Hydropower dams and the ways they destroy things

[ This contains excerpts and paraphrasing of a 19 November 2014 NewScientist article by Peter Hadfield “River of the dammed“. 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.


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.


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