Environment

Winter snowpack decline may cut water supplies

A decline in winter snowpacks in many mountainous regions of the world may soon lead to a reduction in many nations' water supplies, according to a new study.

Water from snow-dependent drainage basins in the Northern Hemisphere currently serving over two billion people run the risk of being critically imperilled in the coming years as winter snowpacks decline due to a changing climate.

In the Northern hemisphere, the maximum area usually covered by winter snow is about 45.2 million square kilometres (486,528,751 sq. ft.). In the U.S., snow melt from drainage basins in large parts of the west provides the major source of water for about 75 percent of the population. This is also true of drainage basins in southern Europe, the Mideast and central Asia.

As we have seen in the American west and in western Canada, winter snow pack is an important seasonal water source, not only for drinking water, but for farms, cities and ecosystems. Snow falling in the higher elevations of large mountain systems around the world gradually melts and the water runs into the lowlands during the spring and summer seasons.

This is when water is most needed by all of humankind, for drinking, storage, agriculture and our fragile ecosystems. But the study suggests that global warming is turning this system on its head, upsetting the balance. Studies are showing that winter precipitation is falling as rain, not snow in many parts of the world, and washing away, while snow that does fall is settling at higher elevations, yet melting earlier.

With a warming world, scientists have been studying declining snowpacks in a number of regions across the world, from the disappearing snowfields in the Rocky Mountains from Colorado to northern Montana, as well as in the Himalayas and other areas.

The basins most sensitive to change and having the most at stake for humans are: "The basins of northern and central California, where much of U.S. produce is grown; the basins of the Colorado and Rio Grande rivers, which serve much of the American West and northern Mexico; the Atlas basin of Morocco; the Ebro-Duero basin, which feeds water to Portugal and much of Spain and southern France; and a series of basins covering eastern Italy, the southern Balkans, several Caucasus nations, and northern Turkey."