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.

This contains excerpts and paraphrasing of four news stories:

18 Nov 2019 Why some hydropower plants are worse for the climate than coal 23 May 2019 Hydropower is hurting wildlife 11 Jan 2019 the costs of environmental damage and dam removal need to be added into calculations for whether to build a dam or not 19 November 2014 NewScientist article by Peter Hadfield “River of the dammed“,about the Chinese Three Gorges project 2012: the greenhouse gas emissions of hydropower

Alice Friedemann www.energyskeptic.com author of “When Trucks Stop Running: Energy and the Future of Transportation”, 2015, Springer and “Crunch! Whole Grain Artisan Chips and Crackers”. Podcasts: Practical Prepping, KunstlerCast 253, KunstlerCast278, Peak Prosperity , XX2 report

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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

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