This could have devastating consequences for millions of people in the plains of the Indus, Ganges and Brahmaputra rivers, which are recharged by snow and ice melt-water from the glacier- covered area.
Scientists from China, Russia and Japan will be presenting their findings on the phenomenon during a two-day meeting of the International Commission on Snow and Ice in Birmingham next week.
Gordon Young, secretary- general of the International Association of Hydrological Sciences, who has studied glaciers in the Himalayas for more than 20 years, says it is the "general trend" that the world's glaciers are getting smaller. "Glaciers are reservoirs of water and as they melt due to climate warming and get smaller, those reservoirs get smaller," he says.
"And in the Himalayas they are giving water to a population which is twice that of North America. That's about 500 million people."
Professor Young, who teaches at the Wilfrid Laurier University in Canada, says there is a risk of some rivers running dry in the summer. Until now, the melted water running from the glaciers has helped to compensate for the lack of rain.
"Glaciers tend to melt out in the summer and that is the time when a great deal of water is needed for agriculture. So it's precisely at the time when water is most needed those glaciers give their water. And the threat is that in the future there won't be that water to use."
At present, the melting glaciers form huge lakes, which present flood threats to millions of people living in the nearby valleys. In August 1985 hundreds of people died in the Khumbal Himal region of Nepal when the fragile wall of ice and debris surrounding a glacier gave way, releasing a wall of water 15 yards high. Score of houses were washed away and a hydro-electric plant was wrecked in the catastrophe.
Surveys reveal that glaciers such as the Gangotri, which feeds the Ganges, has lost one-third of its 15-mile length in the past 50 years.
Professor Young says the melting of the glaciers in the Himalayas is not an isolated phenomenon but part of a global trend. The Alps have lost about 50 per cent of their ice in the past century, and half of the 27 glaciers that existed in Spain in 1980 have disappeared.
The largest glacier on Mount Kenya has shrunk by about one-tenth in the past 100 years and those on Mount Kilimanjaro, also in Kenya, are only a quarter as big.