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.

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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