Braun, Ludwig; Hagg, Wilfried
Present and future impact of snow cover and glaciers on runoff from mountain regions. comparison between Alps and Tien Shan.
In: IHP-HWRP-Berichte, Vol. 8: pp. 36-43
The aim of this contribution is to show how snow- and glaciermelt influence runoff today and in the future under the assumption that global warming continues. This assumption will not necessarily come into effect, but according to climatologists, the opposite is rather unlikely in the next few hundred years, for example a drastic cooling due to changes in ocean currents. Mountain regions receive more precipitation than the lowlands around them, and act as a reservoir of this excess water by temporarily storing it in the form of snow and ice.
Melt is highest during warm and dry periods and thus runoff increases during times of drought. This release from snow and ice storage ensures a reliable water flow in rivers, and thus is of great value in terms of irrigation and other water uses. Glaciers, therefore, influence the water cycle very favourably by collecting water during times of abundance and releasing it when there is a lack of precipitation.
Even in a warmer climate we expect precipitation to fall abundantly in the mountains, but more and more in the form of rain rather than snow, and therefore the character of runoff will change from a glacial or nival regime towards a pluvial one. This will produce a less reliable water yield and the absence of glaciers will lead to water shortages during hot and dry summers, when water is needed most urgently for irrigation and drinking water. Therefore, we need to develop strategies to adapt to the situation that rivers will run dry more often in the future.