Preface. Hydropower comprises 71% of renewable energy worldwide.  Nations like the U.S. and Europe have dams that have reached the end of their lifespan — more are being torn down than built. In the U.S. 546 dams were removed between 2006 and 2014.

Imagine the potential harm the Pebble mine in Alaska might do to the largest run of sockeye salmon in the world (Cornwall 2020).

This post summarizes eight articles on the damage wreaked by hydropower dams, which are not renewable because they only last 30-200 years.

Destructive hydropower in the news:

2023 The more than 100 hydroelectric projects constructed in the Amazon over the last 50 years have enabled methylmercury levels in fish and humans to rise. Dams built for these projects slow down water flow and allow natural inorganic mercury to settle on the bottom of riverbeds. There, microbes convert it into methylmercury, the most toxic form of the heavy metal, which can make its way up the food chain and cause neurological and behavioral disorders in animals and humans. Symptoms in people include headaches, insomnia, memory loss, tremors, neuromuscular effects and cognitive and motor dysfunction. Artisanal miners in the region also use methylmercury to separate gold from other substances, which contaminates water, soil, and the plants and animals that depend on them. Deforestation in the Amazon leaves ground bare and allows mercury-laden runoff to seep into rivers. Hundreds of new hydro dams are already planned for the Amazon Basin (Langlois J. Why Are Purple Martins Declining in the United States? Smithsonian)

2021 Brazilian hydropower plants are legally required to breed fish in their reservoirs to compensate for damage to local fisheries, which often means importing exotic species. Golden mussels can hitch a ride in the guts of these fish or the water used to transport them. According to Brazil’s Ministry of Mines & Energy, 79 new Amazonian hydroelectric dams are in the planning stages–each one a potential site of a new mussel introduction (Moutinho S. A golden menace: An invasive mussel is devastating ecosystems as it spreads through South American rivers, threatening the Amazon basin. Science 374: 390-393)

Alice Friedemann  www.energyskeptic.com Women in ecology  author of 2021 Life After Fossil Fuels: A Reality Check on Alternative Energy best price here; 2015 When Trucks Stop Running: Energy and the Future of Transportation”, Barriers to Making Algal Biofuels, & “Crunch! Whole Grain Artisan Chips and Crackers”.  Podcasts: Crazy Town, Collapse Chronicles, Derrick Jensen, Practical Prepping, KunstlerCast 253, KunstlerCast278, Peak Prosperity

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2021 Greenhouse gas emissions from reservoirs higher than previously expected

A study in Global Biogeochemical Cycles shows emissions of carbon dioxide, methane, and other greenhouse gases from the world’s water reservoirs are around 29% higher than previous studies, roughly equivalent to 1.07 gigatons of carbon dioxide. Though small compared to the 36 gigatons of greenhouse gas (ghg) emissions from fossil fuels and other industrial sources each year, it’s still more greenhouse gas than the entire country of Germany, the globe’s sixth largest emitter, produces annually. It is also roughly equal in weight to 10,000 fully-loaded U.S. aircraft carriers.

Decomposing plant matter near the bottom of reservoirs fuels the production of methane, a ghg that is 34 times more potent than carbon dioxide over the course of a century and comparable to rice paddies or biomass burning in terms of overall emissions. It accounts for roughly 40% of emissions from water reservoirs. The highest rates of ghg emissions from reservoirs occur in the tropics and subtropics. An estimated 83% of methane emissions occurred within tropical climate zones, where the majority of ongoing and planned new reservoir construction projects are anticipated to occur in coming decades.

Cornwall W. 2020. A dam big problem. A string of catastrophic failures has raised alarm about dams meant to contain muddy mine wastes. Science 369: 906-909.

The dam, a 40-meter wall of rocks and dirt, gave way without warning, unleashing a torrent of mud. Within a day, some 21 million cubic meters of gray goo and water—the tailings waste left behind by 16 years of copper and gold mining at the Mount Polley mine in western Canada—escaped from a holding pond behind the dam, buried a creek, and poured into Quesnel Lake, home to one-third of British Columbia’s legendary Fraser River sockeye salmon.  Since then, in 2015, a tailings dam in Brazil collapsed, unleashing a mammoth mud spill that killed 19 people, contaminated 668 kilometers of river, and reached the Atlantic Ocean. In 2018, a dam failed at a major mine in Australia; and last year, a dam disintegrated at a decommissioned Brazilian iron mine, releasing a torrent that killed 270 people.

There are 3500 to 21000 tailings dams, many at risk of failure.  Engineers fear more catastrophes await, as the world confronts a swelling volume of muddy mine tailings, contained by more and larger dams. Some rise to nearly the height of the Eiffel Tower and hold back enough waste to fill Australia’s Sydney Harbor. “The consequences of a failure are getting much bigger,” says Priscilla Nelson, a geotechnical engineer at the Colorado School of Mines.

Service RF. 2020. Red Alert. Researchers are working to find new uses for red mud, the caustic byproduct of aluminum production. Science 369: 910-911

Aluminum has a dark side: red mud. This brownish red slurry, a caustic mishmash of metal- and silicon-rich oxides, often with a dash of radioactive and rare earth elements, is what’s left after aluminum is extracted from ore. And it is piling up. Globally, some 3 billion tons of red mud are now stored in massive waste ponds or dried mounds, making it one of the most abundant industrial wastes on the planet. Aluminum plants generate an additional 150 million tons each year.

Even when red mud remains contained, its extreme alkalinity can leach out, poison groundwater, and contaminate nearby rivers and ecosystems.

Workers extract the aluminum from bauxite with a combination of treatments, including caustic chemicals, heat, and electricity.

Researchers are looking for ways to use this toxic sludge, but so far it isn’t ideal to make cement, bricks, or extract scandium or other metals economically because the caustic waste destroys key components in their smelters. There are 700 patents on possible uses for red mud, but only 3% of it is recycled.  One major reason is that many schemes envision using red mud to make commodities that are already cheap and produced with methods that have been optimized over a century or more. In addition, red mud isn’t easy to handle.

McGinn, M. 2019. Why some hydropower plants are worse for the climate than coal. Salon

Hydropower can release more greenhouse gases than coal- or oil-burning power plants under certain conditions.  According  to a new study published in Environmental Science Technology, hundreds of active hydropower plants are making a worse impact on the climate than fossil fuels.

Scientists have known for a while now that hydropower facilities release greenhouse gases — mostly methane, but also CO2 and nitrous oxide. But the way they’ve historically calculated a facility’s climate impact has obscured methane’s heat-trapping potency. The new study, which looks at data from thousands of hydropower plants to compare their long- and short-term climate impacts, found that hundreds of active facilities around the world are worse for the climate than coal.

Thieme, M. 2019. Hydropower is hurting wildlife. The Hill.

A new study published in the scientific journal Nature shows that infrastructure and other development has fragmented and disrupted two-thirds of Earth’s longest rivers, mainly with 60,000 dams.  Dams fragment aquatic habitats and block fish migration. Populations of freshwater species have already experienced an 83% decline since 1970, and will probably deplete them further as more dams are built, affecting the tens of millions who depend on fish.

Dams trap sediment and nutrients, keeping them from traveling downriver to fertile deltas that are home to 500 million people. Sediment supply build up deltas is critical in an era of rising sea levels, while nutrients ensure that deltas remain among the most productive agricultural regions in the world.

Moran, E. F. et al. 2018. Sustainable hydropower in the 21st century, Proceedings of the National Academy of Sciences.

Before developing countries build more dams, they need to take the following into account when estimating the cost

• Deforestation
• Loss of biodiversity, especially fish species
• Social consequences, such as the displacement of thousands of people and the financial harm done
• That climate change, especially drought, and evaporation from higher temperatures, which will lead to less water stored for agriculture and electricity
• The cost of removing a dam is extremely high, so high dams wouldn’t be built if this cost were included.  Many new dams in Brazil and other nations will have a short lifespan — just 30 to 50 years

Hadfield, P. 2014.  “River of the dammed“. NewScientist.

Dams typically last 60 to 100 years, but whether Three Gorges can last this long is questionable given the unexpectedly high amounts of silt building up. Since fossil fuels are finite, as is uranium, to keep the electric grid up many see building more dams for hydropower as absolutely essential. Hydropower is also one of the few energy resources that can balance variable wind and solar as well. In addition, climate change is likely to lead to a state of permanent drought and dams could help cope with water shortages.  But dams have a dark side and we should proceed with caution as you’ll see from some of the damage done from the three gorges dam ]

Three Gorges dam stats:

• 13 cities, 140 towns and 1350 villages drowned under the rising water of the Three Gorges dam requiring 1.3 million people to move
• Required  27 million cubic metres of concrete to build the 2-kilometer-long dam.
• Provides 2% of China’s electricity
• 32 turbines, each weighing as much as the Eiffel tower
• Trash litters the water — discarded plastic bottles, bags, algae and industrial crud — because garbage that used to be flushed downriver and out to sea is now trapped and backing up in the Yangtze’s numerous tributaries. It covers a massive area despite 3000 tonnes being collected a day.
• The fish population has crashed:  lower water levels, slower flow, and pollution have crashed the Yangtze’s fish population and also decreasing the productivity of fisheries in the South China Sea.
• Drinking water is being affected because the dam is allowing more seawater than before to intrude into the Yangtze estuary.

Silt will drastically shorten the lifespan of Three Gorges

All dams eventually are rendered useless in 30 to 200 years.  But Three Gorges is silting faster than expected. Far more silt is entering the river and being carried far further than predicted by the models, resulting in silt buildup to depths of up to 60 meters, almost two-thirds the maximum depth of the reservoir itself. The dam continues to accumulate silt at the rate of around 200 million cubic meters a year.

As a result, one of the two navigation channels that pass on either side of an island in the reservoir has been completely blocked, forcing ship traffic in both directions to follow a single channel.

Worse yet, silt is building up at the dam wall. A lot of it has to be cleared by dredgers to make sure it doesn’t interfere with the turbines that generate  China’s electricity and the massive locks that allow ships to travel through.

The only way to slow the process is to build more dams upstream to trap the silt. Many were already being planned. If they are all built, the Yangtze will become a series of dams instead of a river.

Erosion

The filling of the reservoir has also destabilized some of the steep slopes lining the dam. Landslides are common, blocking roads and threatening villages.

This reduces the flow downstream, bringing forward the start of the Yangtze’s natural low-water period. The result is that the Yangtze’s once bountiful floodplain is now drying up. “China’s two largest freshwater lakes – Poyang and Dongting – now find themselves higher than the river,” says Patricia Adams of Probe International, a Canadian environmental foundation that has written a number of critical reports about the Three Gorges dam. “The effect of that is that their water is flowing into the river and essentially draining these very important flood plains.

Like all deltas, the mouth of the Yangtze is a tug of war between deposition and erosion. Between 1050 and 1990, according to a 2003 study, deposition won. During these 900 years the Nanhui foreland, which marks the south bank of the estuary, grew nearly 13 kilometers. But more recently, erosion began to dominate.

The dam has made things even worse by nearly halving the amount of silt entering the delta, leading to a threefold jump in the erosion rate. This could become a major problem for China’s largest city, Shanghai, which is only a meter above sea level, which is expected to rise up to 2 meters over the next century.

List of Serious Problems from The Guardian

• The dam reservoir has been polluted by algae and chemical runoff that would normally have floated away had the dam not been built. Algae and pollution are building up.
• The weight of the extra water is being blamed for earthquake tremors, landslides and erosion of hills and slopes.
• Because of the project’s instability and unpredictability, scientists are calling on the government to: establish water treatment plants, warning systems, shore up and reinforce riverbanks, boost funding for environmental protection and increase benefits to the displaced.
• Some scientists are advocating the reestablishment of ecosystems that were destroyed by the project and are suggesting the additional movement of hundreds of thousands of residents to safer ground.
• Before the project, there were 1,392 fresh reservoirs of water that have become “dead water”, destroying drinking water of over 300,000 people.
• Boat traffic on the Yangtze River has been negatively affected as the depths and shallows of the river have been completely transformed and thousands of boats regularly run aground.
• The design of the project has resulted in damage to the Yangtze River in that water no longer pushes mud and silt downstream but stagnates it above the dam.
• While the current problem is a drought over the past decade floods and droughts have come and gone, the flow control mechanism of the dam project doesn’t seem operational; it does not affect water levels in any way.

Rogner, H.H., et al. 2012. Global Energy Assessment:  Toward a Sustainable Future. Cambridge University Press, International Institute for Applied Systems Analysis  423–512.

Ecosystem impacts usually occur downstream from hydropower sites and range from changes in fish biodiversity and in the sediment load of the river to coastal erosion and pollution.

GHG emissions associated with hydropower are one or two orders of magnitude lower than those from fossil-generated electricity, but can be non-negligible in cases where sites inundate large areas of biomass and consequent CH 4 releases to the atmosphere.

Large hydropower projects requiring large reservoirs and extensive relocation of communities increasingly encounter public resistance and, as a result, face higher costs.

Population density is a major constraint for future development. If a project requires resettlement, the high costs and uncertainty make planning quite difficult.

most of the suitable sites for large hydropower implementation in OECD countries have already been developed