ABSTRACT
Water scarcity can be succinctly summarized by three easy-to-remember numbers: 1,700, 1,000 and 500 m3 per person per year. A region is experiencing water stress when annual natural water supplies available on a sustainable fashion drop below 1,700 m3. When natural annual water supplies drop below 1,000 m3, the population faces water scarcity, and below 500 m3 “absolute scarcity” (Falkenmark et al. 1989). Annual renewable water supplies, while fluctuating from year to year, are on average constant, with a possible long-term trend due to climate change. In contrast, population grows constantly in most regions. As a result, per capita water availability declines over time, turning more regions water stressed as time goes by. Table 14.1 (based on World Bank data) reports the population that live in water stressed, water scarce and absolute scarcity conditions in 2012 and 2050 (the latter is based on World Bank population predictions). The m3 per person per year figures refer to internal renewable resources (internal river flows and groundwater from rainfall) divided by the World Bank’s population estimates. Due to spatial and temporal variability, a more refined (e.g., regional and seasonal) data will reveal larger populations under water shortage conditions. 1 Worldwide water shortages https://www.niso.org/standards/z39-96/ns/oasis-exchange/table">
2011
2050
Water stress
(less than 1,700 m3 per person per year)
Population (million)
2,842.29
6,209.14
Number of countries
65
80
Water scarce
(less than 1,000 m3 per person per year)
Population (million)
905.56
51.63
Number of countries
43
28
Absolute scarcity
(less than 500 m3 per person per year)
Population (million)
5,595.66
2,956.83
Number of countries
65
57
Source: Adapted from Falkenmark et al. (1989).