Dry winter brings more water issues

A possible third dry winter in a row would strain the ecosystems of Southern California, and there’s little water saved in the bank, according to experts speaking during a winter outlook workshop held in San Diego by the state’s Department of Water Resources, it was reported today.

Water managers are closely watching the approaching winter, because California has had two consecutive exceptionally-dry years. The state’s reservoirs are at less than half capacity on average, and court-ordered pumping restrictions to protect endangered fish have caused cutbacks in water deliveries to Southern California, the San Diego Union-Tribune reported.

Many people in the San Diego County backcountry rely on groundwater supplies, which in many places have been diminished by nine dry years out of the past 10.

“We need a better-than-average water year to build the bank account back up,” Jeanine Jones, interstate resources manager for the state’s Department of Water Resources, told the Union-Tribune. On average, half of the annual statewide precipitation falls in December, January and February.

The long-range forecasters said that there was a great deal of uncertainty in their winter predictions.

“There’s some room for a year that at least edges us toward normal precipitation in (Southern California). It’s even possible that we’ll be above normal. But right now, it doesn’t look like a heavy winter in Southern California,” Dan Cayan, a researcher at Scripps Institution of Oceanography in La Jolla and the U.S. Geological Survey, told the Union-Tribune.

On the plus side, the Sierra Nevada and the Colorado River basin, the areas that supply most of the water used by Southern Californians, should get at least normal precipitation.

Jerry Zimmerman, executive director of the Colorado River Board of California, said the past 10 years combined have been the driest on record in the basin, but the last year saw a very-wet Rocky Mountain winter and above-normal runoff into Lake Powell, one of the two major reservoirs in the basin. Not cutbacks in water deliveries from the Colorado River to California are expected in 2009.

Mike Dettinger, a colleague of Cayan’s at Scripps and the USGS, said patterns this year seem to favor a few “atmospheric rivers” of moisture during the winter. These rivers, more than a thousand miles long, could bring intense, multiday storms that would supply much of the year’s precipitation.

“There’s modest hope for a break,” Dettinger told the Union-Tribune.

“Don’t bet the farm on it, but don’t jump out of a window, either.”