5.7 - Water stress, scarcity and rising demand
Learn to distinguish water-stress indicators, explain physical and human pressures on usable supply, and interpret global patterns and future demand without concealing local inequality.
Measuring supply per person
Water insecurity occurs when people or ecosystems cannot reliably obtain enough suitable water. A country may have plentiful annual freshwater but unsafe household supplies; another may have little natural freshwater yet provide reliable treated water. An indicator measures one aspect of that wider problem.
Water stress and water scarcity
Using the specification's annual renewable freshwater-per-person thresholds, water stress begins below per person per year and water scarcity below per person per year. Below 1,000 is also within the stressed range; the categories are nested thresholds.
Annual freshwater availability per person . Use cubic metres and a common year/boundary.
An original illustrative country has of renewable freshwater annually and 8 million people. Since , availability is per person per year: stressed but above the scarcity threshold. If population rises to 15 million with supply unchanged, the value becomes 800: below the scarcity threshold. This is arithmetic under stated assumptions, not a forecast of that country.
A national annual mean conceals seasonal drought, water quality, regional concentration and access. Renewable freshwater is not all economically accessible, nor can all of it be abstracted without ecological damage. Transfers and desalination may improve supply but are not an increase in naturally renewable river water. Do not infer equal household allocations from a per-person ratio.
Mapping global stress
A global map reveals regional concentrations and exceptions, but the legend determines what its colours mean. The WRI Aqueduct 4.0 global water-risk map uses a different stress measure from the per-person thresholds: demand relative to available renewable supply. Its 2023 assessment identifies extremely high stress where at least 80% of renewable supply is withdrawn, with major concentrations in the Middle East and North Africa and South Asia. WRI's 2023 findings and map.
To analyse the map, first select baseline water stress rather than another layer such as drought risk. State the measure and baseline, read the colour categories, locate clusters, and then zoom into contrasting basins. Compare the arid Arabian Peninsula with monsoonal South Asia: low renewable supply helps explain the former, while concentrated irrigation, population and seasonal demand help explain stress in the latter despite wetter periods. Humid areas with lower stress are useful contrasts, but rainfall alone does not establish accessible household supply.
Look for within-country variation rather than assign one colour to every resident. Basin boundaries follow water systems; country boundaries follow political units. A country's aggregate can conceal both a stressed irrigated basin and a wetter sparsely populated region. A map with blank cells may show missing data, not an absence of risk. Future layers are modelled scenario outputs, not measurements from the future.
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