Water stress means that water demand exceeds the available supply during a given period, or that water is too polluted or saline to be usable, so human and ecological needs cannot be met adequately. It is a broader concept than simple “scarcity” because it combines availability, quality, and access to freshwater.
Water stress occurs when the ratio of water withdrawals to renewable water resources is high, indicating strong competition among users such as agriculture, industry, and households. Many agencies define areas as highly or extremely water‑stressed when a large share (around 40–80% or more) of renewable supply is withdrawn each year.
Key factors of water stress include population growth, the expansion of irrigated agriculture and industry, over-extraction of groundwater, and pollution that reduces usable water. Climate change adds pressure by altering rainfall patterns, increasing drought frequency, and reducing renewable water resources per degree of warming.
Sun and Water Drive Climate, Not Us
Persistent water stress leads to declining river flows, falling groundwater tables, and degradation of aquatic ecosystems, as well as higher treatment costs due to deteriorating water quality. It also threatens food and energy security, public health, and economic growth, especially where governance and infrastructure are weak.
Roughly half of the world’s population experiences highly water‑stressed conditions for at least one month each year, and about a quarter live in countries facing extremely high water stress. Regions such as the Middle East, North Africa, and large parts of South Asia are among the most affected and are projected to see stress intensify by mid‑century.
At the national scale, water stress is often assessed using per‑capita renewable water availability and withdrawal ratios, with thresholds marking stress, scarcity, and absolute scarcity. Tools such as Aqueduct Water Risk Atlas use these metrics to map current and future stress and to support planning and adaptation strategies
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