State and Trends
withdrawals, municipalities for 9 per cent and industry for 9 per cent (Frenken 2012). Industry’s share of water use is high in China (23.2 per cent). In Australia, Japan and New Zealand the agriculture share ranges from 62–67 per cent, municipalities from 15–21 per cent, and industry from 13–23 per cent (FAO 2015e). Water productivity – GDP in 2005 constant prices divided by annual total water withdrawals – varies widely in the region, with developed countries such as Japan having high water productivity of USD53 per cubic metre compared to USD2 per cubic metre for countries in South Asia other than the Maldives (World Bank 2013).
Climate change impact on water resources is particularly pronounced in Asia since rivers originating in the Hindu Kush Himalayas are among the world’s most melt-water- dependent systems. This region, extending over 3 500 kilometres, is the source of ten large Asian river systems – the Amu Darya, Brahmaputra (Yarlungtsanpo), Ganges, Indus, Irrawaddy, Mekong (Lancang), Salween (Nu), Tarim (Dayan), Yangtse (Jinsha) and Yellow River (Huanghe) – and provides water for 1.3 billion people, 20 per cent of the world’s population. The Brahmaputra, Ganges and Indus river basins alone support around 700 million people (Eriksson et al. 2009) with around 144 900 hectares in the Indus basin irrigated, 156 300 hectares in the Ganges basin, and 6 000 hectares in the Brahmaputra basin (Immerzeel et al. 2010). Water security is aggravated by factors such as increased flooding due to Himalayan glacier melting, decreased river flows due to reduced snow cover, changes in rainfall and rainfall patterns, and higher rates of chemical reactions in water bodies due to warming.
2.4.3 Pressures
The increased water demand for agricultural, domestic and industrial use has led to overexploitation. The resulting increased scarcity of water and decreased water security compromises water availability for human wellbeing and economic development. Moreover, water-dependent ecosystems, such as wetlands, can be pushed beyond their tipping points, leading to irreversible environmental impacts.
As a result of the large population and growing regional economy, pollution of surface and ground water sources is rampant due to the release of untreated sewage, agricultural run-off, industrial effluents, and leaching from waste landfills. Salinization of fresh water sources in coastal areas due to incursion of seawater is aggravated by rising sea level. The Water Quality Index, based on dissolved oxygen, acidity, conductivity, total nitrogen and total phosphorous, shows a large variation in the region (Esty et al. 2008). Against a target value of 100, the values are in the range of 34.0–99.4, with New Zealand having the best water quality.
2.4.4 State and trends
Table 2.4.1 summarizes water-related issues in the region such as susceptibility to floods, cyclones and drought, elevated ecosystem/climate change risk and poor access to sanitation.
Water quantity
Mapping the total renewable water resources per person – cubic metres per person per year – in 2014 indicates low water availability in Northeast and South Asia (Figure 2.4.1). Baseline water stress – the ratio of total annual water withdrawals to total available annual renewable supply – indicates moderate to high stress (rating 3–5) in Afghanistan, Australia, India, Japan, Republic of Korea, Mongolia, Pakistan, Philippines and Singapore (WRI 2013). Monthly consumptive use of ground and surface water flows indicates heavily populated river basins – Tarim and Yongding He in China and the Cauvery, Indus and Penner in India – face severe water scarcity for 8–12 months per year (Hoekstra et al. 2012).
Climate change, rising temperatures and changes in precipitation cause enhanced evapotranspiration, variations in seasonal extremes and in glacier volume (Bolch et al. 2012) and changes in snow and glacier melt (Lutz et al. 2014), all of which alter the hydrological regime of Hindu Kush Himalayas river systems. Glacier melting has also occurred in New Zealand (UNEP 2008) and China (Ives 2012). In 1978,
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