Climate change upon Y-S?

SACRAMENTO - Global climate change could be felt in Northern California with bigger floods, more intense rainstorms and less spring runoff to feed thirsty cities, the Department of Water Resources chief hydrologist said Friday.

Maurice Roos spoke about climate change and water in California to the state Reclamation Board in Sacramento. He explained data on runoff and precipitation projects, and outlined some of the possible long-term effects on California climate.

If precipitation is about the same, warmer temperatures would mean more winter runoff followed by smaller volumes of spring and early summer snowmelt.

One key change for Yuba, Sutter and Colusa counties - where four rivers run through - is a possible shift to higher snow levels during winter storms. Each one-degree Celsius rise in temperature would raise the snow level 500 feet.

Higher snow levels would mean less of the precipitation would be locked up high in snow. The result would be more winter runoff and floods.

“If you turn the whole Sierra into a rain zone, you’re going to have floods more often,” said Roos, in an interview after his talk.

Higher elevation snow can be a problem because snow stays up on the mountain while rain flows downhill. The Yuba-Sutter area is protected against all but extreme storms by Oroville Dam.

But the system was tested in 1997 when a warm “Pineapple Express” storm, coupled with low-elevation snow, threatened to send a large amount of water over the dam’s emergency spillway, prompting Yuba-Sutter to evacuate.

While climate change is a long-term problem, temperatures seem to be getting warmer now. The Western Region Climate Center shows temperatures that have gone up a degree or so, said Roos. That is contested by some who believe bigger cities are contributing to higher temperatures.

“There does seem to be some changes,” Roos said.

The Intergovernmental Panel on Climate Change, comprised of a global team of scientists, projects that extreme events like floods will be more likely by the year 2100, said Roos.

Climate change could make it tougher to fill Lake Oroville, which is already quite difficult to fill now. The standard practice is to keep enough reservoir space in winter to catch big storms, then top off the reservoir with spring runoff after flood season.

But with global warming, there would be less spring runoff to catch.

Cold-water fish like trout and salmon could also be hurt by warmer water temperatures.

And farmers’ fields would experience more evaporation, meaning that more water may be needed.

Though long-term prospects for more floods could be worrisome, Roos noted there are plenty of more immediate problems, such as levee improvements.

The good news, according to John T. Andrew, chief of special projects for the department, is that climate change is going to unfold incrementally and over water systems that have some flexibility. Andrew also spoke at Friday’s Reclamation Board meeting.

Gov. Arnold Schwarzenegger passed an executive order in June 2005 that recognizes global climate change and establishes greenhouse gas emission targets.