• Friday, Feb 26, 2021
  • Last Update : 02:22 pm

UN: World's ageing big dams pose emerging risk

  • Published at 07:50 pm January 23rd, 2021
Ageing Dams
File Photo: General view of plastic trash littering the polluted Potpecko Lake near a dam's hydroelectric plant, in Serbia on January 5, 2021 Reuters

Dozens have suffered major damage or outright collapse over the last two decades in the US, India, Brazil, Afghanistan and other countries

By 2050, more than half the global population will live downstream from tens of thousands of large dams near or past their intended lifespan, according to a UN report released on Friday.

Most of the world's nearly 59,000 big dams -- constructed between 1930 and 1970 -- were designed to last 50 to 100 years, according to research from the UN University's Institute for Water, Environment and Health.

"This is an emerging global risk that we are not yet paying attention to," co-author and Institute director Vladimir Smakhtin told AFP.

"In terms of dams at risk, the number is growing year by year, decade by decade."

A well-designed, constructed and maintained dam can easily remain functional for a century.

But many of the world's major dams fail on one or more of these criteria.

Dozens have suffered major damage or outright collapse over the last two decades in the United States, India, Brazil, Afghanistan and other countries, and the number of such failures could increase, the report warned.

Compounding the risk in ways that have yet to be fully measured is global warming.

"Because of climate change, extreme rainfall and flooding events are becoming more frequent," lead author Duminda Perera, a researcher at the University of Ottawa and McMaster University, said in an interview.

This not only increases the risk of reservoirs overflowing but also accelerates the build-up of sediment, which affects dam safety, reduces water storage capacity, and lowers energy production in hydroelectric dams.  

'Catastrophic consequences'

In February 2017, the spillways of California's Oroville Dam -- the tallest in the US -- were damaged during heavy rainfall, prompting the emergency evacuation of more than 180,000 people downstream.

In 2019, record flooding sparked concern that Mosul Dam, Iraq's largest, could fail.

Ageing dams not only pose a greater risk to downstream populations, but also become less efficient at generating electricity, and far more expensive to maintain. 

Because the number of large dams under construction or planned has dropped sharply since the 1960s and 1970s, these problems will multiply in coming years, the report showed. 

"There won't be another dam-building revolution, so the average age of dams is getting older," said Perera. 

"Due to new energy sources coming online -- solar, wind -- a lot of planned hydroelectric dams will probably never be built."

A global fleet of nearly 60,000 ageing dams also highlights the challenge of dismantling -- or "decommissioning" -- those that are no longer safe or functional.

More than 150 years old

Several dozen have been torn down in the United States, but all of them small, Smakhtin said.

More than 90% of large dams -- at least 15 metres from foundation to crest or holding back no less than three million cubic metres of water -- are located in only two dozen countries.

China alone is home to 40% of them, with another 15% in India, Japan and Korea combined. More than half will be older than 50 within a few years.

Another 16% of the world's dams are in the United States, more than 85% of them already operating at or past their life expectancy. 

It would cost some $64 billion to refurbish them, according to one estimate.

In India, 64 big dams will be at least 150 years old by 2050. In North America and Asia, there are some 2,300 operational dams at least 100 years old. 

Worldwide, there is about 7,500 cubic kilometres of water -- enough to submerge most of Canada by a metre -- stored behind large dams.

Facebook 55
blogger sharing button blogger
buffer sharing button buffer
diaspora sharing button diaspora
digg sharing button digg
douban sharing button douban
email sharing button email
evernote sharing button evernote
flipboard sharing button flipboard
pocket sharing button getpocket
github sharing button github
gmail sharing button gmail
googlebookmarks sharing button googlebookmarks
hackernews sharing button hackernews
instapaper sharing button instapaper
line sharing button line
linkedin sharing button linkedin
livejournal sharing button livejournal
mailru sharing button mailru
medium sharing button medium
meneame sharing button meneame
messenger sharing button messenger
odnoklassniki sharing button odnoklassniki
pinterest sharing button pinterest
print sharing button print
qzone sharing button qzone
reddit sharing button reddit
refind sharing button refind
renren sharing button renren
skype sharing button skype
snapchat sharing button snapchat
surfingbird sharing button surfingbird
telegram sharing button telegram
tumblr sharing button tumblr
twitter sharing button twitter
vk sharing button vk
wechat sharing button wechat
weibo sharing button weibo
whatsapp sharing button whatsapp
wordpress sharing button wordpress
xing sharing button xing
yahoomail sharing button yahoomail