With the retreat of glaciers in the Himalayas, a number of glacial lakes have been created. A growing concern is the potential for GLOFs researchers estimate 21 glacial lakes in Nepal and 24 in Bhutan pose hazards to human populations should their terminal moraines fail. One glacial lake identified as potentially hazardous is Bhutan's Raphstreng Tsho, which measured long, wide and deep in 1986. By 1995 the lake had swollen to a length of , in width and a depth of . In 1994 a GLOF from Luggye Tsho, a glacial lake adjacent to Raphstreng Tsho, killed 23 people downstream.