Study Projects Over Half of Global Reservoirs Could Lose More Than Half Their Storage to Sediment by 2060

Over half of the planet’s freshwater reservoirs are projected to be functionally dead by 2060 as sediment accumulation reduces their storage capacity, according to a study published in Nature Sustainability. Researchers led by Kai Liu at the Chinese Academy of Sciences analysed more than 550,000 reservoirs using satellite imagery, sedimentation data and machine learning.

They determined that reservoirs lose more than 36 cubic kilometres of storage capacity each year to sediment, a volume comparable to China’s Three Gorges Reservoir.

A reservoir is defined as functionally dead once it is more than half full of sediment. The study projects that nearly 85 per cent of Australian reservoirs and three-quarters of Spanish reservoirs will reach this threshold by 2060. In arid regions nearly three-quarters of reservoirs may become functionally dead by 2060, while half of those in humid zones face the same outcome.

In Namibia more than 99 per cent of dams are projected to lose function, and along the Western Australian coast the figure reaches nearly 96 per cent. Each decade the world loses over 7 per cent of its freshwater storage capacity to sedimentation. The researchers estimate that water supplies for more than 2 billion people and more than a quarter of global irrigated land are threatened by the trend.

Engineering solutions such as dredging and bypass tunnels are estimated to cost up to $100 billion. The study recommends upstream measures including reforestation, land stabilisation and erosion control to reduce sediment inflow. Ian Wright of Western Sydney University, who was not involved in the research, described the findings as “very confronting,” noting that climate change is expected to increase sedimentation rates through greater rainfall.