[pf] California water plan: smaller Sierra snowpack

http://www.sfgate.com/cgi-bin/article.cgi?file=/chronicle/archive/2001/06/15
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Global warming to affect water supply 
More rainfall means smaller Sierra snowpack

David Perlman, San Francisco Chronicle Science Editor;  Fri., June 15, 2001 

California water planners face a problem they never thought they'd
encounter: global warming is hitting the High Sierra snowpack. And just how
the planners cope with it could affect every city-dweller, every farmer and
every water-using industry in the state for years to come. 

Scientists are in broad agreement that the world's climate is steadily
warming -- whether due to "greenhouse gas" emissions from industry and
automobiles, or to natural variability. And there is evidence that it is
already altering the annual ebb and flow of the state's water supplies. 

It's a matter of "more rain, less snow," says Dan Cayan, director of the
climate research division at the Scripps Institution of Oceanography in La
Jolla (San Diego County). And that's bad, he says, because California's
water supply largely depends on the winter snowpack in the high mountains
that must feed the state's lowlands the rest of the year. 

A major change is already evident in the decreasing depths of the mountain
snows that pile up each winter, in the unseasonal winter rainfalls that
drench the mountains instead of snow, and in the speed of the snowmelt
during spring. 

Total precipitation over California hasn't changed significantly on average
over the years, but seasonal variations between rain and snow show that a
significant warming trend is under way, according to Cayan. 

Annual surveys of mountain snow depths and water levels of California's
major rivers show that before the 1960s runoff in the late spring and early
summer amounted to a good 40 percent of the total runoff each year, Cayan
said. 

But since the mid-1970s, runoff during the late spring and early summer has
dropped to barely 30 percent of the annual total, he said. 

Peter Glieck, a hydrologist and climate specialist who heads the Oakland-
based Pacific Institute for Studies in Development, Environment and
Security, a nonprofit research organization, has tracked California's
changing climate record for many years. He says his findings add powerful
evidence that the warming trend is real. 

"The problem of managing the state's water resources more rationally in
view of the changing climate is urgent now," Glieck says. "We need detailed
studies to decide what to do. Studies are a lot cheaper than floods." 

Officials of the California Department of Water Resources are starting to
look at the effects of climate change as they develop the 2003 California
Water Plan that state law requires the department to produce every five
years. 

"I can look at the Sierra summit right now, and there's no snowpack at all
up there, while the major reservoirs downstream are full," said Jonas
Minton, deputy director of the California Department of Water Resources,
speaking from his office in a Sacramento office tower. "The warming problem
is just beginning, but it's certainly focusing our attention." 

As Minton sees it, the warming trend poses at least three increasing dangers: 

-- Severe lowland flooding as rains in the winter replace mountain snowfalls; 

-- Rising sea levels that reach into the Sacramento-San Joaquin River Delta
and threaten century-old levees that must protect the rich croplands; 

-- The intrusion of salt into Delta waterways that disturbs both fisheries
and the natural delta ecology on which farmlands depend. 

How the Department of Water Resources hedges against these changes are what
Minton and the department's experts must contend with over the next two
years as they develop the state water plan. 

The last such document in 1998 included forecasts for the state's water
supply and demand over the coming 20 years, and provided recommendations
for dam building, flood control, water management and conservation
measures. Now, the department is gearing up to draft the plan for 2003. 

On Wednesday in Los Angeles, Cayan, Glieck and other experts will offer the
department's 60-member advisory committee the latest evidence that the
warming problem could grow steadily worse. 

The Water Department has a 60-member advisory committee made up of
"stakeholders" -- the people most affected by water policies like
agricultural water districts, urban water departments, food processing
industries and public utilities. All provide input for the state's water
planners. The committee meets every two months or so for the next two years
until the final plan is released. 

E-mail David Perlman at: dperlman@sfchronicle.com .
 

©2001 San Francisco Chronicle   Page A - 3 
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sent-on by David.
(David MacClement) davd@ihug.co.nz 
http://www.geocities.com/davd.geo/index.html#top
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