The Great Melt & the Great Thirst

This, the model says, is because the melting glaciers would increase the volume of water entering the rivers. But the writing on the wall is clear: increased flow means the glacier is depleting and slowly dying, drying up the very source of the river.

This model and its findings will be discussed during a two-day workshop beginning here tomorrow. This comes amid speculation that Himalayan glaciers will disappear over the next 40 years.

Until recently, satellite data had shown the glaciers had decreased by 10 per cent in the Western Himalayas and 30 per cent in Eastern Himalayas.

In March 2002, UK’s Department of International Development (DFID) commissioned a project called SAGARMATHA (Snow and Galcier Aspects of Water Resources Management in the Himalayas) to assess the impact of deglaciation on the seasonal and long-term water resources in snow-fed Himalayan rivers.

The results were obtained keeping four climate change scenarios with increasing and decreasing temperature and precipitation.

‘‘This information will be vital for policy-makers and specially those working on inter-linking of rivers as the flows available in rivers are likely to change dramatically over decades depending on the region,’’ said S I Hasnain, Vice Chancellor, University of Calicut and who was earlier spearheading the glacier studies programme at Jawaharlal Nehru University.

After sporadic efforts, this marks the first regional effort involving, India, Nepal, Pakistan, Bangladesh and Bhutan. Some of the institutes involved are University of Salford, Manchester, University of Wallingford, UK and ICIMOD, Kathmandu, Nepal.

These are some of the key findings:

• In the Upper Indus, the study sites show initial increases of 14 and 90 per cent in mean flows over the next few decades which will be followed by decreasing flows by 30 and 90 per cent of baseline in the subsequent decades of the 100-year scenario.

• For Ganges, the the response of the river near the glacier in Uttarkashi is different from downstream Allahabad. At Uttarkashi, flows peak at between 20 and 33 per cent baseline within the first two decades and then recede to 50 per cent of base line after 50 years.

• Near the Brahmaputra source, there is general decrease in decadal mean flows for all temperature scenarios as glaciers are few in the area and flows recede as the permanent snow cover reduces with increasing temperature.

• The catchment in the East Himalayas, which benefit from high precipitation of the summer monsoon every year, are less vulnerable to impacts of deglaciation than those in the West, where the monsoon is weaker.

The model recognises the role of precipitation as seen in the Brahmaputra basin: a thick covering of snow resulting from a strong monsoon insulates the glacier delay melt, a weak monsoon would expose a glacier to melting earlier and for longer.