Water scarcity

• 1. Introduction

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  Water scarcity is a crisis already inside billions of lives. About four billion people face severe water shortages for at least one month every year. Half a billion face them all year long. In 2019, the World Economic Forum ranked water scarcity among the largest global risks by potential impact over the next decade. Yet the planet holds 1.4 billion cubic kilometers of water. The paradox at the heart of this story is not a shortage of water on Earth. It is a mismatch between where water exists and where people need it, and between who can reach it and who cannot. Two fundamentally different problems wear the same name. One is physical, rooted in geography and climate. The other is economic, rooted in poverty and neglect. Understanding the difference is the first step toward grasping why some regions run dry while others drown in abundance they cannot drink.

• 2. Two Kinds of Scarcity

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  The International Water Management Institute first defined the distinction between physical and economic water scarcity in a 2007 study. That study looked at how water had been used in agriculture over the previous fifty years. Its question was whether the world could produce enough food for a growing population going forward.

  Physical water scarcity is straightforward in concept. Central and West Asia and North Africa are among the regions projected to have less than 1,000 cubic meters available per person per year. These are areas where natural supply simply falls short of total demand, including the water that functioning ecosystems require. In 2007, the same research found that more than 1.2 billion people were already living in zones of physical water scarcity. Climate change and overdevelopment of hydraulic infrastructure for irrigation and energy have pushed that problem further.

  Economic water scarcity is a different animal. The United Nations Development Programme identifies it as the more common cause of water shortage worldwide. Most countries and regions, the UNDP argues, hold enough water to cover household, agricultural, industrial, and environmental needs. What they lack is the infrastructure or institutional capacity to deliver it. Sub-Saharan Africa is its clearest example. People without reliable access must travel long distances to fetch water that is often unclean. Better infrastructure there, researchers argue, could reduce poverty, lift food production, and improve public health. A quarter of the world's population lives under these conditions.

• 3. Measuring the Crisis

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  Malin Falkenmark developed one of the most widely used tools for measuring water stress. The Falkenmark Water Stress Indicator sets 1,700 cubic meters per person per year as the threshold below which a country or region experiences water stress. Below 1,000 cubic meters, the country faces water scarcity outright. The measure is useful for rough comparisons but has a known weakness: it averages across entire countries, masking local realities. Canada and Brazil both have high overall water supplies yet face significant water-related problems in specific areas.

  A 2018 FAO report offered a more precise definition for the Sustainable Development Goal 6 framework. It defined water stress as the ratio of total freshwater withdrawn by all major sectors against total renewable freshwater resources, after subtracting the flows that freshwater and estuarine ecosystems require to survive. The resulting categories run from below 10 percent (low stress) to above 80 percent (very high stress). Sustainable Development Goal 6, adopted by the United Nations General Assembly in 2015, sets a 2030 target to substantially increase water-use efficiency across all sectors and reduce the number of people suffering from water scarcity.

  A 2016 study traced how the share of people suffering from water scarcity has grown over more than a century. From 0.24 billion people, representing 14 percent of the global population, in 1906, that number climbed to 3.8 billion, or 58 percent, by 2004. By 2025, according to United Nations estimates cited in 2024, the figure had grown further still to 6.2 billion, or 75 percent of the global population, raising concerns about famine and instability. A 2026 report from the UNU Institute for Water, Environment and Health went so far as to say that the terms water stress and water crisis no longer capture the severity of the situation. The UN adopted the term water bankruptcy to signal both the irreversibility and the insolvency of the current state.

• 4. Where the Water Actually Goes

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  Of the total 1.4 billion cubic kilometers of water on Earth, the United Nations estimates that only 200,000 cubic kilometers is freshwater available for human use. A mere 0.014 percent of all water on Earth is both fresh and easily accessible. Of the planet's water, 97 percent is saline. The total easily accessible freshwater takes the form of surface water in rivers and lakes, and groundwater stored in aquifers. Humanity uses and reuses just 5,000 of the roughly 14,000 cubic kilometers available.

  Groundwater has become the main source of clean water globally, supplying nearly half of all drinking water in the world. In the 1960s, improved knowledge, technology, and funding drove what researchers call the agricultural groundwater revolution. By 2010, the world's aggregated groundwater abstraction reached an estimated 1,000 cubic kilometers per year. Irrigation accounts for 67 percent of that total, domestic use for 22 percent, and industrial purposes for 11 percent. Ten countries together account for 72 percent of all abstracted water use. They are India, China, the United States, Pakistan, Iran, Bangladesh, Mexico, Saudi Arabia, Indonesia, and Italy.

  In 60 percent of European cities with more than 100,000 people, groundwater is being used faster than it can be replenished. In northern China, Nepal, and India, irrigation draws on aquifers at unsustainable rates. Mexico City, Bangkok, Beijing, Chennai, and Shanghai are among the cities where aquifer levels have dropped between 10 and 50 meters. A study found that between 6 and 20 percent of roughly 39 million groundwater wells worldwide are at high risk of running dry if local groundwater levels decline by even a few meters.

• 5. Forces Driving Decline

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  Around fifty years ago, people were not as wealthy as today and consumed fewer calories. They required about a third of the volume of water that the world currently extracts from rivers. Today there are seven billion people on the planet. Consumption of water-intensive meat is rising. Industry, urbanization, biofuel crops, and globalized food supply chains all compete for the same water. Producing goods in developing countries for consumption in developed ones means that water use and pollution in poorer regions subsidize higher living standards elsewhere.

  Climate change deepens the problem through several pathways. Rising temperatures increase evaporation and alter precipitation patterns, making droughts and floods more frequent and severe in different regions at different times. Scientists have established a connection between greater hydrologic variability and worsening water availability. One important finding: population change has been found to be four times more important than long-term climate change in its effects on water scarcity. Still, climate change amplifies scarcity in regions where it already exists.

  Deforestation and pollution close the loop. Through the last hundred years, more than half of the Earth's wetlands have been destroyed. The Aral Sea in central Asia, once the fourth largest freshwater lake in the world, lost more than 58,000 square kilometers of area and vastly increased in salt concentration over just three decades. The U.S. Geological Survey estimates that subsidence from groundwater extraction has affected more than 17,000 square miles across 45 U.S. states. Water scarcity and the contamination that follows are already responsible for 80 percent of illnesses worldwide, with diseases such as cholera and typhoid fever among the consequences.

• 6. Flashpoints and Futures

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  A 2019 report by more than 200 researchers found that Himalayan glaciers could lose 66 percent of their ice by 2100. Those glaciers feed Asia's biggest rivers, including the Ganges, Indus, Brahmaputra, Yangtze, Mekong, Salween, and Yellow. About 2.4 billion people live in the drainage basin of the Himalayan rivers. In India alone, the Ganges provides water for drinking and farming for more than 500 million people.

  Disputes over shared water have already escalated. The conflict between Egypt and Ethiopia over the Grand Ethiopian Renaissance Dam intensified in 2020. Egypt views the dam as an existential threat, fearing a reduction in its share of the Nile. In the Rio Grande Valley, intensive agribusiness has deepened disputes over water rights on both sides of the Mexico-United States border. The World Economic Forum estimates that global water demand will surpass global supply by 40 percent by 2030.

  Some countries have shown that separating water use from economic growth is possible. Australia cut water consumption by 40 percent between 2001 and 2009 while its economy grew by more than 30 percent. The International Resource Panel of the UN has recommended that governments move away from mega-projects like dams and pipelines toward holistic management plans that cover the entire water cycle: from source through distribution, economic use, treatment, recycling, reuse, and return to the environment. The UN's FAO projects that by 2025, 1.9 billion people will live in countries or regions with absolute water scarcity, and that two thirds of the world's population could be under stress conditions by then.