GEO-6 Regional Assessment for Asia and the Pacific


New Zealand had glaciers covering around 1 160 square kilometres, with an ice volume of around 53 cubic kilometres. Between 1977 and 2005 an 11 per cent decrease in ice volume was reported (UNEP 2008). In China, rivers such as Tarim are affected due to melting of glaciers in the mountains of Tian, Kunlun, Karakoram, and the eastern Pamir (Ives 2012).


Rivers are also affected by dams and reservoirs that cause fragmentation that affects their flow and connectivity. A study on the impact of fragmentation on large river systems has found many in Asia and the Pacific to be moderately or strongly affected (Nilsson et al. 2005). The strongly affected rivers include Chang Jiang and Haihe in China.


Irrigated agriculture is a key sector, accounting for up to 90 per cent of consumptive water use. The largest areas under groundwater irrigation are in India, 39 million hectares, and China, 19 million hectares, (Siebert et al. 2010) leading to overexploitation of groundwater sources. Nearly half of the world’s total groundwater use is by Bangladesh, China, India, Nepal and Pakistan (IGRAC 2010), with groundwater levels having fallen in northern India, Pakistan and northern China (ADB 2013b). The groundwater recharge is further affected by deforestation, expanding agriculture and urban growth leading to rapid runoff that does not provide sufficient time for infiltration. A recent study has examined the world’s 37 largest aquifers, including seven in Asia and the Pacific, and determined the renewable groundwater stress calculated as the ratio between groundwater use and groundwater availability (Richey et al. 2015). Of the seven aquifers studied in the region, five are overstressed or variably stressed and two are unstressed.


Water quality


The common pollutants in the region are organics, nutrients (nitrogen and phosphorous), dissolved salts, heavy metals, pesticides and chemicals from industrial activities. The sources are untreated or partially treated sewage, agricultural runoff, industrial wastewater and landfill leachate, and nutrient and sediments washed from degraded land by heavy rainfall. Several river basins – the


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Ganges, Haihe, Huaihe, Indus and Yellow river basins, and some river stretches in southern India – have high organic pollution (UNEP 2015). This can be further aggravated by other pollution such as increased salinity as seen in the Ganges and Indus river basins.


A major cause of water pollution is poor sanitation, including defecation in the open, leading to contamination of surface and groundwater sources by organics, nutrients and bacterial coliform. Globally, the percentage of population using improved sanitation facilities was 68 per cent in 2015 (UNDP 2015), while in Asia and the Pacific it ranged from 29 per cent in the Solomon Islands, to 100 per cent in, among others, Australia, Japan, Republic of Korea and Singapore in 2012 (World Bank 2012). In 2015, sanitation coverage was below 50 per cent in South Asia (Afghanistan, India and Nepal), Southeast Asia (Cambodia and Timor-Leste) and Pacific (Kiribati, Papua New Guinea and Solomon Islands) (UN MDG database). Only 30 per cent of the wastewater generated in urban India is treated (CPCB 2012) while the coverage in Japan is 100 per cent (Ueda and Benouahi 2009). Untreated sewage emanating from sewer leaks leads to high nitrate levels in urban groundwater, as observed in Bangkok, Jakarta and Metro Manila (Umezawa et al. 2009). Microbial pollution from human and livestock sewage, in addition to being localised, also spreads to rivers and coastal areas as observed in bays of Pacific islands, and the Java Sea coastal areas; it has also affected aquaculture in Bay of Bengal and South China Sea (UNEP 2006).


Eutrophication, the excess growth of algae, is caused by high loading of nutrients – nitrogen and phosphorous – in water bodies resulting in reduced water quality, oxygen depletion and growth of harmful algal blooms (Figure 2.4.2). The sources of nutrients are urea in fertilizers and in the manufacture of various plastics and chemicals, untreated sewage, agricultural runoff, and atmospheric wet and dry deposition of nutrients during smoke haze events (Sundarambal et al. 2010). In attempts to enhance food production, over-application of chemical fertilizers is a common practice in China, India, Philippines and Thailand, leading to high nutrient overloads (Novotny et al.


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