An alarming new global assessment has found that half of the world’s 100 largest cities are now situated in areas experiencing high levels of water stress, with dozens of major urban centres facing the imminent risk of water supplies approaching or exceeding what is sustainably available, according to a recent investigation published this week. The findings, based on detailed mapping of cities against stressed river catchments and water systems, highlight how urban populations from Asia to the Americas are grappling with mounting pressures on freshwater resources, driven by a mix of climate change impacts and longstanding management challenges.
The analysis, conducted by Watershed Investigations in collaboration with media reveals that 50 out of the 100 biggest cities globally are in regions classified as experiencing “high water stress,” with 38 of those in areas of “extremely high water stress,” where demand for water for households, industry and services is perilously close to exceeding the supply that is renewably available. Cities including Beijing, Delhi, Los Angeles, New York and Rio de Janeiro appear among the worst affected, illustrating how water insecurity crosses economic and geographic boundaries, from rapidly developing Asian metropolises to established cities in wealthier nations.
Water stress occurs when total water withdrawals — for public consumption, agriculture, and industrial use — approach or surpass sustainable limits of the natural water cycle. Experts warn that such conditions leave urban systems vulnerable during periods of drought or fluctuating rainfall, and that the growing gap between demand and supply stresses infrastructure and social systems in profound ways. Researchers note that poor governance and inefficient resource management frequently compound the effects of climate pressures by weakening cities’ capacity to store, allocate and conserve water.
In addition to the spatial mapping of water stress, scientists at University College London analysed two decades of NASA satellite data to chart long-term trends in water storage around the world’s largest urban centres. Their findings show persistent drying in key regions such as northern India and Pakistan, which host numerous rapidly growing cities, while some other cities — mainly in sub-Saharan Africa — exhibit wetter conditions. Cities showing pronounced drying trends include Chennai, Tehran and Zhengzhou, while places such as Tokyo, Lagos and Kampala show signals of increased moisture; however, researchers caution that satellite data lacks the resolution to capture local water availability dynamics in full detail.
The human dimension of the crisis is stark: an estimated 1.1 billion people reside in metropolitan areas located in regions experiencing strong long-term drying, compared with roughly 96 million in and around cities showing wetting trends. Many urban zones facing drying signals also coincide with some of the fastest rates of urban growth in the world, intensifying the strain on existing water infrastructure and raising the spectre of shortages in the decades ahead.
The findings emerge against the backdrop of broader warnings from global institutions. The United Nations this week declared that the planet has entered a state of “water bankruptcy,” where degradation of critical water resources in some regions has become permanent and irreversible, placing additional emphasis on the role of governance failures as much as climate change in driving water insecurity. Meanwhile, reports from the World Bank Group highlight a sharp decline in global freshwater reserves over the past 20 years, with losses amounting to hundreds of billions of cubic metres annually.
As pressure mounts, policymakers and water managers face increasing calls to adopt comprehensive strategies that bolster water conservation, enhance infrastructure, and improve long-term planning to mitigate the risk of shortages that could disrupt economic activity and everyday life in megacities around the world.
