Shrinking snowpacks to affect Northwest

The U.N. global-warming report detailed Friday cites the Columbia River Basin as an example of the water-management challenges in a warming North America.

Though the findings of the report were released, the full chapters aren't yet publicly available. But they include a section that examines the effects of shrinking snowpacks on the Columbia River system, which is crucial to farming, fish and power generation, according to researchers who helped write the report.

The more the snowpack shrinks, the harder it will be for the basin to meet water needs.

"Particularly for the irrigators, you're looking at a worse summertime situation," said Michael Scott, an economist who works for the Richland-based Pacific Northwest National Laboratory.

Scott was one of eight researchers — four each from the United States and Canada — who wrote the North American chapter that distills the results of major climate research across the continent.

The researchers highlight the Columbia River Basin in the North American chapter. Through the end of the century, forecasts assume that overall precipitation in the region will remain the same, but more will fall as rain, and the snowpack will melt earlier.

Under that scenario, Columbia River Basin flows would be higher in the winter and spring but markedly lower in the summer, when water is needed most for salmon, farmers and hydropower sales to California.

To aid salmon, for example, water-flow targets are set for the McNary Dam. By the 2090s, the current targets would be met only about 75 percent of the time, according to the report.

The effects of climate change have yet to be woven into the multitude of recovery plans for salmon and other wildlife throughout the region, Scott said.

Bonneville Power Administration (BPA), which markets the basin's hydropower, is starting to assess effects of global warming.

Snowpack is an important part of the water-storage system, but as it shrinks, there should be ways to catch more of the winter runoff and hang on to it for the summer, said Scott Simms, a BPA spokesman.

"We're still studying this," Simms said.

Increased water conservation by farmers and other major users also could lessen effects forecast in the report, Scott said.

The North American chapter also highlights the impact of global warming on wildfires. The earlier snowmelt and higher summer temperatures could dry out the landscape and create intense fires.

The report notes that this effect already may be under way. It cites a nearly sevenfold increase in total area burned in the West in the 16 years that ended in 2003, compared with the 16-year period that ended in 1986.

"We've had some very good, solid evidence on this," said Steve Running, a University of Montana terrestrial ecologist who helped prepare the fire section of the North American chapter.

The Northwest also will be affected by rising sea levels. The report warns of increased beach erosion, coastal flooding and other damage during high tides and storm surges, said Chris Field, director of the department of Global Ecology at Carnegie Institution and a co-author of the report.

"It means when there is a high-water event, that event is more serious," Field said.

Hal Bernton: 206-464-2581

or hbernton@seattletimes.com