When we lived through the cross-border tensions that were dam-driven we thought cooler heads would eventually prevail. But, it has proven not so easy. And who knew there were 10,000 such puzzles out there? Thanks to Fred Pearce, as always for raising our awareness:
Tens of thousands of large dams across the globe are reaching the end of their expected lifespans, leading to a dramatic rise in failures and collapses, a new UN study finds. These deteriorating structures pose a serious threat to hundreds of millions of people living downstream.
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.
Both dams exemplify the potentially dangerous mix of structural decay, escalating risk, and bureaucratic inertia highlighted in a pioneering new study into the growing risks from the world’s aging dams, published in January by the United Nations University (UNU), the academic and research arm of the UN. It warns that a growing legacy of crumbling dams past their design lives is causing a dramatic increase in dam failures, leaks, and emergency water releases that threaten hundreds of millions of people living downstream. Meanwhile, safety inspectors cannot keep up with the workload.
The 20th century was a boom time for dam builders. The peak, particularly in Asia, was from the mid-1950s to mid-1980s, when dams were in vogue to generate hydroelectricity and store water to irrigate crops and keep taps flowing, as well as to smooth out river flow to prevent flooding and improve navigation.
But the boom is over. “A few decades ago, a thousand large dams were being built each year; now it is down to a hundred or so,” report co-author Vladimir Smakhtin of the UNU’s Institute of Water, Environment, and Health in Hamilton, Canada told Yale Environment 360. Most sites sought by dam engineers, such as in narrow valleys, have been plugged. Dams now barricade the majority of the world’s rivers, and can store the equivalent of a sixth of their total annual flow. Meanwhile, environmental and social concerns about flooding land and wrecking river ecosystems have grown, and there are many alternatives for generating low-carbon energy, says Smakhtin…
Read the whole article here.