Nations Slowly Coming To Terms With Huge Costs Of Dealing With Aging, Unsafe Dams

[hatrack]

Engineers have found cracks in the 420-foot-high Kariba Dam on the Zambezi River in Southern Africa. Dmitriy Kandinskiy/Shutterstock

Who would want to live downstream of the 125-year-old Mullaperiyar Dam, nestled in a seismic zone of the Western Ghats mountains in India? The 176-foot-high relic of British imperial engineering cracked during minor earthquakes in 1979 and 2011. According to a 2009 study by seismic engineers at the Indian Institute of Technology, it might not withstand a strong earthquake larger than 6.5 on the Richter scale. Three million people live downriver of the dam. But their demands for it to be emptied are held up by a long-running legal case in the nation’s Supreme Court between Kerala, the state under threat, and Tamil Nadu, the state upstream that operates the dam to obtain irrigation water and hydropower.

Or how about living below the Kariba Dam, built by the British on the Zambezi River in Southern Africa 62 years ago? Back then, it was seen as Africa’s equivalent of the Hoover Dam. But in 2015, engineers found that water released through its floodgates had gouged a hole more than 260 feet deep in the river bed, causing cracks and threatening to topple the concrete dam, which is 420 feet high and holds back the world’s largest artificial lake. Downstream are some 3.5 million people, as well as another giant dam, the Cahora Bassa in Mozambique, that engineers fear would probably break if hit by floodwater from a Kariba failure. Despite the urgency, the $300-million repair work won’t be finished until 2023 at the earliest.

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Dam engineers say the greatest threats for the coming decades are probably in China and India. Both countries have in the past suffered dam failures that killed tens of thousands. In 1979, the disintegration of the Machchhu Dam in Gujarat, India, during a flood, killed as many as 25,000 people. Four years before, the Banqiao Dam in Henan, China, burst, sending a wave of water 7 miles wide and 20 feet high downriver at 30 miles per hour. It killed an estimated 26,000 people directly, including the entire population of the town of Daowencheng. As many as 170,000 more died during an ensuing famine and epidemics. The disaster has been called the deadliest structural failure in history. It was kept a state secret for many years.

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Many old dams are now being abandoned as their reservoirs fill with sediment dropped by the rivers they barricade. An international study in 2014 headed by G. Mathias Kondolf of the University of California, Berkeley, estimated that more than a quarter of the total sediment flow of the world’s rivers is being trapped behind dams. On the Yellow River in China, the world’s siltiest river, the Sanmenxia Dam filled in just two years. India’s reservoirs are losing almost 1.6 million acre-feet of water-storage capacity each year due to sediment build-up, according to officials. The accumulation of sediment makes dams less useful, but sometimes also makes them more dangerous. This is because with less reservoir space, the dams are at greater risk of being overwhelmed during heavy rains. To save their structures, operators are more likely to make abrupt emergency releases down spillways at the height of floods. After Hurricane Mitch ripped through Central America in 1998, several hundred people died in their beds in the Honduran capital of Tegucigalpa when a “wall of water” rushed through the city’s poor riverside communities. Investigators from the U.S. Geological Survey concluded that the “wall” appeared when operators of the city’s two main dams made emergency releases at the height of the flood. The two dams were built only in the 1970s, but had lost much of their capacity to siltation.

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https://e360.yale.edu/features/water-warning-the-looming-threat-of-the-worlds-aging-dams

[HUAJIAO]

1. I 1st thought the headline meant...

dealing with an aging and with unsafe dams.

I thought-- wha,,,,

[Mike 03]

2. And not just aging dams. There are many issues of concern with China's

Three Gorges Dam, and both China and likely India have even bigger projects on the books that look positively insane:

China’s plans for gigantic Brahmaputra dam strains relations with India further

Powerchina’s announcement it will build a mega dam could spur a dam-building race with India, with disastrous consequences for the ecology of the region

https://www.thethirdpole.net/en/regional-cooperation/chinas-plans-for-gigantic-brahmaputra-dam-strains-relations-with-india-further/

I don't have a source handy, but it's been claimed that Three Gorges Dam is so heavy and vast that it has slightly perturbed the rotation of the earth. It's humungus, relatively new, and already shows preliminary signs of architectural strain in satellite photos.

[hatrack]

3. And the insane level of construcion on the Mekong - mostly Chinese, some Laotian . . .

It's going to accelerate saltwater intrusion into the delta in Vietnam, which is the biggest single rice-growing area in the country, AND fuck up the seasonal backup flow that fills the Tonle Sap, which provides the bulk of Cambodia's protein in the form of fish.

A hearty "Well Done!" to all parties concerned.

[NNadir]

4. Well, on the bright side, dam disasters are forgettable.

The Banqiao dam disaster killed between 100,000 and 250,000 people in 1975, just a year before Three Mile Island which killed no one.

Guess which disaster people still talk about?

Dams are fabulous because they're so called "renewable energy. "