The number of people exposed to water stress in relation to how much water is reserved for the environment: a global modelling study
Background: Increasing human water use and changes in water availability due to global warming are great challenges for water security worldwide. Human exploitation of water resources induces stress in freshwater environments when ecosystem needs are not met, leading to biodiversity loss and reduced ecosystem services. Ecosystem water requirements are however unknown for most river basins around the world, which impacts our ability to correctly quantify human water stress.
Methods Here we assess monthly global water stress by combining fine-scale natural water availability and human water use data and consider three different ecosystem water requirements defined as environmental flow requirements. We compute the related amount of people under water stress worldwide and on a national level.
Findings We find that ensuring high ecological protection puts nearly half of the world’s population (3.2 billion people) under water stress for at least one month per year, and more than a quarter (1.9 billion) for at least six months per year. These amounts reduce to 2.2 billion respectively 1 billion when allocating only minimum flow requirements to the environment, but with potential effects on biodiversity. Around 80% of these people live in Asia, particularly in water stress hotspot regions in India, Pakistan and northeastern China.
Interpretation Our results demonstrate the important trade-off policy makers and water managers have to make when allocating limited water resources between direct human needs and the environment. Crucial to alleviating current and future human water stress while sustaining healthy ecosystems is to better understand local ecosystem needs.
VANHAM Davy;
ALFIERI Lorenzo;
FLOERKE Martina;
GRIMALDI Stefania;
LORINI Valerio;
DE ROO Arie;
FEYEN Luc;
2022-07-26
ELSEVIER SCI LTD
JRC121629
2542-5196 (online),
https://www.thelancet.com/journals/lanplh/article/PIIS2542-519600234-5/fulltext,
https://publications.jrc.ec.europa.eu/repository/handle/JRC121629,
10.1016/S2542-5196(21)00234-5 (online),
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