The Guardian - Half the world’s 100 largest cities are in high water stress areas, analysis finds
“By tracking changes in total water storage from space, [the NASA project] Grace shows which cities are drying and which are getting wetter, offering an early warning of emerging water insecurity.”
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This recent analysis from The Guardian highlights growing concerns about urban water security, revealing that half of the world’s 100 largest cities are now located in regions of high water stress, with 38 of them facing “extremely high” pressure on their water supplies. Cities such as Beijing, Delhi, Los Angeles, New York, and Rio de Janeiro are among those where demand for water is approaching — or in some cases nearing — the limits of what local rivers, reservoirs, and aquifers can reliably provide.
By combining global mapping with satellite observations from NASA’s GRACE mission, researchers have been able to track long-term trends in total water storage across major metropolitan regions. The results show a clear contrast: several cities across Asia and the Middle East, including Chennai, Tehran, and parts of northern India and Pakistan, are experiencing strong drying trends, while others — particularly in sub-Saharan Africa and a few coastal regions — are seeing wetter conditions. Although the satellite data cannot capture local, neighborhood-scale conditions, it provides an early warning signal of where urban water systems may become increasingly vulnerable.
Experts emphasize that these patterns are shaped not only by climate variability, but also by how cities manage their water resources. Rapid population growth, aging infrastructure, and heavy reliance on groundwater can amplify stress in already constrained systems. The World Bank has warned that global freshwater reserves are declining at a pace that affects major river basins on every continent, raising questions about how fast-growing cities will meet future demand for households, industry, and energy.
As urban centers become more interconnected through trade, migration, and shared climate risks, large-scale, data-driven approaches are becoming essential for long-term planning. Initiatives like Canada1Water (C1W) demonstrate how integrated hydrological modelling and climate data can help identify pressures on both surface water and groundwater systems. By supporting scenario-based planning and resilience strategies, C1W reflects the kind of proactive, science-based framework that cities around the world can look to as they work to secure reliable water supplies in an increasingly uncertain future.