Tens of thousands of large dams around the world have reached or are approaching the end of their anticipated lifespan. Governments should consider retiring these structures to prevent public safety risks and operating costs from escalating, new research states.
The paper, by the Institute for Water, Environment and Health of the Tokyo-headquartered UN University, the academic arm of the United Nations, shows that most humans are expected to live downstream of large dams by mid-century, exposing them to growing disaster threats as dam structures begin to express signs of ageing.
Like other infrastructure, dams degrade as they age, causing their reliability to decline. A reservoir’s storage capacity, too, shrinks over time as sediment accumulates behind its concrete structures, as does the effectiveness of turbines, electrical generators, and other equipment in hydropower facilities that is subject to wear and tear.
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This means ageing dams incur growing repair and maintenance needs. Climate change accelerates the process, as it exposes infrastructure to increasingly severe weather. With the mass ageing of dams well underway, policymakers need to make decisions about decommissioning these structures and develop a framework of protocols to guide the process sooner rather than later, state the authors.
Research suggests that the service life of dams can reach 100 years if they are well designed, maintained, and monitored. But experts have voiced concerns that the average life expectancy of dams could be much shorter, as low as 50 years.
Most of the world’s 58,700 large dams were built in the 20th century, and most of them are located in Asia. China, India, Japan, and South Korea are home to 55 per cent of all large structures recorded, the majority of which will reach the 50-year threshold in the coming years.
In China, a staggering 30,000 dams are considered ageing, while over 1,100 large dams in India will have turned 50 by 2025, with an estimated 64 large dams to be 150 years old by 2050. Similar trends have been recorded in Africa, South America, and Eastern Europe.
Big question marks
Removing or modifying large dams would prevent rising expenses from straining government budgets. It becomes the best option if economic and practical limitations prevent a structure from being upgraded or if its original use has become obsolete. Despite being a multi-year undertaking, the cost of dam removal is estimated to be an order of magnitude less than that of repairing.
It could also help restore natural riverine ecosystems wiped out as the structures were built, boosting fishery yields and allowing previously displaced communities to reclaim lost farmland.
Yet whether decommissioning is a viable option depends on several factors.
Despite its potential benefits, dam removal can be detrimental to local livelihoods. Especially in developing countries, dams can be essential infrastructure that provides clean water and sanitation, irrigates crops, and alleviates poverty. Nearly 40 per cent of global food production relies on dams for irrigation, and many of these structures serve multiple purposes.
Another problem is, can governments afford retiring dams that are needed in the energy transition? Across the globe, more than 6,300 of these assets are used to generate electricity, and Asia in particular depends on them to bring power to its people.
With 650 GW installed, the region is home to half of the world’s hydropower capacity. China alone hosts 40 per cent of the world’s large dams—most are approaching 50—and India’s current dam construction rate is among the world’s highest.
Experts say that hydropower not only plays a critical role in decarbonising global power production, but it can balance intermittent solar and wind power generation. The International Energy Agency expects dams to remain the world’s largest source of renewable electricity generation for years to come.
Hydropower is the backbone of Southeast Asia’s renewable energy supply.
Zulfikar Yurnaidi, senior research analyst, Asean Centre for Energy
A 2020 study conducted by the International Hydropower Association for the Asian Infrastructure Investment Bank (AIIB), identified 66 hydropower stations across Asia that could be ready for modernisation, and estimated that more than a third of the continent’s capacity will require, or have undergone, modernisation by 2030. The analysis argued that multi-billion-dollar investments are needed to sustain these dams’ contribution to Asia’s renewable energy goals.
Will Henley, the IHA’s head of communications, said while the case for decommissioning cannot be ruled out, upgrading ageing equipment and infrastructure and introducing digital technology can improve a dam’s performance, reduce its environmental impacts and safety risks, and complement other renewables.
To address hydropower’s hefty environmental price tag, dam operators can restore fish passage, prevent vegetation and algae from decaying to curb methane emissions, and remove pollutants from reservoirs.
Henley said rather than replacing ageing dams that are still effective with other energy forms, countries should prioritise hydropower modernisation programmes which combine the strengths of different technologies. Solar panels, for instance, can be deployed on the surface of reservoirs, increasing rather than replacing its generation capacity.
“In some cases, however, decommissioning may be appropriate,” he said. “Removal becomes a judgement on whether the project continues to provide benefits to society, whether there are serious safety concerns that cannot be mitigated, or whether there are disproportionate environmental impacts that cannot be addressed.”
Zulfikar Yurnaidi, senior research analyst at Asean Centre for Energy, a Jakarta-based energy think tank, said while ageing dams posed a growing issue, losing them would mean losing large chunks of the green portion in Southeast Asia’s power mix, critical to hitting the region’s target of sourcing 23 per cent of its primary energy from renewables by 2025. Hydropower currently supplies around 15 per cent of Southeast Asia’s electricity.
“Hydropower is the backbone of Southeast Asia’s renewable energy supply, unaffected by intermittency issues. It will be a challenge for the region to make up for lost hydropower. Options of modernisation should be prioritised whenever possible,” he said.
Vladimir Smakhtin, director at the Canada-based Institute for Water, Environment and Health, noted that while hydropower dams already built would continue producing energy, other clean alternatives were becoming progressively more affordable and widespread.
There are both counterarguments and competition for hydropower in decarbonisation.
Vladimir Smakhtin, director, Institute for Water, Environment and Health, UN University
“There are both counterarguments and competition for hydropower in decarbonisation,” he said. “Decommissioning should be considered in the context of alternatives to a dam’s repair and maintenance or rebuilding, and alternatives that will replace the function of a dam—the hydropower it generates—to be lost with its removal.”
Philip Andrews-Speed, senior principal fellow at the Energy Studies Institute of the National University of Singapore, said replacing hydropower with other clean alternatives would require “a massive amount of investment” in solar and wind as well as battery storage and green hydrogen. “Such a transition would have to be gradual and you would require enough land space or lake and offshore areas to site so much wind and solar,” he said.
Muhammad Rizki Kresnawan, research analyst at Asean Centre for Energy, said rejuvenating ageing dams should be a key priority, with hydropower an important source of clean baseload power. “The question is, is it economically viable? Each case will need to be assessed carefully,” he said.
Global hydropower additions are projected to increase in 2021 and 2022, averaging 28 GW per year. Leading this growth is Asia Pacific amid rising electricity demand, increasing electricity access, and regional electricity trade, with two flagship projects—Wudongde and Baihetan—to be commissioned in China in the coming years.