Pros and Cons of Hydropower: Environmental and Economic Impacts

Hydropower is one of the oldest and most widely used sources of renewable energy on the planet. Today, hydroelectric power accounts for roughly 17% of the world’s total electricity generation – more than all other renewable technologies combined as of recent years. But despite that impressive footprint, hydropower is not without its complications. From ecological disruption and mass displacement to dam failures and climate-driven risks, this energy source carries a set of tradeoffs that demand careful evaluation. Here’s a clear-eyed look at both sides.

Advantages of hydropower 🔗

Hydropower offers a compelling mix of environmental and economic benefits that have made it a cornerstone of energy policy in dozens of countries.

A genuinely renewable energy source 🔗

Unlike coal or natural gas, flowing water is not consumed in the electricity-generation process – it keeps moving. This makes hydropower a truly renewable, continuously replenishable energy source. As long as rivers flow, hydroelectric plants can operate. That’s a significant advantage over fossil fuels, which are finite and increasingly costly to extract.

Zero operational emissions 🔗

Once a hydropower plant is up and running, it produces no direct air pollution or greenhouse gas emissions during electricity generation. The plants don’t release pollutants into the air and don’t generate toxic by-products during operation. This makes hydropower a meaningful tool in fighting climate change – at least from an operational standpoint.

High efficiency and reliable baseload power 🔗

Hydropower is remarkably efficient at converting an energy input into usable electricity. The global weighted average capacity factor for hydropower sits at approximately 47%, which is considerably higher than solar or wind in most settings. More importantly, unlike solar and wind, hydroelectric plants can generate electricity around the clock – making them a reliable baseload energy source. Storage and pumped-storage systems are even dispatchable, meaning they can ramp output up or down on demand to meet peak electricity needs.

Low running costs and long operational life 🔗

While the upfront construction costs of a hydroelectric dam can be enormous, the long-term operational expenses are low. A large hydropower facility can provide low-cost electricity for 50 to 100 years after being built, with relatively minimal maintenance compared to thermal power plants. This makes hydropower one of the most cost-effective energy investments over its lifetime. Countries like Costa Rica have leveraged this advantage effectively – generating 74% of national electricity from hydropower, achieving strong energy independence and stable electricity prices.

Multi-purpose infrastructure 🔗

Hydropower dams are rarely single-purpose. Beyond electricity, they support irrigation, municipal water supply, flood control, and recreational activities. Research suggests dams can reduce GDP losses from flooding by 12-22%, representing an estimated annual savings of USD 53-96 billion in flood damage globally. This multi-functionality makes the infrastructure investment more economically justifiable for governments, particularly in developing nations.

Complements other renewables 🔗

One of hydropower’s underappreciated strengths is how well it pairs with solar and wind. The flexibility and storage capacity of hydroelectric plants makes them more economical in supporting the use of intermittent renewables like solar energy. When the sun isn’t shining or the wind isn’t blowing, hydroelectric output can be adjusted to fill the gap – stabilizing the overall grid.

Environmental and social challenges 🔗

The advantages above come with a serious caveat: the construction and operation of large hydropower dams can cause significant harm to ecosystems and communities.

Massive land acquisition and habitat loss 🔗

Building a dam requires flooding vast tracts of land to create a reservoir. The Three Gorges Dam in China alone flooded 632 square kilometers, destroying numerous ecosystems and displacing over 1.3 million people. These reservoirs eliminate terrestrial habitats, submerge agricultural land, and permanently alter river landscapes. In many cases, culturally significant and archaeologically important sites are also lost.

Forced displacement of communities 🔗

The human cost of large dam construction is staggering. Over the course of the 20th century, dams displaced an estimated 40 to 80 million people worldwide – often from fertile river valleys where communities had lived for generations. The Akosombo Dam in Ghana, for example, displaced 80,000 people when it flooded the Volta River Basin. Displacement frequently results in long-term economic hardship, loss of livelihoods, and cultural disruption, with indigenous communities often bearing a disproportionate share of the burden.

Ecological disruption of river systems 🔗

Dams fundamentally transform the rivers they are built on. A dam and reservoir can change natural water temperatures, water chemistry, river flow characteristics, and silt loads – all of which affect the ecology and physical characteristics of the river. Fish migration is a particularly serious concern. Species like salmon and shad that travel upstream to spawn are blocked by dams; while fish ladders and elevators help, they are only partially effective.

Turbine passage also kills fish directly. Standard turbines result in fish mortality rates of 5% to 10%, though newer turbine designs developed with U.S. Department of Energy support aim to reduce this to below 2%.

Downstream food security and livelihoods 🔗

The impacts of dams extend well beyond the reservoir boundaries. A 2010 study estimated that 472 million people living downstream from large dams suffer from reduced food security, regular flooding, or impacts on their livelihoods due to altered river flows, reduced sediment loads, and disrupted fisheries. For communities that depend on floodplain agriculture and river fisheries, this can be devastating.

Greenhouse gas emissions from reservoirs 🔗

Hydropower is not entirely emissions-free. When a reservoir is created, flooded vegetation and organic matter decompose underwater, releasing greenhouse gases like carbon dioxide and methane. Research shows enormous variation between reservoirs – some emit negligible amounts while others, particularly in tropical regions with dense vegetation, can be significant emitters. This is an area where environmental impact assessments before dam construction are critically important.

Safety concerns and natural risks 🔗

Beyond ecological and social impacts, hydropower infrastructure carries physical safety risks – risks that are growing more acute as the climate changes.

Dam failure and structural risks 🔗

Dam failures, though relatively rare, can be catastrophic. Hydroelectric dams are statistically more of a frequent threat to human lives than both natural gas and nuclear power, with dams 46 times more likely to experience a disaster than nuclear plants. The 2018 collapse of the Xepian-Xe Nam Noy dam in Laos, attributed to substandard construction and extreme rainfall, released billions of cubic meters of water and caused widespread devastation. A global analysis of dam failures found that poor management, design flaws, and meteorological factors – increasingly influenced by climate change – are the predominant causes of failure in the 21st century.

In the United States alone, as of 2025 there are approximately 16,745 high-hazard potential dams – meaning that if any of these failed, loss of life would likely result. Many of these aging structures require rehabilitation but have not yet received the necessary investment.

Flood risk: protector and threat 🔗

Dams can both reduce and create flood risks depending on how they are managed. When reservoirs are already near capacity during heavy monsoon or rainfall events, operators have limited ability to absorb excess inflow. A recent study assessing 107 hydropower dams over 40 years found that 41% reduced downstream flood risk, while 26% likely worsened it – particularly in mountainous, high-precipitation regions where sudden inflows can overwhelm reservoir capacity. The 2011 Thailand mega-flood, which killed more than 800 people, was linked in part to rigid reservoir operations at major dams.

Sedimentation is another complicating factor. Sediment buildup in a reservoir reduces its available storage volume, meaning it can no longer control large inflows – such as those brought on by unusually heavy rainfall – potentially leading to uncontrolled discharge.

Climate change and long-term viability 🔗

Climate change is reshaping the risk profile of hydropower globally. A WWF study found that 61% of hydropower dams worldwide will be in river basins with high to extreme risk of water scarcity, floods, or both by 2050. Droughts reduce generation capacity – hydropower output has already declined in parts of the southwestern United States, southern Africa, and Brazil due to falling water levels. Meanwhile, more intense storms increase the risk of dam overtopping and failure.

In the Amazon, reduced rainfall linked to climate change is projected to decrease hydropower generation capacity of proposed dams by up to 27% by 2050. This uncertainty makes long-term investment planning for new hydropower projects considerably more challenging, and underscores the need to combine hydropower with other renewable energy sources in national energy portfolios.

Earthquake and geological risks 🔗

Large reservoirs can also induce seismic activity. The immense weight and pressure of water stored in a reservoir can trigger minor earthquakes in geologically sensitive areas – a phenomenon known as reservoir-induced seismicity. Combined with the risk of dam overtopping during actual earthquakes, this adds another layer of risk management complexity for hydropower operators in tectonically active regions.

Weighing the full picture 🔗

Hydropower is neither a clean solution nor a simple villain. It offers real, proven advantages – renewable input, high efficiency, low operating costs, and the ability to stabilize electricity grids. At the same time, it carries serious costs: ecological disruption, forced displacement, greenhouse gas emissions from reservoirs, and growing vulnerability to climate extremes. The challenge for policymakers, engineers, and communities is not whether to use hydropower at all, but how – with rigorous environmental impact assessments, transparent resettlement processes, and adaptive management strategies that account for a changing climate. Smaller-scale and run-of-river designs, which don’t require large reservoirs, represent a promising direction for expanding hydropower with a reduced footprint.

What do you think? Given that climate change is projected to threaten the reliability of over 60% of existing hydropower dams by 2050, should countries continue investing heavily in new large-scale hydropower projects – or prioritize solar and wind instead? And when communities are displaced by dam construction, what level of compensation and resettlement support should be considered adequate?

References

1. https://earth.org/pros-and-cons-of-hydroelectric-energy/
2. https://www.energysage.com/about-clean-energy/hydropower/pros-cons-hydropower/
3. https://www.manufacturing.net/chemical-processing/article/13245967/examining-the-pros-and-cons-of-hydropower
4. https://solartechonline.com/blog/advantages-disadvantages-hydroelectric-power/
5. https://www.hydropower.org/blog/harnessing-the-power-of-dams-for-flood-protection
6. https://www.sciencedirect.com/science/article/pii/S2590332222003694
7. https://www.eia.gov/energyexplained/hydropower/hydropower-and-the-environment.php
8. https://climate.mit.edu/ask-mit/why-arent-we-looking-more-hydropower
9. https://globalresilience.northeastern.edu/laos-dam-collapse-reveals-dangers-of-hydropower-infrastructure-in-a-changing-climate/
10. https://link.springer.com/article/10.1007/s11269-025-04259-7
11. https://damsafety.org/Roadmap
12. https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2025EF006648
13. https://energypedia.info/wiki/Using_Hydro_Power_Plants_for_Flood_Prevention
14. https://wwf.panda.org/wwf_news/?5168466%2FHydropower-projects-threatened-by-increasing-floods-and-droughts-due-to-climate-change-warns-WWF-study=