The Growing Threat Posed By Ageing Dams

4 Feb 2021 by The Water Diplomat

The world's dam-building spree from 1930 to 1970 is catching up with some nations as they face the risks of a crumbling infrastructure exacerbated by climate change.

"Ageing Water Storage Infrastructure: An Emerging Global Risk", a report published in January by the United Nations University Institute for Water, Environment and Health (UNU-INWEH), identifies that most of the world’s 58,700 large dams were built during that period with a design life of 50 to 100 years, with 93 Percent of them located in just 25 countries. Indeed, China is home to 23,841 large dams, equating to 40 Percent of the world’s total. 55 Percent are concentrated in just four Asian countries: China, India, Japan and South Korea.

Signs of ageing include increasing cases of dam failure, rising repair and maintenance costs, reservoir sedimentation and the loss of dam functionality. “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 ageing process. Decisions about decommissioning, therefore, need to be taken in the context of a changing climate,” says one of the report’s co-authors, Vladimir Smakhtin, Director of UNU-INWEH.

Noting that the pace of large dam construction has dropped dramatically since the 70s, the report highlights that nearly 50 Percent of global river volume is already fragmented or regulated by dams. The drop in dam construction is also due in part to concerns regarding the environmental and societal impacts of large dams, as well as emerging ideas and practices on alternative types of water storage, nature-based solutions and types of energy production beyond hydropower.

While some decommissioning work has been undertaken, particularly in the USA and Europe, the report points to the complex issues surrounding this, saying; “Dam decommissioning should be seen as equally important as dam building in the overall planning process on water storage infrastructure developments.” It also expresses concerns that a lack of knowledge in this respect “may progressively and adversely affect the ability to manage water storage infrastructure properly as it is ageing”.

“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,” adds co-author and UNU-INWEH Adjunct Professor R. Allen Curry.