Read here. The IPCC claims that modern "unprecedented" global warming has caused glaciers and snowpack to shrink, and mountainous areas to become more arid, thus diminishing/eliminating essential alpine river discharges. Whether it's the Himalayas or other mountainous regions though, the empirical evidence does not support the claims of modern warming being "unprecedented," nor the convenient disappearing of the Medieval Warming and Little Ice Age climates of Mann's 'hockey-stick.'
A new peer-reviewed study by Wolfe et al. found that a Canadian lake's modern water level, which is fed from Rocky Mountain water runoff, is significantly higher than during the Medieval Warming Period and higher than lake levels prior to the extended Medieval span. This is an unequivocal indicator that modern warming is not "unprecedented." (click on image to enlarge)
"A peer-reviewed paper published online today in the journal Geophysical Research Letters shows that drought of Western North America was considerably worse during the Medieval Warming Period than at the end of the 20th century. The paper also shows much more variation and extremes in the drought record over the past 5200 years than since the advent of industrialization and rising CO2 levels in the latter 20th century. The proxy records clearly show no correlation of drought with the claimed steady CO2 levels...""a new 5200-year record of Lake Athabasca water-level variations, which serves as a sensitive gauge of past changes in alpine-sourced river discharge, reveals that western Canadian society has developed during a rare period of unusually abundant water ‘subsidized’ by prior glacier expansion."" [Brent B. Wolfe, Thomas W. D. Edwards, Roland I. Hall, John W. Johnston 2011: Geophysical Research Letters]