Water scarcity is when a region does not have enough fresh water to meet its needs. There are two types of water scarcity: physical and economic. Physical water scarcity happens when there is not enough water available to meet all needs, including water needed for ecosystems to stay healthy. Areas with desert climates, such as Central Asia, West Asia, and North Africa, often experience physical water scarcity. Economic water scarcity occurs when there is not enough investment in tools or systems to access water from sources like rivers or underground water supplies. It also happens when people lack the skills or resources to meet their water needs. Many people in sub-Saharan Africa face economic water scarcity.

Although there is enough freshwater globally to meet current and future needs, water scarcity happens when water is not available where and when it is needed. This can be caused by population growth, changes in how people live, increased farming, climate change (like droughts or floods), cutting down forests, polluting water, or using water wastefully. These issues can also be influenced by how governments plan and manage water resources.

Water scarcity is studied by looking at many factors, such as soil moisture, water quality, the amount of water ecosystems need, and trade involving water use. Water stress is one way to measure water scarcity and is important for achieving a global goal to ensure clean water for all. About 500 million people live in areas with severe water scarcity all year, and around 4 billion people experience severe water scarcity for at least one month each year. Half of the world’s largest cities face water shortages. Approximately 2.3 billion people live in countries where water scarcity is a problem, meaning each person has less than 1,700 cubic meters of water per year.

Water scarcity can be reduced through better management of water supply and use, cooperation between countries, and water conservation. Increasing access to usable water, such as by reusing wastewater or using desalination (removing salt from seawater), can help. Reducing water pollution and changing how water is traded in global markets are also ways to address water scarcity.

Definitions

Water scarcity refers to the amount of freshwater available and is caused by human activities. It is also called "physical water scarcity." There are two types of water scarcity: physical water scarcity and economic water scarcity. Some definitions of water scarcity consider the needs of the environment, but these definitions may differ between organizations.

Related ideas include water stress and water risk. In 2014, the CEO Water Mandate, part of the UN Global Compact, suggested that these terms should not be used interchangeably. Some groups define water stress as a larger concept that includes water availability, water quality, and access. Access depends on infrastructure and whether people can afford water. This is sometimes called economic water scarcity.

The Food and Agriculture Organization (FAO) describes water stress as the "symptoms" of water scarcity. These symptoms may include conflicts over water use, competition for water, lower reliability of water services, failed harvests, and food shortages. These symptoms are measured using Water Stress Indices.

In 2016, a group of scientists defined water stress as the impact of high water use compared to the amount of water available. This means water stress is driven by demand for water.

A report from the UNU Institute for Water, Environment and Health in 2026 stated that terms like "water stress" and "water crisis" are no longer enough to describe the current global water situation. As a result, the United Nations now uses the term "water bankruptcy" to describe the current state of water systems. This term shows that water systems are both irreversible and insolvent.

Types

Experts have identified two main types of water scarcity: physical water scarcity and economic water scarcity. These terms were first introduced in a 2007 study by the International Water Management Institute. This study looked at how water has been used in agriculture over the past 50 years. It aimed to determine if the world has enough water to grow enough food for a growing population in the future.

Physical water scarcity happens when natural water supplies are not enough to meet all needs, including what ecosystems require to stay healthy. This is common in dry regions. Human actions that affect the climate have made water shortages worse in areas already struggling with scarcity. It can also occur in places where water seems plentiful but is overused, such as when too many water systems are built for farming or energy production. Signs of physical water scarcity include serious harm to the environment, less groundwater, and unequal water distribution among groups.

Areas with very high populations and little rainfall often have less than 1,000 cubic meters of water available per person each year. Examples include parts of Central and West Asia and North Africa. A 2007 study found that over 1.2 billion people live in regions with physical water scarcity. This type of scarcity relates to water needed for growing food, not drinking water, which requires much less.

Some experts suggest a third type of water scarcity called ecological water scarcity. This focuses on the water needed by ecosystems to stay healthy, such as the minimum amount and quality of water that must flow through rivers or wetlands. A 2022 study showed that northern China had more severe ecological water scarcity than southern China. In most areas, water pollution, not human use, was the main cause of this type of scarcity.

Economic water scarcity happens when there is not enough investment in tools or systems to bring water from rivers, underground sources, or other locations. It also means people lack the skills or resources to meet water needs. This forces people to walk long distances to get water for homes and farming, and the water they get is often not clean.

The United Nations Development Programme states that economic water scarcity is the most common type. This is because most countries have enough water for homes, industry, farming, and nature, but lack the resources to deliver it to people. About one-fifth of the world’s population lives in areas with physical water scarcity.

One out of every four people globally is affected by economic water scarcity. This is common in much of Sub-Saharan Africa. Improving water systems in these regions could help reduce poverty. Building better water storage and irrigation systems could increase food production, especially in developing countries that rely on farming with low yields. Providing clean water for drinking would also improve public health. Solving this issue requires more than new systems; it needs economic and political efforts to address poverty and inequality. Lack of funding highlights the need for careful planning.

Most efforts focus on improving water access for drinking and daily use. However, more water is used for activities like bathing, washing clothes, caring for animals, and cleaning than for drinking and cooking. This means focusing only on drinking water may not solve the full problem and could limit possible solutions.

Challenges

There are several ways to measure water scarcity. One method is the water use to availability ratio, also called the criticality ratio. Another is the IWMI Indicator, which measures both physical and economic water scarcity. A third is the water poverty index.

"Water stress" is a term used to describe how much water is being used compared to how much is available. Experts use this term when discussing Sustainable Development Goal 6. A report by the FAO in 2018 defined water stress as the ratio of total freshwater used by all major sectors to total renewable freshwater resources, after considering the water needed to protect ecosystems. This calculation divides the total freshwater used by the difference between total renewable water and the water needed for ecosystems. Earlier, under Millennium Development Goal 7, water stress was described as the percentage of total water resources used, without considering ecosystem needs. This definition includes categories: below 10% is low stress; 10-20% is low-to-medium; 20-40% is medium-to-high; 40-80% is high; and above 80% is very high.

Indicators help measure water scarcity. One method is to calculate how much water is available per person each year. The "Falkenmark Water Stress Indicator" was created by Malin Falkenmark. This indicator states that a country or region has "water stress" when annual water supplies fall below 1,700 cubic meters per person per year. Between 1,700 and 1,000 cubic meters per person, water shortages may happen sometimes. If supplies drop below 1,000 cubic meters per person, the area faces "water scarcity." However, this indicator does not fully explain the causes of water scarcity.

Another way to measure water scarcity is by looking at renewable freshwater. This metric helps describe the total water resources available in a country. It can show whether a country might face physical water scarcity. However, this metric has a problem: it is an average. Water is not distributed evenly around the world each year, so renewable water resources change yearly. This metric does not explain how easy it is for people, homes, businesses, or governments to access water. Also, it describes a country as a whole, not specific areas within it. For example, Canada and Brazil have large water supplies but still face water-related challenges. Some countries in Asia and Africa have limited freshwater resources.

Water scarcity assessments need to include many types of information. These include data about green water (water stored in soil), water quality, environmental water needs, globalization, and virtual water trade. Since the early 2000s, assessments have used more complex models. These models use tools that analyze spatial data. Examples include green-blue water scarcity, footprint-based water scarcity assessments, and the cumulative abstraction to demand ratio, which considers changes over time. Other examples are LCA-based water stress indicators and integrated water quantity–quality environment flow. Since the early 2010s, assessments have also looked at both the amount and quality of water.

A successful assessment requires experts from different scientific fields. These include hydrology (water movement), water quality, aquatic ecosystem science, and social science.

Available water

The United Nations estimates that only 200,000 cubic kilometers of the total 1.4 billion cubic kilometers of water on Earth is freshwater that humans can use. Less than 0.014% of all water on Earth is both fresh and easy to reach. Of the remaining water, 97% is saltwater, and nearly 3% is hard to access. Freshwater available for humans makes up about 1% of Earth’s total water. The amount of freshwater that is easily accessible is 14,000 cubic kilometers. This includes surface water, such as rivers and lakes, and groundwater, like water stored in aquifers. Of this total, humans use and reuse about 5,000 cubic kilometers. Globally, there is enough freshwater to meet the needs of the current world population of 8 billion people. There is also enough to support population growth to 9 billion or more. However, water is not equally available in all areas, and some groups use more than others, making it a scarce resource in certain regions.

Rivers and lakes are common sources of surface freshwater. Other sources, such as groundwater and glaciers, are becoming more important for providing clean water. Groundwater is water found below Earth’s surface and can be accessed through springs or wells. These underground water sources are called aquifers. It is becoming harder to use traditional water sources because of pollution and climate change. As a result, people are relying more on groundwater and other resources. Population growth is increasing the demand for these types of water supplies.

Scale

In 2019, the World Economic Forum listed water scarcity as one of the most serious global risks in terms of how much it could affect the world over the next ten years. Water scarcity can happen in different ways. One way is when there is not enough water to meet people’s needs, either completely or partially. Other examples include competition between groups for water quantity or quality, arguments between people who use water, the loss of groundwater that cannot be recovered, and harm to the environment.

About half of the world’s population currently faces severe water shortages for at least part of the year. Half a billion people around the world experience severe water scarcity all year. Half of the world’s largest cities have water shortages. Nearly two billion people do not have access to clean drinking water. A study from 2016 found that the number of people affected by water scarcity increased from 0.24 billion (14% of the global population) in 1906 to 3.8 billion (58%) in 2004, according to United Nations estimates from 2024. This number later rose to 6.2 billion (75% of the global population) in 2025, which has raised concerns about food shortages and instability. The study used two terms to describe water scarcity: shortage, which happens when there is not enough water for each person, and stress, which occurs when people use more water than is available.

During the 20th century, water use grew faster than the population. Water use is expected to increase by 50% in developing countries and 18% in developed countries by 2025. For example, Africa is predicted to have 75 to 250 million people without access to fresh water. By 2025, 1.8 billion people will live in areas with absolute water shortages, and two-thirds of the world’s population may face water stress. By 2050, more than half of the world’s population will live in areas with water stress, and an additional billion people may not have enough water, according to research from MIT.

As global temperatures rise and water demand increases, six out of ten people are at risk of facing water stress. The drying of wetlands, which has affected about 67% of wetlands worldwide, has directly increased the number of people at risk of water stress. As water demand and temperatures rise, it is likely that two-thirds of the population will live in water-stressed conditions by 2025.

According to a United Nations projection, about 4.5 billion people could be affected by a water crisis by 2040. As the population grows, more food will be needed, which will require more water to grow crops. The World Economic Forum estimates that global water demand will exceed global water supply by 40% by 2030. Increased water use and population growth will create a water crisis where there is not enough water to meet basic needs. These problems are not only about the amount of water but also the quality of water.

A study found that 6-20% of about 39 million groundwater wells are at high risk of running dry if groundwater levels drop by just a few meters. In many areas, and possibly more than half of major aquifers, this could happen if groundwater levels continue to decline.

Impacts

Factors that people can control, such as how water is managed and shared, can lead to water shortages. A 2006 United Nations report highlights that problems with leadership and decision-making are central to the water crisis. The report states: "There is enough water for everyone." It also explains: "Not having enough water is often because of poor management, dishonest actions, weak systems, slow decision-making, and not enough investment in people or physical structures."

Economists and others have pointed out that the lack of clear ownership rights, government rules, and financial support for water use have contributed to the current situation. These issues lead to water being too cheap and used too much, which some people believe supports private companies managing water.

The clean water crisis is a growing problem worldwide, affecting about 785 million people. About 1.1 billion people do not have access to clean water, and 2.7 billion people face water shortages for at least one month each year. Around 2.4 billion people deal with water that is polluted or lacks proper sanitation. Polluted water can cause deadly diseases like cholera and typhoid fever, which are responsible for 80% of illnesses globally.

Using water for homes, food production, and industry has major effects on ecosystems worldwide, even in areas not considered water-scarce. Water shortages harm the environment in many ways, such as damaging lakes, rivers, wetlands, and other freshwater sources. This often leads to overuse of water in farming areas. Overuse can increase salt levels, pollute water with nutrients, and reduce wetlands and floodplains. It also makes it harder to restore water flow in urban streams.

Over the past 100 years, more than half of the Earth’s wetlands have been destroyed. Wetlands are important habitats for many animals, including mammals, birds, fish, amphibians, and insects. They also help grow crops like rice and provide natural water filtering and protection from storms and floods. Freshwater lakes, such as the Aral Sea in Central Asia, have also suffered. Once the fourth-largest freshwater lake, it has lost over 58,000 square kilometers of area and has become much saltier over three decades.

Subsidence, or the sinking of the ground, is another result of water shortages. The U.S. Geological Survey estimates that subsidence has affected more than 17,000 square miles across 45 U.S. states, with 80% caused by using groundwater.

Plants and animals depend on enough freshwater. Wetlands, marshes, and areas near rivers are especially reliant on steady water supplies. Forests and other land areas are also at risk as water becomes less available. In wetlands, land has often been taken for human use, and in other areas, less water flows into ecosystems because water is redirected for human needs.

Other effects include increasing conflicts between people who use water and competition for limited water supplies. Examples of such conflicts include food shortages in the Middle East and North Africa and disputes over water resources in different regions.

Causes and contributing factors

About fifty years ago, many people believed water was an unlimited resource. At that time, the world had fewer than half as many people as today. People were not as wealthy, ate less food, and used less water to grow their food. They used about one-third of the water we now take from rivers. Today, competition for water is much greater. This is because the world now has about 7 billion people, and more water is needed for food production as people eat more water-heavy foods like meat. Industry, cities, biofuel crops, and water-heavy foods also use more water. In the future, even more water will be needed for food because the world’s population is expected to reach 9 billion by 2050.

In 2000, the world had 6.2 billion people. The United Nations predicts that by 2050, there will be 3.5 billion more people, mostly in countries already struggling with water shortages. This will increase water demand unless more water is saved and reused. The World Bank says that getting enough water to grow food will be a major challenge in the coming decades. It will be important to balance water use with ways to protect water supplies. At the same time, changes caused by climate change and other factors must be considered.

In 60% of European cities with more than 100,000 people, groundwater is being used faster than it can be refilled.

The growing population increases competition for water, which is draining many of the world’s major underground water sources. This happens for two reasons: direct human use and farming that uses a lot of water. Millions of pumps around the world are removing groundwater, especially in dry areas like northern China, Nepal, and India. This is happening faster than the water can be replaced. Cities like Mexico City, Bangkok, Beijing, Chennai, and Shanghai have seen groundwater levels drop by 10 to 50 meters.

Until the 1960s, groundwater was not widely used. Advances in knowledge, technology, and funding made it easier to use groundwater instead of surface water. This helped increase food production and development in rural areas. Groundwater provides nearly half of the world’s drinking water. Most aquifers hold large amounts of water, which can be used during dry periods. This is vital for people who rely on groundwater instead of rain or surface water. In 2010, the world used about 1,000 km³ of groundwater each year. Of this, 67% was used for farming, 22% for homes, and 11% for industry. The top ten countries using groundwater account for 72% of all groundwater use. These countries are India, China, the United States, Pakistan, Iran, Bangladesh, Mexico, Saudi Arabia, Indonesia, and Italy.

Groundwater is plentiful, but some sources are not being replenished quickly enough. Using water from sources that cannot be refilled could run them out if not managed carefully. Using too much groundwater can also lower water quality over time. Groundwater systems often show signs of reduced water levels, natural outflows, and water quality. Groundwater shortages can lead to higher pumping costs, changes in water salinity, and land sinking. They can also harm springs and reduce water flow in rivers.

The main cause of water shortages is the large amount of water used in farming, raising livestock, and industry. People in developed countries use about 10 times more water daily than those in developing countries. Much of this is from water-heavy industries and agriculture, such as growing fruit, oilseed crops, and cotton. Many of these processes are global, meaning water use and pollution in developing countries often support goods used in developed countries.

Many underground water sources are being used too quickly and are not refilling fast enough. This does not mean all fresh water is gone, but much of it has become polluted, salty, or unusable for drinking, farming, or industry. To avoid a global water crisis, farmers must produce more food to meet growing needs. At the same time, industries and cities must find ways to use water more efficiently.

Businesses like tourism are growing, which increases the need for more water and better sanitation. This can put more pressure on water resources and natural ecosystems. The world’s energy use is expected to grow by about 50% by 2040, which will also increase the need for efficient water use. Some water use may shift from farming to industry because power plants use water for cooling and steam generation.

Water pollution is when water becomes dirty, making it hard to use. It is usually caused by human activities. Water pollution can harm lakes, rivers, oceans, aquifers, reservoirs, and groundwater. It happens when harmful substances mix with water. These substances come from four main sources: sewage, industry, farming, and stormwater runoff. Water pollution can damage ecosystems, spread diseases through drinking or irrigation water, and reduce the benefits water provides, like clean drinking water.

Pollution can come from two types of sources: point sources, which have one clear cause (like a factory or oil spill), and non-point sources, which are spread out (like farm runoff). Pollution can take many forms, such as toxic chemicals, changes in water temperature, or harmful bacteria. A common cause of pollution is when industries use water for cooling, which warms it and harms nearby water sources.

Climate change may greatly affect water resources worldwide because of the connection between weather and water cycles. Higher temperatures will increase evaporation and rainfall, but rainfall patterns will vary by region. Some areas may face more droughts or floods. Warmer climates will likely bring less snow and more rain. Changes in snowfall and melting will affect water availability in mountain regions.

Options for improvements

A review in 2006 said, "It is surprisingly hard to know whether water is truly scarce worldwide (a supply problem) or if it is available but not used properly (a demand problem)."

The United Nations' International Resource Panel says governments have spent a lot of money on large, inefficient projects such as dams, canals, aqueducts, pipelines, and water reservoirs. These projects are usually not good for the environment or cost-effective. The panel says the best way to reduce water use without slowing economic growth is for governments to create comprehensive water management plans. These plans would consider the full water cycle, including where water comes from, how it is used, treated, reused, and returned to the environment.

In general, there is enough water worldwide each year. The real issue is that water supply changes over time and in different areas. Reservoirs and pipelines can help manage uneven water supply. Well-planned infrastructure and managing how much water is used are both needed. Both ways of managing water have benefits and challenges.

Not working together can cause water conflicts, especially in developing countries. These conflicts often happen because of disagreements about how water is shared, used, or managed. For example, Egypt and Ethiopia had a disagreement about the Grand Ethiopian Renaissance Dam in 2020. Egypt believes the dam could greatly reduce the water it receives from the Nile.

Water conservation means managing fresh water in a way that protects the environment and meets people’s needs now and in the future. It includes all actions, plans, and strategies to avoid water shortages. Factors like population size, family size, growth, and wealth affect how much water is used.

The terms "water efficiency" and "water conservation" are sometimes used the same way, but they are different. Water efficiency means using technology to use water more wisely and reduce waste. Water conservation means taking actions to save or protect water. In short, water efficiency focuses on new tools and ideas to use water better, while water conservation is about saving water.

There are several man-made sources of fresh water. One is treated wastewater, also called reclaimed water. Another is water collected from the air using machines called atmospheric water generators. Desalinated seawater, which is saltwater turned into fresh water, is also an important source. It is important to think about the costs and effects on the environment of these methods.

Water reclamation is the process of cleaning wastewater from homes, businesses, or industries so it can be reused for many purposes. This is also called wastewater reuse or recycling. Water can be reused in cities, for farming, or to help the environment. It can also be used for drinking water, though this is rare. Reusing water for irrigation or to refill groundwater is common, especially in dry areas. Reused water can also be used in homes for tasks like flushing toilets or in industries.

Wastewater treatment is the process of cleaning wastewater so it is safe to return to the environment. Domestic wastewater, also called sewage, is cleaned at sewage treatment plants. Industrial wastewater is often cleaned at special plants or at sewage treatment plants after the company cleans it first. Other types of wastewater treatment include cleaning water from farms and treating waste from landfills.

The term "wastewater treatment" is often used to describe the process of cleaning sewage.

Desalination is a man-made process that removes salt and minerals from saltwater, usually seawater, to make fresh water. This process can produce water for drinking or farming, but it also creates salty waste as a byproduct.

The virtual water trade is the hidden movement of water through goods and services that are bought and sold between places. This is also called embedded or embodied water. This idea helps understand water problems from global, regional, and local perspectives. However, using virtual water estimates may not help leaders make decisions to protect the environment.

For example, cereal grains have been a major way water is moved through trade in places where water is scarce. Importing cereal can help countries with little water meet their needs. However, poor countries may not be able to afford these imports in the future, which could lead to not having enough food to eat.

Regional examples

The Consultative Group on International Agricultural Research (CGIAR) created a map showing which countries and regions have the most water stress. These areas include North Africa, the Middle East, India, Central Asia, China, Chile, Colombia, South Africa, Canada, and Australia. Water scarcity is also increasing in South Asia. By 2016, about four billion people, or two-thirds of the world’s population, were experiencing severe water shortages.

More developed countries in North America, Europe, and Russia are unlikely to face serious water supply problems by 2025. This is because they have more water resources that match their population size. However, regions like North Africa, the Middle East, South Africa, and northern China will face very serious water shortages. This is due to limited water supplies and large populations. Most of South America, Sub-Saharan Africa, southern China, and India will also face water shortages by 2025. For these areas, water scarcity is caused by economic challenges in providing safe drinking water and rapid population growth.

In Africa, the main causes of water scarcity are physical and economic water shortages, fast population growth, and changes in the water cycle caused by climate change. Water scarcity means not having enough fresh water to meet basic needs. Rainfall in sub-Saharan Africa is uneven and seasonal, leading to frequent floods and droughts.

In 2012, the Food and Agriculture Organization of the United Nations reported that water scarcity is now one of the biggest challenges for sustainable development. This is because many river basins have reached conditions of water scarcity due to high demand from agriculture and other industries. Water scarcity in Africa affects health, especially for women and children, education, farming, and long-term development. It can also lead to more conflicts over water.

In Yemen, water scarcity is growing. Causes include population growth, climate change, poor water management, changes in rainfall, aging water systems, weak governance, and human activities. By 2011, water shortages were already causing political, economic, and social problems in Yemen. By 2015, Yemen was among the countries most affected by water scarcity. Most people in Yemen experience water shortages for at least one month each year.

In Nigeria, rising temperatures, droughts, and the shrinking of Lake Chad are causing water shortages and forcing people to move. This migration is pushing thousands to nearby countries like Chad and towns.

A 2019 report by over 200 researchers found that Himalayan glaciers could lose 66% of their ice by 2100. These glaciers feed Asia’s largest rivers, including the Ganges, Indus, Brahmaputra, Yangtze, Mekong, Salween, and Yellow. Around 2.4 billion people live in areas where these rivers flow. Countries like India, China, Pakistan, Bangladesh, Nepal, and Myanmar may face floods followed by droughts in the coming decades. In India alone, the Ganges provides water for drinking and farming for over 500 million people.

Despite overusing groundwater, China is facing a grain shortage. This could raise grain prices worldwide. Most of the 3 billion people expected to be added to the global population by mid-century will live in countries already dealing with water shortages. If population growth continues without slowing, experts worry there may be no peaceful or humane way to address the global water shortage.

Climate change in Turkey is likely to make its southern river basins water-scarce before 2070, with increasing droughts.

In the Rio Grande Valley, large-scale farming has worsened water scarcity and caused disputes over water rights between Mexico and the United States. Experts like Armand Peschard-Sverdrup from Mexico say these conflicts require better international water management. Some compare the disputes to a battle over limited natural resources.

The western coast of North America relies heavily on water from glaciers in mountain ranges like the Rocky Mountains and Sierra Nevada. This region is also at risk due to climate change.

Most of Australia is desert or semi-arid land, known as the outback. Many areas and cities in Australia have water restrictions due to long-term droughts. Environmentalist Tim Flannery predicted that Perth in Western Australia could become the world’s first "ghost metropolis," a city abandoned due to lack of water. In 2010, Perth had its second-driest winter on record, and water restrictions were tightened.

Some countries have shown that using less water while growing their economies is possible. For example, Australia reduced water use by 40% between 2001 and 2009, even as its economy grew by over 30%.

Society and culture

Sustainable Development Goal 6 focuses on providing clean water and proper sanitation for everyone. It is one of 17 goals created by the United Nations General Assembly in 2015. The fourth target of SDG 6 is about water shortages. It states: "By 2030, significantly increase how efficiently water is used in all areas and ensure that fresh water is taken and provided in a way that helps with water shortages. This should greatly reduce the number of people who do not have enough water."