Source of water for West at risk

The West's natural water-delivery system is breaking down under the strain of rising temperatures, upsetting a fragile truce between people and the dry land they inhabit.

Mountain-snow runoff already bears the scars of climate change in the highest elevations, where winter now arrives later and ends earlier. There, snow melts before downstream users need it, or vanishes in the mild-spring winds.

Scientists say this seasonal shift will deepen as temperatures rise. The change threatens not only the water but also the way it is stored and released in a delicate relay from storm clouds to mountains to streams and reservoirs.

If the timing falters, water supplies would shrink. Forests and other wildlife habitat would weaken. Wildfires would grow. Hydroelectric power production would suffer.

"Changes in runoff are only one step away from the warmth in global warming," said Brad Udall, an environmental engineer and director of the Western Water Assessment in Boulder, Colo. "Right after temperature increase, what should pop into people's mind is the question of water."

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