<P> Owing to the mountains' latitude near the Tropic of Cancer, the permanent snow line is among the highest in the world at typically around 5,500 metres (18,000 ft). In contrast, equatorial mountains in New Guinea, the Rwenzoris and Colombia have a snow line some 900 metres (2,950 ft) lower . The higher regions of the Himalayas are snowbound throughout the year, in spite of their proximity to the tropics, and they form the sources of several large perennial rivers . </P> <P> In recent years, scientists have monitored a notable increase in the rate of glacier retreat across the region as a result of global climate change . For example, glacial lakes have been forming rapidly on the surface of debris - covered glaciers in the Bhutan Himalaya during the last few decades . Although the effect of this will not be known for many years, it potentially could mean disaster for the hundreds of millions of people who rely on the glaciers to feed the rivers during the dry seasons . </P> <P> The Himalayan region is dotted with hundreds of lakes . Most lakes are found at altitudes of less than 5,000 m, with the size of the lakes diminishing with altitude . Tilicho Lake in Nepal in the Annapurna massif is one of the highest lakes in the world . Pangong Tso, which is spread across the border between India and China, and Yamdrok Tso, located in central Tibet, are amongst the largest with surface areas of 700 km2, and 638 km2, respectively . Other notable lakes include She - Phoksundo Lake in the Shey Phoksundo National Park of Nepal, Gurudongmar Lake, in North Sikkim, Gokyo Lakes in Solukhumbu district of Nepal and Lake Tsongmo, near the Indo - China border in Sikkim . </P> <P> Some of the lakes present a danger of a glacial lake outburst flood . The Tsho Rolpa glacier lake in the Rowaling Valley, in the Dolakha District of Nepal, is rated as the most dangerous . The lake, which is located at an altitude of 4,580 metres (15,030 ft) has grown considerably over the last 50 years due to glacial melting . </P>

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