Half the world’s 100 largest cities are in high water stress areas, analysis finds | Water
New analysis and mapping has shown that half of the world’s 100 largest cities experience high levels of water stress, with 38 of these located in areas of “extremely high water stress”.
Water stress means that withdrawals for public water supply and industry are close to exceeding available resources; This situation occurs due to poor management of water resources, which is often exacerbated by climate change.
Watershed Investigations and the Guardian mapped cities with stressful basins, finding that Beijing, New York, Los Angeles, Rio de Janeiro and Delhi are among those facing extreme stress, while London, Bangkok and Jakarta are classed as highly stressed.
A separate analysis of NASA satellite data compiled by scientists at University College London shows which of the 100 largest cities have been drying or getting wet over two decades; Places like Chennai, Tehran and Zhengzhou show strong drying trends, while Tokyo, Lagos and Kampala show strong wetting trends. All 100 cities and their trends can be viewed on a new screen interactive water safety atlas.
Approximately 1.1 billion people live in major metropolitan areas in regions prone to strong prolonged drying, while approximately 96 million people live in and around cities in regions prone to strong wetting. However, satellite data is too coarse to show local-scale detail and context.
Most urban areas, especially in water receiving areas, are in sub-Saharan Africa; elsewhere only Tokyo and Santo Domingo in the Dominican Republic. Most urban centers in regions where drying signals are strongest are concentrated in Asia, particularly in northern India and Pakistan.
Tehran, in its sixth year of drought, is dangerously close to “day zero” when water will no longer be available to its citizens, and last year the country’s president, Masoud Pezeshkian, said the city may have to be evacuated if the drought continues. Cape Town and Chennai are approaching day zero, and many of the world’s fastest-growing cities are in drying regions where they may face water shortages in the future.
Mohammad Shamsudduha, professor of water crisis and risk reduction at UCL, said: “By tracking changes in total water storage from space, [the Nasa project] “Grace shows which cities are drying and which are getting wet, providing an early warning of emerging water insecurity.”
On Tuesday, the UN announced that the world had entered a state of water bankruptcy, where the degradation of some water resources has become permanent and irreversible. Prof Kaveh Madani, Director of the Institute for Water Environment and Health at the United Nations University, said water mismanagement was often the main cause of bankruptcies and rarely was climate collapse the only reason: “Climate change is like a recession on top of business mismanagement.”
The World Bank Group is also sounding the alarm. According to the group, which says the planet loses approximately 324 billion cubic meters of freshwater every year, global freshwater reserves have fallen sharply in the last 20 years; This amount is enough to meet the annual needs of 280 million people, roughly the population of Indonesia. Losses are affecting major river basins on every continent.
According to the Environment Agency, by 2055 the UK may need to find 5 billion liters more water per day to meet public water demand; This is more than a third of the 14 billion liters of water currently put into the public water supply. Other water sectors, such as agriculture and energy, may need an additional 1 billion liters of water per day.
Shamsudduha said that “the hidden groundwater resource offers the UK a more climate-resilient water supply”, but added that “without ongoing monitoring and better management, we risk blindly managing it amid increasing development and climate pressures”.
Parts of southern England have experienced water shortages recently, which South East Water attributed to winter storms. But regulators have already written to the company that they have “serious concerns” about security of supply.
On Tuesday the government published a water white paper aimed at overhauling the water system, including creating a new chief engineer role, “MOT checks” on water infrastructure and new powers for a new water regulator.
