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Global warming to hit California water supply - study

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USA: June 6, 2002

 

 

SAN FRANCISCO - Global warming will bring hotter temperatures and depleted

snowpacks to California over the next several decades, boosting demands on the

state's already strained water supplies, according to a new study.

 

 

" With less precipitation falling as snow and more as rain, plus higher

temperatures creating increased demand for water, the impacts on our water

storage system will be enormous, " said Lisa Sloan, an associate professor of

Earth sciences at the University of California-Santa Cruz (UCSC) and an author

of the new research.

" When you overlay that with our projected population increase, you are looking

at a very serious situation, " Sloan said Tuesday.

 

The UCSC study, to be published this week by the journal Geophysical Research

Letters, examined a computer model of the regional climate system to plot the

effect of rising concentrations of carbon dioxide, the heat-trapping " greenhouse

gas " released by the burning of fossil fuels.

 

Specifically, the study examined the atmospheric effects of carbon dioxide

levels, predicted to rise to as much as twice the levels seen before industrial

development by as early as 2050.

 

The results confirmed what many environmental scientists have suggested will be

the likely impact of global warming on California, already the nation's most

populous state and expected to be one of its major engines of future growth.

 

Fueled by both domestic and overseas immigration, California's population has

been forecast to grow to as many as 54 million people by 2025 - adding some 20

million people to a state already thirsty for water.

 

The UCSC model showed that thirst growing worse, with global warming leading to

higher average temperatures every month of the year in every part of the state.

 

The greatest warming - as much as 11 degrees Fahrenheit (6.6 degrees Celsius) -

was predicted to hit high elevations of the Sierra Nevada and Cascade mountains,

where the seasonal snowpack has long been an important " water bank " to carry dry

California through the hotter summer months.

 

82 PERCENT LESS WATER

 

While rainfall was predicted to rise in the northern part of the state and

remain relatively stable in southern California, snow levels were likely to drop

off sharply due to the rising temperatures, the study said.

 

The study suggested that in March, for example, the Sierra snowpack would be

roughly 13 feet (3.9 metres) lower than it is now. By the end of April, the

snowpack would be almost completely gone.

 

" In water terms, by the end of February there will be 82 percent less water than

there is now, " Sloan said. " We are talking about a real shift in amount of water

coming to the state, and the timing of it. "

 

That could mean big trouble for California, where roughly two-thirds of the

state's residents depend on water from the Sierra stored and transferred through

a large network of dams and irrigation canals.

 

The UCSC research was aimed at deriving results for an " average " year based on

15 years worth of data generated by the model for each carbon dioxide

concentration.

 

The researchers said their model, by focusing on California data, revealed a

much more detailed picture than was previously available of the likely impact of

global warming in regions ranging from the Coast Ranges and the Central Valley

to the Mojave Desert and the Sierra Nevada.

 

While the results were statistically significant, Sloan said, they were not

" predictions " and could change if the rate of carbon dioxide concentration

changes or other unexpected environmental factors came into play.

 

But she added that even major declines in greenhouse gas production, such as a

wholesale adoption of nuclear power in the developed world, would still not

prevent some of the climate changes already underway.

 

" Even if you assume some pretty drastic changes the greenhouse gases will still

probably increase for a couple of centuries, so our scenarios may still fit a

range of actual conditions, " Sloan said.

 

" You might even come to the conclusion we are looking at a low end of the

climate change. "

 

 

 

 

Story by Andrew Quinn

 

 

REUTERS NEWS SERVICE