Glaciers in the Himalayan mountain range are melting because of rising temperatures, bringing the threat of floods to communities in Bangladesh, Bhutan, India and Nepal. But scientists in Nepal say the extent of the threat is unknown because no systemic research has been done since the mid-1990s, and no early warning system is in place for villages downstream.

Between 1970 and 1989 most glaciers in Nepal's Khumbu region retreated by 10-60 metres as they melted. The lack of more recent data is a cause for concern. Nepal has 3,300 glaciers, two-thirds of which have glacier lakes that are growing in size as the ice melts. If the volume of water reaches a critical level, the lakes could burst, releasing water in flash floods that would threaten people, settlements and infrastructure in lower-lying areas across South Asia.

In the longer-term, the melting glaciers could result in water shortages throughout the region. Nearly 70 per cent of the water in the River Ganges comes from rivers in Nepal, which are fed by the country's glaciers. If the Himalayan glaciers disappear, rivers at lower altitudes will also dry up. Syed Iqbal Hosnain of the University of Calcutta, India, warns that the flow of some rivers could decrease by 90 per cent.

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