Half of Global Reservoirs at Risk of Soil Sedimentation by 2060: Impacts and Solutions

More than 50% of the world’s freshwater reservoirs could be “functionally dead” by 2060 due to sediment buildup, warns a comprehensive study.

Dams obstruct silt, sand, and gravel, leading to significant accumulation over time, which diminishes water capacity. This sediment capture can threaten dam safety and adversely affect downstream ecosystems.

Kai Liu and colleagues from the Chinese Academy of Sciences in Nanjing, China, utilized satellite imagery, sediment data, and machine learning techniques to conduct an extensive analysis of over 550,000 global reservoirs.

The research indicates that reservoirs lose more than 36 cubic kilometers of water annually due to sediment accumulation, a volume comparable to that of China’s massive Three Gorges Dam.

A reservoir is dubbed “functionally dead” when sediment occupies over 50% of its volume, significantly impacting its capacity.

Australia and Spain are projected to be the most affected countries, with nearly 85% of Australia’s reservoirs and 75% of those in Spain expected to reach functional obsolescence by 2060.

In arid regions, up to 75% of reservoirs may become functionally dead, while wetlands could see half rendered non-operational. Alarmingly, over 99% of dams in Namibia and nearly 96% along the Western Australian coast are at risk.

Liu et al. estimate a loss exceeding 7% of global freshwater storage capacity each decade, putting more than a quarter of the world’s irrigated land and water supplies for over 2 billion people at risk.

To mitigate this urgent issue, the researchers suggest implementing strategies like upstream reforestation, land stabilization, and erosion control to decrease sediment input into reservoirs. Engineering solutions such as dredging and constructing bypass tunnels are also recommended, with costs potentially reaching $100 billion.

Ian Wright, a professor at Western Sydney University who was not part of the study, points out some “highly contradictory” findings, stressing that climate change may heighten deposition rates due to increased rainfall. The challenge is intensified as many reservoirs are vital for supporting a growing global population, he adds.

“Sedimentation acts like a cancer that gradually diminishes reservoir capacity,” Wright cautions.

He echoes concerns that Australia faces significant deposition issues. “Our soils are extremely fragile, and clearing vegetation in catchment areas increases exposure to erosion, leading to a steady influx of sediment into storage dams,” he states.