Hydroelectric Dams
The Tucuruí Dam Wikipedia
https://en.wikipedia.org/wiki/Tucuru%C3%AD_transmission_line
In a land full of rivers, hydroelectric power may seem like an obvious and promising energy source—especially since it’s often touted as green. No energy source is without environmental problems, and some are worse than others. Hydropower certainly has it]s share, and location plays a major role in how severe those problems are. Unfortunately, the Amazon is one of the worst places for hydropower in terms of environmental impact.
🌳 Reservoirs in the Rainforest
In desert regions, a reservoir created by a dam can be a lifeline. In the Amazon, it’s a natural disaster in slow motion. Flooding from dam reservoirs causes widespread habitat destruction. It’s not just the reservoir roads, transmission lines, and construction infrastructure also fragment ecosystems. Plus, hydroelectricity encourages urbanization, driving further deforestation as it supplies power to growing cities and industries.
🐟 Migratory Fish and Fragmented Rivers
Dams also fragment riverine ecosystems, creating barriers that disrupt the life cycles of migratory fish species like the goliath catfish (Brachyplatystoma sp.). These fish depend on free-flowing rivers to spawn, and many dams have been built without effective ways to allow their passage.
Fish ladders, for example, are often touted as a solution. These detour systems—typically a series of ascending pools—are meant to help fish move upstream (NOAA). Unfortunately, most fish don’t actually use them effectively, and they fail to preserve migratory populations (Adams, 2013).
☁️ Greenhouse Gas Emissions
It may counterintuitive but, hydropower can contribute to climate change. When vast swaths of rainforest are flooded, the submerged vegetation decomposes anaerobically, releasing methane and carbon dioxide. The Amazon, with its immense biomass, produces especially large amounts of greenhouse gases when flooded making it one of the worst-case scenarios for dam-based emissions.
⚙️ Types of Hydropower Matter
There are three major types of hydropower systems, and they differ greatly in their environmental footprint:
Dam and reservoir: The classic large-dam system, with maximum power capacity and maximum destruction. The massive reservoirs behind these dams flood ecosystems and communities alike.
Dam and tunnel: A compromise design where a dam diverts water through a tunnel to turbines downstream. These systems create smaller reservoirs and do less damage, but they also produce less power.
Run-of-the-river: The least destructive method. These systems divert part of a river’s natural flow through turbines without a large reservoir. While least disruptive, they also generate the least electricity and are vulnerable to seasonal flow changes (Killeen, 2023).
📍 Case Study: The Tocantins River
The Tocantins River, in the southeastern Amazon, is the most heavily dammed Amazonian tributary (Goulding et al., 2003). Its largest dam, the Tucuruí Dam, is a massive dam and reservoir system—because neither dam-and-tunnel nor run-of-the-river designs could meet the power demand.
The cost? The reservoir flooded 280,000 hectares of rainforest and displaced 30,000 people, including indigenous communities (Killeen, 2023). It’s one of the starkest examples of how hydropower can bring electricity while destroying the very ecosystems it claims to be helping.
🦟 Bonus Side Effect: Mosquitoes
Hydroelectric dams slow rivers and turn flowing water into stagnant pools—ideal breeding grounds for Anopheles mosquitoes, the primary vectors of malaria. Studies show that dammed rivers can become hotspots for malaria transmission (Kibret et al., 2021), turning a power plant into a public health risk.
🌿 Conclusion
Hydropower may be renewable, but in the Amazon, it’s far from harmless. Between methane emissions, habitat destruction, collapsed fish populations, and disease risk, the environmental cost of dams in the rainforest is far too high to ignore. While alternative designs like run-of-the-river systems offer hope for less destructive solutions, they come with trade-offs in scale.
In the end, the location matters and, the Amazon may be the worst place on Earth to build a dam.
References:
What is a fish ladder? National Oceanic and Atmospheric Administration
https://oceanservice.noaa.gov/facts/fish-ladder.html
Adams, Jill U. (January 25, 2013) Fish Ladders and Elevators Not Working Structures intended to help fish climb upstream aren't doing their jobs Science
https://www.science.org/content/article/fish-ladders-and-elevators-not-working
Killeen Timothy J.(2023) A Perfect Storm in the Amazon Wilderness Second Edition
Goulding Michael, Barthem Ronaldo, Ferreira Efrem (2003) The Smithsonian Atlas of the Amazon
Kibret, Solomon. McCartney, Matthew. Lautze, Jonathon. Nhamo, Luxon. Yan, Guiyun. (June 25, 2021) The impact of large and small dams on malaria transmission in four basins in Africa Scientific Reports