Glen Martin / SF Chronicle 15dec00
A new report on global warming admonishes California to change the way it manages its reservoirs or face severe water shortages and catastrophic flooding.
And even if water policies change, warns the report being issued today, climatic warming from increased atmospheric greenhouse gases probably will intensify the state's already severe energy woes.
The two-year study sponsored by the U.S. Geological Survey and the Pacific Institute, an Oakland think tank specializing in environmental issues, notes that under a scenario of more greenhouse gas emissions, precipitation may actually increase in the state.
But the report warns that Californians will not be able to make much use of the water unless reservoir policies are changed radically.
Prognostications for other states in the West are even grimmer. The region is expected to be significantly hotter and drier by the middle of the 21st century, resulting in reduced water resources.
The study predicts the Colorado River system could be particularly hard-hit,
resulting in curtailed water deliveries to Arizona and Mexico.
Because it has senior water rights, California is expected to monopolize much of the Colorado's reduced yield.
The report also warns of widespread environmental havoc throughout the West as higher temperatures and disrupted precipitation patterns alter long- established ecosystems. Cold-water fish such as salmon and steelhead are apt to suffer especially steep declines.
Peter Gleick, the director of the Pacific Institute and the lead author of the report, said water analyses were conducted on two established global warming models -- the Hadley Model, which was developed in the United Kingdom, and the Canadian Model.
"Both predicted significantly more precipitation for California by 2030," Gleick said. "The Hadley Model predicts about 8 percent more, and the Canadian Model predicts up to 16 percent. By the end of the century, temperatures are expected to rise by six to nine degrees."
Though the increased precipitation may seem like good news, it presents serious problems to water managers, Gleick said.
"Basically, more of it will fall as rain and less as snow than is now the case," Gleick said. "That will make the runoff more difficult to manage."
Currently, water managers draw reservoirs down by late summer to ensure adequate flood control capacity for the following winter. Reservoirs often aren't allowed to begin filling in earnest until the spring runoff resulting from snowmelt.
But if California is to meet its mushrooming demand for water and hydropower, Gleick said, it must change the way it stores water.
"If we don't want unpleasant surprises, flood control space may have to be filled faster," he said."
That means that reservoirs will probably have to be filled during big storms, since snowmelt will be relatively scant.
"We can say with a high degree of confidence that there will be far less snowpack," said Gleick. "The Sierra will certainly lose all its remaining glaciers, and that will be repeated across the West. Glacier National Park (in Montana) is expected to be glacierless by the end of the century."
But such a strategy will require precise timing, said Gleick. If managers aren't aggressive enough in filling reservoirs during rain storms, they may end up with insufficient supplies to satisfy state water needs.
But if conditions aren't monitored closely enough during wet weather, reservoirs could brim too quickly, resulting in severe downstream flooding.
Still, said Gleick, there probably will be no reasonable alternative to doing things differently in a warmer world.
"A study was conducted on Folsom Dam on the American River near Sacramento, " said Gleick. "Under one scenario, there could be up to $4 billion in flood damage in Sacramento (from the American River flooding) if current reservoir rules are followed. But if the dam was operated under revised rules, damage could be reduced to $220 million."
Folsom is one of more than 20 California dams managed by the U.S. Bureau of Reclamation, according to agency spokeswoman Lynnette Wirth.
"We have read the literature (on global warming), but we haven't really participated in the discussion," said Wirth. "Given the current information, we are not now considering changes in (operating) policy."
Wirth said the agency is acutely aware of California's limited supply of water "and we're doing what we can to stretch it."
If reservoirs are closely monitored, said Gleick, dams should supply as much hydropower as they do now. But global warming probably will still exacerbate the state's energy crisis, he said.
"Temperatures are almost certain to be higher in coming years, and higher temperatures hurt us from an energy point of view," said Gleick. "In California, the peak demand for energy comes during the air conditioning season, when temperatures are highest."
If proper planning is conducted, Californians can adjust to some of the impacts of global warming, Gleick observed -- but that won't be necessarily true for the state's fish and wildlife.
"In a general sense, you could expect (wildlife) species to shift northward, " Gleick said. "But the question is whether they can do that or not, inhibited as they are by such things as development.
E-mail Glen Martin at gmartin@sfchronicle.com
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