Aging Dams Pose Growing Threat – Most of Humanity Could Be at Risk

Kariba Dam Zambezi River

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Among the report’s case research studies: Africa’s Kariba Dam, the world’s biggest manufactured tank, impounding 181 km³ of water. Almost $300 million was lent in 2014 to fix the dam, with conclusion anticipated by 2023. The report states “Dams like Kariba will likely continue to operate much longer with recurring investments into repairs despite advanced age as they may be simply too large, risky, and costly to remove.” Credit: Rhys Jones

By 2050, the majority of humankind will live downstream of big dams integrated in the 20th century; Increasingly costly to preserve, professionals anticipate a pattern to decommissioning dams.

By 2050, many people on Earth will live downstream of 10s of countless big dams integrated in the 20th century, much of them currently running at or beyond their style life, according to a UN University analysis.

The report, “Ageing water infrastructure: An emerging global risk,” by UNU’s Canadian-based Institute for Water, Environment and Health, states the majority of the 58,700 big dams around the world were built in between 1930 and 1970 with a style life of 50 to 100 years, including that at 50 years a big concrete dam “would most probably begin to express signs of aging.”

Aging indications consist of increasing cases of dam failures, gradually increasing expenses of dam repair work and upkeep, increasing tank sedimentation, and loss of a dam’s performance and efficiency, “strongly interconnected” symptoms, the paper states.

The report states dams that are well developed, built and preserved can “easily” reach 100 years of service however forecasts a boost in “decommissioning” — a phenomenon getting rate in the U.S.A. and Europe — as financial and useful restrictions avoid aging dams from being updated or if their initial usage is now outdated.

Aging Dams by Region

The issue of aging big dams today challenges a reasonably little number of nations — 93% of all the world’s big dams lie in simply 25 countries led by China and the U.S.A.. Credit: UNU-INWEH

Worldwide, the big volume of water kept behind big dams is approximated at 7,000 to 8,300 cubic kilometers — sufficient to cover about 80% of Canada’s landmass under a meter of water.

The report supplies a summary of dam aging by world area and main function — water system, watering, flood control, hydropower, and leisure.

It likewise information the increasing threat of older dams, the increasing upkeep cost, the decreasing performance due to sedimentation, the advantages of bring back or revamping natural surroundings, and the social effects — advantages and disadvantage — that requirement to be weighed by policymakers choosing what to do. Notably, “the nature of these impacts varies significantly between low- and high-income countries.”

The analysis likewise consists of dam decommissioning or aging case research studies from the U.S.A., France, Canada, India, Japan, and Zambia & Zimbabwe.

Climate modification will speed up the dam aging procedure

“This report aims to attract global attention to the creeping issue of aging water storage infrastructure and stimulate international efforts to deal with this emerging, rising water risk,” states co-author Vladimir Smakhtin, Director of UNU-INWEH.

“Underlined is the fact that the rising frequency and severity of flooding and other extreme environmental events can overwhelm a dam’s design limits and accelerate a dam’s aging process. Decisions about decommissioning, therefore, need to be taken in the context of a changing climate.”

Notes lead author and UNU-INWEH Senior Researcher Duminda Perera: “This problem of aging large dams today confronts a relatively small number of countries — 93% of all the world’s large dams are located in just 25 nations.”

“Large dam construction surged in the mid-20th century and peaked in the 1960s – 70s,” he states, “especially in Asia, Europe and North America, while in Africa the peak occurred in the 1980s. The number of newly-constructed large dams after that continuously and progressively declined.”

Aging Water Infrastructure

Cover of the UNU-INWEH report. Credit: UNU-INWEH

According to the report, the world is not likely to witness another big dam-building transformation as in the mid-20th century, however dams built then will undoubtedly be revealing their age.

China has 23,841 big dams (40% of the world’s overall). And 32,716 big dams (55% of the world’s overall) are discovered in simply 4 Asian nations: China, India, Japan, and the Republic of Korea — a bulk of which will reach the 50-year limit reasonably quickly. The very same holds true of lots of big dams in Africa, South America, and Eastern Europe.

The rate of big dam building and construction has actually dropped considerably in the last 4 years and continues to decrease in part since “the best locations for such dams globally have been progressively diminishing as nearly 50% of global river volume is already fragmented or regulated by dams,” the report states.

As well, there are strong issues relating to the ecological and social effects of dams, and big dams in specific, along with emerging concepts and practices on the alternative kinds of water storage, nature-based services, and kinds of energy production beyond hydropower.

Drivers of dam decommissioning

Public security, intensifying upkeep expenses, tank sedimentation, and remediation of a natural river environment are amongst the factors driving dam decommissioning.

However, most dams eliminated to date have actually been little; decommissioning big dams (specified by ICOLD as 15 or more metres from least expensive structure to crest, or 5 to 15 metres seizing more than 3 million cubic metres) is “still in its infancy, with only a few known cases in the last decade.”

“A few case studies of ageing and decommissioned large dams illustrate the complexity and length of the process that is often necessary to orchestrate the dam removal safely,” includes co-author and UNU-INWEH Adjunct Professor R. Allen Curry, based at the University of New Brunswick.

“Even removing a small dam requires years (often decades) of continuous expert and public involvement, and lengthy regulatory reviews. With the mass ageing of dams well underway, it is important to develop a framework of protocols that will guide and accelerate the dam removal process.”

Decommissioning will likewise have different favorable and unfavorable financial, social, and eco-friendly effects to be thought about in a regional and local social, financial, and geographical context “critical to protect the broader, sustainable development objectives for a region,” the report states.

“Overall, dam decommissioning should be seen as equally important as dam building in the overall planning process on water storage infrastructure developments.”

“Ultimately, value judgments will determine the fate of many of these large water storage structures. It is not an easy process, and thus distilling lessons from and sharing dam decommissioning experiences should be a common global goal. Lack of such knowledge and lack of its reflection in relevant regional/national policies/practices may progressively and adversely affect the ability to manage water storage infrastructure properly as it is aging.”


In addition to the 3 UNU-INWEH professionals, the report was co-authored by Spencer Williams, Graduate Institute of International and Development Studies, Geneva, Switzerland. and Taylor North of McMaster University, Hamilton, Canada.

By the numbers


  • 58,700: big dams signed up in the International Commission on Large Dams (ICOLD) database, a big dam is specified as 15+ meters in height, determined from least expensive structure to crest, or 5 to 15 meters high seizing more than 3 million cubic meters (0.003 km3). Within the 58,700 big dam overall, approximately one in 8 has a 100 million cubic meter (0.1 km3) capability
  • 7,000 to 8,300 km3: volume of water kept behind big dams around the world — about one-sixth of all river discharge worldwide each year — sufficient to cover approximately 80% of Canada’s landmass under a meter of water
  • 50 to 100 years: style life of dams built in between 1930 and 1970 (when most current big dams were developed). Average life span: 50 years
  • ~16,000: big dams 50 to 100 years of ages in North America and Asia
  • ~2,300: big dams 100+ years of ages in North America and Asia

U.S.A. / Canada

  • 56: typical age of 90,580 United States dams (all sizes)
  • 85%+: United States dams in 2020 operating at or beyond their life span
  • 75%: United States dam failures that took place after 50 years of age
  • US$ 64 billion: approximated expense to recondition United States dams
  • 1,275: dams gotten rid of in 21 US states in the last 30 years; 80 gotten rid of in 2017 alone
  • 50%+: big dams in Canada over 50 years of ages

Asia / Pacific


  • 56%: percentage of the world’s big dams found in China and the United States (the top 25 nations represent more than ~93%)
  • 23,841: big dams in China (one of the most of any nation, and 40% of the world’s overall
  • 60%: percentage of the world’s big dams in Asia
  • 55%: percentage of the world’s big dams in simply 4 nations — China, India, Japan, and the Republic of Korea — most of which will quickly reach 50 years of age


  • 1,115+: big dams in India that will be approximately 50 years of ages in 2025
  • 4,250+: big dams in India that will be 50+ years of ages in 2050
  • 64: big dams in India that will be 150+ years of ages in 2050
  • 3.5 million: the approximate variety of individuals at threat if India’s Mullaperiyar dam, developed 100+ years earlier, were to stop working. The dam, in a seismically active location, reveals substantial structural defects and its management is a controversial problem in between Kerala and Tamil Nadu States


  • 100+ years: typical age of big dams in Japan


  • 650: big dams in Australia, half of them 50+ years of ages; 50+ have actually functioned for 100+ years. Portion of Australia’s electrical energy generation from hydropower: 65%

UK / Europe

  • 100+ years: typical age of big dams in the UK
  • ~10%: big dams in Europe 100+ years of ages


  • 2,000: big dams in Africa (¼ of them in South Africa), the least of any continent; mainly utilized for watering

UNU-INWEH is supported by the Government of Canada through Global Affairs Canada, and hosted by McMaster University, Hamilton, Canada.

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