🎯 Context

In water.2.1 you separated physical from economic water scarcity and met four ways to increase supply, including the Grand Ethiopian Renaissance Dam and desalination in the United Arab Emirates. In the last lesson you measured freshwater use from the whole planet down to a local stream, and saw how water is governed, from drought orders in the Pays de Gex to the agreement on the Genevese aquifer.

This lesson introduces a second measure of limited water, water stress. You will find out why a society can have plenty of water and still be stressed, why stress is rising for different reasons in different places, how a dispute over a shared river adds to it, which large-scale strategies can supply more water, what they cost the environment, and who is left without safe water.

By the end of the lesson you should be able to:

• distinguish between water stress and water scarcity, and apply the 1,700 m³ threshold to real data
• explain why Egypt falls below the water-stress threshold
• compare the causes of rising water stress in an emerging economy and a low-income country
• explain how the dispute over the Grand Ethiopian Renaissance Dam affects water stress, using its historical and political context
• evaluate industrial strategies for supplying water, and their environmental impacts
• use statistics to show how unequal access to safe drinking water affects First Nations in Canada

Phase 1: Scarce or stressed?

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4.2.13 “Water stress” like “water scarcity” is another measure of the limitation of water supply; it not only takes into account the scarcity of availability but also the water quality, environmental flows and accessibility.

A region may have an ample supply and not be suffering from water scarcity, but it may be experiencing water stress because of low water quality.

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4.2.14 Water stress is defined as a clean, accessible water supply of less than 1,700 cubic metres per year per capita.

Consider one example of a society that falls below this level and the reasons that account for this.

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Two measures of limited water

In water.2.1 you learned that water scarcity means limited availability: either there is not enough water in an area (physical scarcity), or a society cannot store and move the water it has (economic scarcity).

Water stress is a wider measure. It still counts how much water is available, but it also counts three more things:

• water quality: polluted or contaminated water cannot be used safely, however much of it there is
• environmental flows: the water that must be left in rivers, lakes and wetlands to keep their ecosystems working. You met the idea in the last lesson, when France asked Switzerland for a guaranteed minimum flow in the Rhône.
• accessibility: whether people can reach the water and afford it

So a region can have plenty of water and not suffer from scarcity, yet still be water-stressed because its water is polluted.

The IB puts a number on it. A society is water-stressed when its clean, accessible water supply is less than 1,700 m³ per person per year.

Other organisations measure water stress in other ways. The World Resources Institute, for example, uses the share of a region's available water that is withdrawn each year. In this course, use the IB definition.

1. Distinguish between water scarcity and water stress.

How much water per person?

The table gives each country's total renewable water resources, the water replenished each year by rain and by rivers flowing in from other countries, and its population.

To find the water available per person, divide the total water (billion m³) by the population (million) and multiply by 1,000. For example, a country with 10 billion m³ and 5 million people has 10 ÷ 5 × 1,000 = 2,000 m³ per person per year.

2. Complete the last two columns of the table. Round to the nearest whole number.

Sources: total renewable water resources from FAO AQUASTAT, 2017 estimates, as published in the CIA World Factbook; population from the World Bank (2022).