Working Group II: Impacts, Adaptation and Vulnerability


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11.2.3. Hydrology and Water Resources

11.2.3.1. Water Availability

One-third of the world's renewable water resources (13,500 km3 yr-1 out of 42,700 km3 yr-1) are concentrated in Asia (Shiklomanov, 2001). Water availability varies widely across the different regions of Asia, however—from 77,000 m3 yr-1 per capita to less than 1,000 m3 yr-1 per capita. Table 11-7 provides available information on renewable local water resources, water availability, and water use dynamics by natural-economic region of Asia. The major share of Asian water resources (72%) is located in four countries: Russia (3,107 km3 yr-1), China (2,700 km3 yr-1), Indonesia (2,530 km3 yr-1), and India (1,456 km3 yr-1). Water resources of the two largest river systems of Asia—the Ganges (with Brahmaputra and Meghna) and the Yangtze (Changjiang)—attain 1,389 km3 yr-1 (794 x 103 m3 yr-1 km-2) and 1,003 km3 yr-1 (554 x 103 m3 yr-1 km-2). Figure 11-11 depicts the spatial distribution of currently estimated annual mean surface runoff over Asia. The runoff distribution within a year in Asia is most uniform in the rivers of southeast Asia. Over the rest of the continent, more than half of the annual runoff is discharged during the three summer months.

Figure 11-11: Spatial distribution of currently estimated surface runoff (mm) over Asian continent (Shiklomanov, 2001).

Water availability—in terms of temporal as well as spatial distribution—is expected to be highly vulnerable to anticipated climate change. Growing populations and concentration of population in urban areas will exert increasing pressures on water availability and water quality. As reported in IPCC (1998), runoff generally is expected to increase in the high latitudes and near the equator and decrease in the mid-latitudes under anticipated climate change scenarios.

Table 11-7: Renewable local water resources, water availability, and water-use dynamics, by natural-economic regions of Asia (Shiklomanov, 2001).
Region Area
(106 km2)
Water Resources
(km3 yr-1)
Potential Water Availability
(103 m3 yr-1)
Dynamics of Freshwater Use (km3 yr-1)a Water Use as a Percentage of Water Resourcesa
      Forecast
per km2 per capita 1900 1950 1995 2000 2010 2025 1995 2025
Siberia and far east of Russia 12.76 3107 243 76.6 0.7 5.6 30.6 30 32 38 1.0 1.2
          0.4 1.3 15 15 17 21 0.5 0.6
                         
North China and Mongolia 8.29 1029 124 2.13 37 98 254 273 305 373 24.7 36.2
          30 75 182 182 194 210 17.7 20.4
                         
South Asia 4.49 1988 443 1.77 201 367 932 969 1060 1370 43.6 64.1
          160 293 687 710 767 944 32.1 44.2
                         
Southeast Asia 6.95 6646 956 4.77 99 230 525 551 617 781 7.8 11.6
          77 170 388 393 413 425 5.8 6.3
                         
Western Asia 6.82 490 71.8 2.11 43 91 238 248 283 346 48.5 70.6
          34 71 174 181 201 229 35.5 46.7
                         
Central Asia and Kazakhstan 3.99 181 45.4 3.78 29 57 154 151 160 169 75.5 82.8
          19 37 102 102 110 122 50.0 59.8
                         
Transcaucasia 0.19 67.9 358 4.63 4.2 11.4 23.7 23 26 27 32.0 36.5
          2.1 7.1 17.5 17 19 20 23.7 27.0
Total 43.50 13510 311 3.92 414 860 2157 2245 2483 3104 16.0 23.0
          322 654 1565 1603 1721 1971 11.6 14.6
a Nominator = total water withdrawal; denominator = water consumption.

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