. It often takes 5 to 10 years to complete and demands billions of dollars in funding. For instance, China’s Three Gorges Dam took approximately 17 years to complete and cost around $25 billion.
Smaller hydroelectric projects can be more cost-effective and quicker to implement. However, large dams necessitate substantial capital investment and long-term political stability, factors that may not be feasible for every country. A study by the University of Oxford’s Blavatnik School of Government and Said Business School analyzed 245 large dams in 65 countries and found that construction costs were, on average, 90% higher than initial budgets, with construction periods averaging 8.2 years, often extending beyond 10 years.
4. Risk of Catastrophic Failure: When the Unthinkable Happens
Although rare, dam failures are devastating. When they happen, they destroy towns, ecosystems, and lives in mere minutes.
The Banqiao Dam Disaster (China, 1975)
In August 1975, Typhoon Nina brought unprecedented rainfall to Henan Province, China, overwhelming the Banqiao Dam and 61 other dams in the region. The resulting deluge affected over 10 million people, with death toll estimates ranging from 26,000 to 240,000. This catastrophe stands as one of the deadliest dam failures in history.
The Laos Dam Collapse (2018)
More recently, in July 2018, the collapse of a saddle dam at the Xe Pian-Xe Namnoy hydropower project in southern Laos unleashed a torrent of water that inundated villages downstream. The disaster resulted in at least 71 deaths and displaced thousands, underscoring the vulnerabilities associated with dam infrastructure.
Climate Change and Increased Risks
The challenges posed by climate change further exacerbate the risks associated with dam failures. Increased frequency and intensity of extreme weather events, such as heavy rainfall and flooding, place additional stress on aging dam structures. A comprehensive review published in Natural Hazards and Earth System Sciences highlights that climate change impacts could affect dam safety, necessitating multidisciplinary approaches to assess and mitigate these risks.
Real-World Case Studies
Hoover Dam (USA)
The Hoover Dam is more than just a landmark — it’s a symbol of American resilience. Built in the 1930s during the Great Depression, it put thousands to work and brought stability to the Southwest. Today, it still powers over 1.3 million people across Nevada, Arizona, and California.
But the dam’s impact hasn’t been all positive. Years of water shortages and drought in the Colorado River Basin have pushed its output down sharply. In fact, due to record-low water levels in Lake Mead, power generation capacity has dropped by nearly 25% since 2000. Still, the U.S. is investing in upgrading the dam to better integrate it with solar and wind sources, making it part of a flexible, clean energy grid.
Belo Monte Dam (Brazil)
The Belo Monte Dam in Brazil serves as a significant example of the potential risks associated with large-scale hydroelectric projects. Initially designed to generate 11.2 gigawatts (GW) of electricity, the dam has faced challenges that have limited its average output to less than 4 GW. This shortfall is largely due to inconsistent river flows influenced by climate variability.
The construction and operation of the Belo Monte Dam have also led to substantial social and environmental consequences. Over 20,000 Indigenous people and riverine communities were displaced as a result of the project. Additionally, the diversion of the Xingu River’s flow has led to significant ecological impacts, including the drying out of parts of the river and a decline in fish populations that are vital to local diets.
These outcomes highlight the critical need for comprehensive assessments and planning in hydroelectric developments to balance energy production with ecological and social justice.
Bhutan’s Hydropower Model
Hydropower contributes about 14% of Bhutan’s Gross Domestic Product (GDP) and accounts for approximately 26% of the government’s annual revenue. Notably, around 70% of the electricity generated is exported to India, making it Bhutan’s most significant export item.
Despite its economic benefits, Bhutan’s reliance on hydropower exposes it to climate change risks. The country’s mountainous environment and dependence on hydropower make it particularly susceptible to hydrological impacts, affecting both the energy and agriculture sectors.
Recognizing these vulnerabilities, the country is now investing in diversifying its economy and building climate-resilient hydropower.
Learn More: Pros and Cons of Tidal Energy
Future Outlook: Innovation and Policy Trends
1. Floating and Underground Systems
To minimize environmental footprints, engineers are exploring underground pumped storage and floating turbines. For instance, Australia’s Snowy 2.0 project is expanding hydro capacity by connecting existing reservoirs through extensive underground tunnels, aiming for 2.2 GW of capacity.
2. Modernising Ageing Infrastructure
With many hydropower plants over 50 years old, modernization is crucial. Upgrading these facilities enhances efficiency and reliability. The U.S. Department of Energy emphasizes that such improvements can extend plant lifespans and bolster grid resilience.
3. Integration with Smart Grids
Hydropower’s flexibility makes it ideal for integration with smart grids, balancing variable renewables like solar and wind. Advanced control systems enable plants to adjust operations in real-time, ensuring grid stability.
4. Policy Shifts and ESG Metrics
Environmental, Social, and Governance (ESG) standards are reshaping hydropower funding. There’s increased scrutiny of projects’ social and ecological impacts, prompting developers to adopt more sustainable practices.
Actionable Advice: What You Can Do or Support
For Policymakers:
- Prioritise Impact Assessments and Community Consultations: Before approving hydro projects, it’s crucial to conduct thorough environmental impact assessments and engage local communities. For instance, in the Balkans, inadequate consultations have led to protests against dam constructions threatening Europe’s last wild rivers.
- Invest in Modernisation and Sustainable Design: Upgrading existing dams can enhance energy output with minimal environmental disruption. Retrofitting non-powered dams has been identified as a strategy to boost renewable energy without constructing new facilities.
For Consumers:
- Support Utilities Using Responsibly Sourced Hydro: Choose energy providers committed to sustainable hydroelectric practices. This consumer demand encourages companies to adopt environmentally friendly methods.
- Advocate for Energy Transparency and Diverse Renewable Portfolios: Push for clear information on energy sources and support a mix of renewables to reduce reliance on any single source, promoting a balanced and resilient energy grid.
For Investors:
- Seek ESG-Aligned Hydro Projects: Invest in hydroelectric initiatives that meet Environmental, Social, and Governance criteria. Aligned Climate Capital, for example, raised $85 million for clean-energy ventures, emphasizing responsible investments.
- Fund Innovations in Low-Impact Hydro Technology: Support advancements that minimize ecological footprints, such as pumped storage solutions. AGL Energy’s exploration of converting plants to pumped hydro exemplifies this approach.
For Students and Educators:
- Explore Local Water-Energy Issues: Investigate how hydroelectric projects affect your region, considering both benefits and challenges.
- Promote Hydro Literacy through Workshops or Science Fairs: Organise events to educate communities about sustainable hydroelectric practices, fostering informed discussions and future innovations.
Conclusion
Hydroelectric power sits at a fascinating crossroads. It’s a legacy technology still capable of driving the renewable future—if we navigate its trade-offs wisely. By listening to the voices on the ground, respecting ecosystems, and encouraging innovation, hydro can remain a cornerstone of sustainable energy.
As the planet looks to decarbonize, every drop of clean energy counts. But the challenge is making sure it flows fairly, sustainably, and with the least harm to those living along its path.
