Half of the world’s 100 largest cities are experiencing high levels of water stress, with 39 of these located in regions of “extremely high water stress”, according to new analysis and mapping.
Water stress indicates that water withdrawals for public supply and industry are near to exceeding available supplies. This condition is often attributed to poor management of water resources, which is exacerbated by climate breakdown.
Watershed Investigations and the Guardian mapped cities onto stressed catchments, identifying Beijing, New York, Los Angeles, Rio de Janeiro, and Delhi among those with extreme stress. London, Bangkok, and Jakarta were classified as highly stressed.
Separate analysis of Nasa satellite data, compiled by scientists at University College London, indicated drying trends over two decades in cities such as Chennai, Tehran, and Zhengzhou. Conversely, Tokyo, Lagos, and Kampala showed strong wetting trends.
Approximately 1.1 billion people reside in major metropolitan areas located in regions experiencing strong long-term drying. This contrasts with about 96 million people in cities within regions showing strong wetting trends. Most cities in notably wetting zones are in sub-Saharan Africa, with Tokyo and Santo Domingo being exceptions. Urban centers with the strongest drying signals are concentrated across Asia, particularly northern India and Pakistan.
Tehran is currently in its sixth year of drought and is reportedly close to “day zero”, where no water would be available for its citizens. In the past, Cape Town and Chennai have also approached “day zero” scenarios. Many rapidly growing cities worldwide are situated in drying zones, potentially facing future water shortages.
Professor Mohammad Shamsudduha of UCL stated that tracking changes in total water storage from space provides an early warning of emerging water insecurity.
The UN announced that the world has entered a state of water bankruptcy, indicating that the deterioration of some water resources has become permanent. Professor Kaveh Madani of the United Nations University Institute for Water Environment and Health noted that poor water management is frequently the main cause of this bankruptcy, with climate breakdown serving as an additional stressor.
The World Bank Group also reported a sharp decline in global freshwater reserves over the past 20 years, with an estimated loss of 324 billion cubic meters annually. These losses affect major river basins across all continents.
By 2055, England may require an additional 5 billion liters of water per day to meet public water supply demand, alongside an extra 1 billion liters daily for other sectors like agriculture and energy. Shamsudduha suggested that groundwater offers the UK a more climate-resilient water supply but cautioned that it requires sustained monitoring and improved management.
Recently, parts of southern England experienced water outages, which South East Water attributed to winter storms. Regulators had previously expressed concerns about the company’s security of supply. The UK government published a water white paper to overhaul the water system, proposing a new chief engineer role, infrastructure checks, and new powers for a water regulator.