Global Water Stress: Physical vs Economic Scarcity

Water stress occurs when the demand for water exceeds the available supply or when poor quality limits its use; physical water scarcity means that there is not enough water to meet demand, while economic water scarcity means that water exists but people lack the money, infrastructure or institutions to get it. In brief: the Falkenmark indicator classifies a country as water-stressed when there is less than 1,700 m³ of renewable fresh water per person per year, as water-scarce below 1,000 m³ and as having absolute scarcity below 500 m³. Physical scarcity is typical of dry regions such as the Middle East and North Africa, and economic scarcity is common in parts of Sub-Saharan Africa.

Water shortages affect health, food production and stability, and they are expected to increase with population growth and climate change. This guide explains how water stress is measured, the difference between physical and economic scarcity, the main causes and solutions, compares the two types in a table, works through calculations, outlines the history and corrects common mistakes.

How is water stress measured?

The Swedish hydrologist Malin Falkenmark proposed in the 1980s a simple indicator of the renewable water available per person per year.

• More than 1,700 m³ per person: water supply is generally sufficient, with occasional or local problems.
• 1,000–1,700 m³: water stress.
• 500–1,000 m³: water scarcity.
• Less than 500 m³: absolute scarcity.

Another common indicator is the ratio of water withdrawn to available renewable water: a ratio above 25–40% is considered high stress. These national averages can hide local and seasonal shortages, quality problems and inequalities in access. Global estimates suggest that around 2 billion people live in countries with high water stress, and that about 4 billion people experience severe scarcity for at least one month a year. Agriculture accounts for roughly 70% of global freshwater withdrawals, industry for about 20% and households for about 10%. In addition, about 2 billion people lack access to safely managed drinking water at home.

What is physical water scarcity?

Physical scarcity occurs where the natural supply is too small for the demand, because of low rainfall, high evaporation or heavy use, and where more than about 75% of river flows are already withdrawn. It is found in the arid and semi-arid regions of the Middle East and North Africa, Central Asia, northwest India, northern China, the southwestern United States and parts of Australia and southern Europe. Symptoms include falling water tables, drying rivers and lakes (such as the Aral Sea and the lower Colorado River), and heavy use of fossil groundwater and desalination. Rapid population growth and irrigation in dry places, such as Saudi Arabia, have increased the problem. Some countries, such as Singapore and Israel, have responded with reuse, desalination and strict management.

What is economic water scarcity?

Economic scarcity occurs where water is available in rivers and aquifers but less than 25% of it is withdrawn, because of a lack of investment in infrastructure (wells, pipes, dams, treatment), weak institutions, poverty, conflict or poor management. It is typical of many parts of Sub-Saharan Africa, South Asia and Latin America. People may walk long distances to collect water, rely on vendors who charge high prices, or use unsafe sources, even in a region with plenty of rain. The solution here is not more water but better access: funding, technology and governance. Many places have both types of problem, and some have seasonal drought together with poor infrastructure.

What are the solutions?

• Efficiency in farming: drip irrigation, laser leveling, drought-tolerant crops and better scheduling.
• Reducing losses: repairing leaking pipes, which can lose a third or more of the water in poorly maintained systems, and using water meters and fair pricing.
• Reuse and recycling: treated wastewater for irrigation and industry, and for drinking in places such as Singapore (NEWater).
• Desalination: removing salt from seawater, used heavily in the Gulf states and Israel, but costly in energy and brine disposal.
• Rainwater harvesting and storage: tanks, small dams and recharge of aquifers.
• Water transfers and trade: moving water or “virtual water” embodied in food.
• Governance and investment: clear water rights, integrated river basin management, community-managed supplies and international finance for water and sanitation in poorer countries.

Physical and economic scarcity compared

Worked example: water per person and footprints

The values are hypothetical or approximate and illustrate the calculations.

1. Water per person: a country has 60 billion m³ of renewable water per year and 40 million people. The availability is 60,000,000,000 ÷ 40,000,000 = 1,500 m³ per person, which is in the “water stress” range (1,000–1,700).
2. Population growth: if the population grows to 65 million with the same water, the availability falls to 60,000,000,000 ÷ 65,000,000 = 923 m³ per person, which is in the “water scarcity” range (500–1,000).
3. Withdrawal ratio: the country withdraws 36 billion m³, which is 36 ÷ 60 = 60% of renewable water, a very high level of use (physical scarcity).
4. Economic scarcity: another country has 800 billion m³ and withdraws 30 billion, which is 30 ÷ 800 = 3.75%, a low share. If 40% of its people lack safe water, the problem is one of access and not supply.
5. Water footprint: producing 1 kg of beef takes on the order of 15,000 liters of water in total (mostly for feed), 1 kg of wheat about 1,800 liters and a cup of coffee about 140 liters. A diet that includes 100 g of beef a day (0.1 kg) has a water footprint from beef of 0.1 × 15,000 = 1,500 liters a day, or 1.5 m³.
6. Leakage: a city supplies 500,000 m³ a day and loses 30% through leaks. The loss is 150,000 m³ a day. Fixing a third of the leaks saves 50,000 m³ a day, enough for 50,000,000 ÷ 150 = 333,000 people at 150 liters per person per day.

How has the concept developed?

Water supply has been a concern since ancient irrigation civilizations. In the 1980s and 1990s, Falkenmark’s indicator gave a simple measure of stress. The 1992 Dublin Principles stated that water is an economic good as well as a social one. In 2007, the International Water Management Institute’s Comprehensive Assessment of Water Management in Agriculture introduced the map of physical and economic scarcity. The UN recognized the human right to water and sanitation in 2010, and the Sustainable Development Goals include SDG 6, which aims for clean water and sanitation for all by 2030. The idea of “virtual water,” proposed by Tony Allan in the 1990s, showed how countries import water through food. The first UN Water Conference for nearly 50 years was held in 2023.

Which mistakes are common?

Mistake 1: Assuming that water scarcity only happens in deserts

Wet regions can experience scarcity too, when infrastructure is lacking or quality is poor, or when demand is very high, as in densely populated river basins.

Mistake 2: Relying only on national averages

Averages hide differences between regions, seasons and income groups. A country may have enough water in total, but not where people live.

Mistake 3: Thinking that more water is always the solution

In economic scarcity, the problem is access and management. In physical scarcity, efficiency and demand management matter as much as new supply.

Mistake 4: Forgetting water embedded in goods

Food and products need large amounts of water, so consumption and trade shift the pressure on water between regions.