California snowpack melt stirs water worries

By Leonard Anderson

SAN FRANCISCO (Reuters) - Water content in the Sierra Nevada snowpack in California continues to drop toward its lowest level since 1990, raising concerns about the availability of water for generating hydroelectricity and irrigating the state's vast farmlands.

Longer term, scientists have projected that 25 percent of the California snowpack could disappear by 2050 due to global warming and climate change.

State water officials say reservoir storage levels are at or above normal after a very wet 2006 -- the fifth wettest on record in the northern half of the state -- but warn that two consecutive dry years could trigger water shortages.

California's last major statewide drought was 1987-1992.

A survey showed the snowpack in California was only 46 percent of normal in March, down from 64 percent in February, and the water content fell further to 39 percent on Thursday, according to the state's Department of Water Resources.

A big reduction of the snowpack and earlier snowmelt would require more reservoirs to prevent flooding and ensure reliable water supplies, while higher water temperatures would affect the Delta ecosystem in California's farming heartland, reducing water quality and threatening wildlife, according to DWR.

"A warming climate means more water will fall in the form of rain rather than snow, challenging the capacities of existing water reservoirs in parts of the world reliant on snowmelt," a study of climate change effects by the San Francisco-based Global Business Network consulting company said.

"The Western United States and Central Asia are especially vulnerable to this effect," it said.