Alarming Projections for Global Freshwater Storage
A comprehensive new study has delivered a stark warning: more than half of the planet's freshwater reservoirs could be rendered functionally dead by 2060 due to accumulating sediment. The research, led by Kai Liu at the Chinese Academy of Sciences in Nanjing, China, analyzed over 550,000 reservoirs worldwide using satellite imagery, sedimentation data, and machine learning. The findings reveal that each decade, the world loses over 7 percent of its freshwater storage capacity to sediment buildup—a volume equivalent to more than 36 cubic kilometers annually, comparable to the entire capacity of China's Three Gorges Reservoir.
What Does 'Functionally Dead' Mean?
According to the researchers, a reservoir is considered functionally dead once it is more than half full of sediment. At that point, its ability to store water for drinking, irrigation, hydropower, and other uses is severely compromised. Sediment accumulation occurs naturally as rivers carry silt, sand, and gravel downstream, but dams block this flow, causing material to settle in reservoirs. Over time, this not only reduces water storage but also threatens dam safety and disrupts downstream ecosystems that depend on sediment for nutrient cycling and habitat formation.
Regional Hotspots: Australia and Spain Hit Hardest
The study identifies Australia and Spain as the worst-affected countries. Nearly 85 percent of Australian reservoirs and three-quarters of Spanish reservoirs are projected to surpass their functional lifespans by 2060. In arid regions globally, almost three-quarters of reservoirs may become functionally dead by that time, compared with half of those in humid zones. Namibia faces an especially dire situation, with over 99 percent of its dams in danger, while along the Western Australian coast, the figure approaches 96 percent.
Threats to Water and Food Security
The implications for human populations are profound. The researchers estimate that water supplies to over 2 billion people are threatened by the loss of storage capacity. Additionally, more than a quarter of the world's irrigated agricultural land could be affected, jeopardizing food production in many regions. Ian Wright at Western Sydney University, who was not involved in the study, described the findings as 'very confronting,' particularly as climate change is expected to accelerate sedimentation rates through increased rainfall and erosion.
Mitigation Strategies: Reforestation and Engineering
To address the crisis, the study recommends a combination of upstream and engineering solutions. Upstream measures include reforestation, land stabilization, and erosion control to reduce the amount of sediment entering reservoirs. Engineering solutions such as dredging and the construction of bypass tunnels can remove accumulated sediment, but these come at a significant cost—estimated at up to $100 billion globally. The choice of strategy will depend on local conditions, but the researchers emphasize that proactive management is essential to avoid catastrophic water shortages.
A Call for Urgent Action
The study serves as a wake-up call for governments, water managers, and international organizations. With freshwater already a scarce resource in many parts of the world, the loss of reservoir capacity due to sedimentation compounds the challenges posed by climate change and population growth. Without concerted efforts to reduce sediment inflow and remove existing deposits, the world faces a future where many reservoirs become useless, leaving billions without reliable water supplies. The time to act is now, before the silt settles for good.
This article is based on reporting by New Scientist. Read the original article.
Originally published on newscientist.com
