Global warming to hit rivers hard, analysis finds

Susan Gordon; The News Tribune

11/21/02

A new analysis of the effects of global warming on major Western rivers concludes temperature increases over the next 50 years will increase friction over the use of limited water supplies.

The predicted changes include reduced snowpack throughout the Pacific Northwest and earlier spring thaws. That means trade-offs in the Columbia River, where summer flows are likely to dwindle, researchers said.

"You can have hydropower or you can have salmon, but you probably can't have both," said Tim Barnett, a marine physicist at the Scripps Institute of Oceanography in California.

Barnett coordinated the Accelerated Climate Prediction Initiative, a 2 1/2-year, $2.5 million project sponsored by the U.S. Department of Energy. Other contributors included experts from the National Center for Atmospheric Research, in Boulder, Colo., the Pacific Northwest National Laboratory in Richland and the University of Washington.

Scientists used sophisticated computers to estimate the effects of climate change on the Columbia, Sacramento and Colorado rivers. Based on their predictions, the Colorado and Sacramento rivers won't be able to deliver the consistent supply of water that users demand for drinking, agriculture and hydropower.

The latest analysis does not anticipate a shortage of Columbia Basin irrigation water but predicts persistent problems in the Yakima River valley, where irrigation supplies already are stretched.

Researchers based their predictions on a conservative climate model that plays down the likelihood of temperature increases.

"This really is giving you a best-case scenario, which is scary," Barnett said.

The new projection for the Pacific Northwest is less dramatic than one completed in 1999 by UW researchers, who performed a similar, but less detailed regional analysis using different computer models.

The new Pacific Northwest forecast predicts a 2- or 3-degree increase in average annual temperatures within the next 50 years. The previous prediction suggested temperatures twice as high.

Even so, Phil Mote, the UW atmospheric scientist who authored the 1999 report, said the new analysis vividly underscores the "grave concern" associated with climate change.

Both studies forecast warmer, wetter winters, with less snow and more rain in the mountains.

The new analysis predicts a 50 percent reduction of the snowpack in the Cascades and 30 percent less in the mountains that feed the Columbia River, said Bill Pennell, one of the research leaders. Pennell, an atmospheric scientist, is director of atmospheric science and global change at the Pacific Northwest National Laboratory.

While some experts dispute the risks of global warming, most scientists agree that excess greenhouse gases, such as carbon dioxide, have altered the earth's atmosphere. Over the past century, average worldwide temperatures have risen about a degree. In the Northwest, the increase has been a little higher.

Most scientists blame industrial pollution and motor vehicle emissions for the increased carbon dioxide and methane, which are likely to remain trapped in the atmosphere for as long as 100 years.

In the short term, nothing can be done to reduce greenhouse gases already there, Pennell said.

"The climate change we're talking about in the next 50 years, we've already bought into. Climate is kind of like a big freight train. It takes a while to get going, and it's going be a long time before it stops," Pennell said.

Consequently, people must adapt. "It's going to force some really tough changes because not all of these conflicts are going to be resolved to everybody's satisfaction," he said.

Some people who worry about how climate change will affect hydropower production and fish already have begun to factor in the likely effects of climate change.

That's true at the Northwest Power Planning Council, which forecasts regional energy demand. System analyst John Fazio has worked closely with the UW researchers who developed the latest predictions for Columbia River flow. The outlook looks grim for salmon, he acknowledged. "We just don't have the storage capacity in our reservoirs to hold that much water to make a difference for fish," he said.

Even so, Kyle Martin, a hydrologist who works for the Columbia River Intertribal Fish Commission, believes climate change could mean a reduced likelihood of spring floods, which could allow the U.S. Army Corps of Engineers to increase the volume of water stored behind dams.

"A lot of water is being flushed out in winter and early spring. That water is literally being thrown away," Martin said. "We're not advocating flooding out lower river communities, but the water would benefit fish and power if it were saved and pushed out later in the year."