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News article1 December 2021

Water stress – a delicate balance between humans and the environment

Increasing water demand puts people and environment under water stress.
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A new paper in The Lancet Planetary Health finds that an extra 1 billion people experience water stress at least 1 month per year under high (3.2 billion) compared to low (2.2 billion) environmental flow protection regimes.

This is the first study to quantify the global and national numbers of people to experience periods of water stress under different ecosystem protection (environmental flow) measures.

Allocating water resources for human and environmental uses

Water is essential for human water use (drinking water, industry, agriculture, energy) and to sustain healthy ecosystems. Where there is not enough water in a given location for both uses, people and the environment may face water stress.

Environmental flows are water flows that need to remain in a stream or river to maintain biodiversity and ecosystems. Aquatic biodiversity is in serious need of protection, especially given that the number of globally monitored freshwater species has declined by 84% between 1970 and 2016. Aquatic biodiversity includes not only freshwater fish, but also amphibians, water birds and mammals such as beavers, otters, hippos, crocodiles and freshwater dolphins.

Yet environmental flows remain unknown for most river basins in the world.

Human exposure to water stress

The Lancet study finds that, depending on the level of environmental flow protection, 2.2 billion to 3.2 billion people experience water stress for at least 1 month per year (corresponding to 32% and 46% of the world's population, respectively). Around 80% of people living under water stress live in Asia, notably in India, Pakistan, and northeast China.

In the EU, an estimated 45 to 102 million people live under water stress for at least one month per year under low and high environmental flow protection measures, respectively. Most of these people live in the Mediterranean region, although many can also be found in countries such as Germany or Belgium.

Environmental flows

Environmental flows sustain ecosystems and the services they provide, which are essential for human livelihoods and wellbeing. Such ecosystem services include providing freshwater fish for nutrition and sustaining wetlands, which provide natural flood protection, store carbon and reduce water pollution by filtering nutrients.

According to the lead author, Davy Vanham, “Balancing water allocation between direct human use and environmental flows is not straightforward. Take the lower Mekong basin, where freshwater fish accounts for more than 50% of protein from animal sources in local diets. Putting both rice and fish on the table requires water for agriculture (rice) and healthy environmental flows (fish).”

Supporting the Sustainable Development Goals and policy development

The study uses Sustainable Development Goal (SDG) indicator 6.4.2 on water stress, one of two indicators used to measure progress towards SDG target 6.4, which aims to reduce the number of people facing water stress by 2030.

A better understanding of local ecosystem needs is crucial to alleviating current and future human water stress, while sustaining healthy ecosystems and their services.

Further information

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EU Biodiversity Strategy for 2030 - Bringing nature back into our lives


Publication date
1 December 2021