A new study has discovered that “more than half of large water bodies” are drying up. It pointed a finger at human-driven causes including the climate crisis. However, it also showed that an enduring belief about the way the crisis plays out isn’t entirely true.
‘The climate signal pervades all factors’
Published on 18 May in Science, the University of Colorado Boulder-led study found that 53% of large lakes and reservoirs saw a decline in water storage over 28 years. Over the whole period studied, water bodies lost 603 cubic kilometres of water (145 cubic miles) at a rate of approximately 22 gigatonnes a year.
The results came from a study of Earth’s largest 1,972 lakes and reservoirs, using observations from satellites between 1992 and 2020. Researchers focused on larger freshwater bodies. These provided better accuracy of satellites at a larger scale, and hold particular importance for humans and wildlife.
The team also picked apart natural- and human-driven factors using climate and hydrologic trends. For natural lakes, it found that much of the net loss was attributed to climate warming as well as human water consumption. It attributed storage loss in drying reservoirs to accumulating sedimentation.
Talking to Agence France-Presse (AFP), a professor at the University of Colorado Boulder and co-author of the paper Balaji Rajagopalan said the findings show that the climate crisis is felt everywhere:
The climate signal pervades all factors
Historic lack of interest in lakes
Lead author Fangfang Yao, a visiting fellow at the University of Colorado Boulder, said in a public statement:
Many of the human and climate change footprints on lake water losses were previously unknown, such as the desiccations of Lake Good-e-Zareh in Afghanistan and Lake Mar Chiquita in Argentina.
And it was a lack of focus on lakes and reservoirs that led to the study.
Rajagopalan told AFP that, unlike rivers, lakes aren’t well monitored, despite their critical importance for water security. This is in contrast to rivers, which scientists have studied in great depth. So-called ‘dry up’ events in large water bodies like the Caspian Sea and the Aral Sea, however, signalled to researchers that there may be a wider crisis.
Explaining how two billion people are affected by the findings, Rajagopalan said:
Lakes are in trouble globally, and it has implications far and wide
It really caught our attention that 25 percent of the world’s population is living in a lake basin that is on a declining trend
Surprising finds
The study also produced a surprising finding: lakes in both wet and dry regions of the world are losing volume. This suggested the ‘dry gets drier, wet gets wetter’ climate crisis belief doesn’t always hold.
The University of Colorado Boulder team found losses in humid tropical lakes in the Amazon as well as Arctic lakes, demonstrating a trend more widely spread than previously predicted.
However, although most global lakes were dwindling, nearly a quarter saw significant increases in their water storage. These included the Tibetan Plateau, where the study said “glacial retreat and permafrost thawing” led to greater volumes of water.
Increased water storage in these areas “offset” almost one-third of total dwindling water reserves elsewhere, the study said. It also credited at least some water gains to conservation efforts, and concluded that:
Effective water conservation efforts can help save these water bodies
Nonetheless, it was clear that the climate crisis outstrips all other concerns:
We detect that increasing temperature and [evaporation pressures] are the chief determinants of water loss in 21% of drying natural lakes, a cautionary finding for a projected warmer future, underscoring the importance of accounting for climate change impacts within future surface water resources management.
Additional reporting by Agence France-Presse
Featured image via Arian Zwegers/Flickr (image cropped to 770 x 403) CC 2.0
