Story highlights Himalayan glaciers have been losing almost half a meter of ice each year since the start of this century

Scientists say mass melting could threaten water supplies for hundreds of millions of people in Asia

(CNN) Climate change is eating away Himalayan glaciers at a dramatic rate, a new study has revealed.

Spanning 2,000 kilometers and harboring some 600 billion tons of ice, Himalayan glaciers supply around 800 million people with water for irrigation, hydropower and drinking.

But they have been losing almost half a meter of ice each year since the start of this century -- double the amount of melting that occurred between 1975 and 2000 -- according to the Columbia University researchers behind the study.

Recently, the glaciers have lost around 8 billion tons of water a year -- the equivalent of 3.2 million Olympic-size swimming pools, say the researchers. And that could potentially threaten water supplies for hundreds of millions of people across parts of Asia.

As the ice melts it forms large glacial lakes, which are already impacting local communities, according to lead author Joshua Maurer.