10.2.4.2 Hydrology and water resources
Rapid thawing of permafrost (Table 10.4) and decrease in depths of frozen soils (4 to 5 m in Tibet according to Wang et al., 2004b) due largely to rising temperature has threatened many cities and human settlements, has caused more frequent landslides and degeneration of some forest ecosystems, and has resulted in increased lake-water levels in the permafrost region of Asia (Osterkamp et al., 2000; Guo et al., 2001; Izrael and Anokhin, 2001; Jorgenson et al., 2001; Izrael et al., 2002b; Fedorov and Konstantinov, 2003; Gavriliev and Efremov, 2003; Melnikov and Revson, 2003; Nelson, 2003; ACIA, 2005).
Table 10.4. Recent trends in permafrost temperatures measured at different locations (modified from Romanovsky et al., 2002 and Izrael et al., 2006)
|Country ||Region ||Permafrost temperature change/trends ||References |
|Russia ||East Siberia (1.6 to 3.2 m), 1960 to 1992 ||+0.03°C/year ||Romanovsky et al., 2001 |
| ||West Siberia (10 m), 1960 to 2005 ||+0.6°C/year ||Izrael et al., 2006 |
|China ||Qinghai-Tibet Plateau (1975 to 1989) ||+0.2 to +0.3°C ||Cheng and Wu, 2007 |
|Kazakhstan ||Northern Tian Shan (1973 to 2003) ||+0.2° to +0.6°C ||Marchenko, 2002 |
|Mongolia ||Khentei and Khangai Mountains, Lake Hovsgol (1973 to 2003) ||+0.3° to +0.6°C || Sharkhuu, 2003 |
In drier parts of Asia, melting glaciers account for over 10% of freshwater supplies (Meshcherskaya and Blazhevich, 1990; Fitzharris, 1996; Meier, 1998). Glaciers in Asia are melting faster in recent years than before, as reported in Central Asia, Western Mongolia and North-West China, particularly the Zerafshan glacier, the Abramov glacier and the glaciers on the Tibetan Plateau (see Section 10.6.2) (Pu et al., 2004). As a result of rapid melting of glaciers, glacial runoff and frequency of glacial lake outbursts causing mudflows and avalanches have increased (Bhadra, 2002; WWF, 2005). A recent study in northern Pakistan, however, suggests that glaciers in the Indus Valley region may be expanding, due to increases in winter precipitation over western Himalayas during the past 40 years (Archer and Fowler, 2004).
In parts of China, the rise in temperature and decreases in precipitation (Ma and Fu, 2003; Wang and Zhai, 2003), along with increasing water use have caused water shortages that led to drying up of lakes and rivers ( Liu et al., 2006; Wang and Jin, 2006). In India, Pakistan, Nepal and Bangladesh, water shortages have been attributed to rapid urbanisation and industrialisation, population growth and inefficient water use, which are aggravated by changing climate and its adverse impacts on demand, supply and water quality. In arid Central and West Asia, changes in climate and its variability continue to challenge the ability of countries in the arid and semi-arid region to meet the growing demands for water (Abu-Taleb, 2000; UNEP, 2002; Bou-Zeid and El-Fadel, 2002; Ragab and Prudhomme, 2002). Decreasing precipitation and increasing temperature commonly associated with ENSO have been reported to increase water shortage, particularly in parts of Asia where water resources are already under stress from growing water demands and inefficiencies in water use (Manton et al., 2001).