Where there's snow, there's water

High moisture content means good news for irrigators

Cookson Beecher
Capital Press

February 08, 2008

While current snowpack levels are good news for irrigators in the Pacific Northwest and California , even better news is the moisture content of those snowpacks.

"When the snow melts, it's good for irrigators, so moisture content is a more meaningful quantity," said David Garen, Natural Resources Conservation Service hydrologist in Portland , Ore.

The snow-water equivalent represents the depth of water in the snowpack, expressed in inches, if the snowpack were melted.

Jon Lea, NRCS snow survey supervisor for Oregon , said moisture content generally started out low, with the Owyhee Basin 's moisture content at only about 42 percent of average in mid-December.

But as of Feb. 5, there was marked improvement. By then, the snowpack moisture content was 110 percent of average.

Above-average moisture content can be seen in the state's other basins as well.

"It's unusual to have averages that are above average across the state," Lea said. "All of this is very good news."

Good snowpack and moisture content are especially important this year, he said, because many irrigation reservoirs were drained last near.

"We need more moisture to get the reservoirs back up," he said. "It looks like we're getting it."

In Washington state, the picture also looks good. Scott Pattee, NRCS water supply specialist for Washington state, said there are no problem basins.

The lowest readings in early February were in the northeast corner of the state, where moisture content was slightly below normal.

"Everything is looking pretty good, as long as our current jet stream flow coming from Alaska continues, with wave after wave of normal precipitation," Pattee said.

In Idaho , snowpack moisture content as of Feb. 5 also held good news for irrigators. The basins south of the Snake River are near average. The Owyhee Basin was at 110 percent of average, and the Salmon Falls Basin was at 106 percent of average.

In the Bear River Basin , moisture content was 97 percent of average, while in the Snake River Basin above the Palisades , it was 95 percent of average.

"Right now snowpack is much better than last year," said Ron Abramovich, NRCS water supply specialist for Idaho . "We'll need near-normal snowpack or better on April 1 for irrigation this year."

A troubling situation for irrigators is that the Palisades Reservoir and Jackson Lake are at only 37 percent of capacity, compared with last year when they were at 72 percent of capacity.

The Magic Valley Reservoir, which was at 60 percent last year is at only 11 percent capacity this year.

"We used almost all of the water in the reservoirs in Southern Idaho last year," Abramovich said.

According to "early-bird" stream-flow forecasts in Washington , Oregon , Idaho and California , all but a few monitoring sites are showing normal conditions.

The majority of the spring and summer runoff in Central and Southern Idaho is from snow runoff coming from 6,000-foot elevations or higher. Abramovich said Mother Nature typically sees to it that snow at those high elevations gradually melts at a rate of about 1 to 2 inches a day when the weather starts getting warmer.

In California , snowpack moisture content is also looking good.

In the north section of the state - Trinity through Feather and Truckee - the average was 129 percent of normal as of Feb. 5.

In the central section of the state - Yuba and Tahoe through Merced and Walker - it was 115 percent of normal.

And in the south section of the state - San Joaquin and Mono through Kern - it was 131 percent of normal.

"It's all above normal," said Marianne Hallet, NRCS water supply specialist for California . "We like that."

Another plus is there's still quite a lot of winter left. "We'd like to see this weather continue," she said. "We're getting above-average rain and snow. I'm cautiously optimistic. It all depends on the weather that follows."

According to "early-bird" stream-flow forecasts in Washington , Oregon , Idaho and California , all but a few monitoring sites are showing normal conditions.

Stream-flow forecasts for Washington , Oregon and Idaho are at www.nwrfc.noaa.gov/espws/espws/cgi.

The same information in California is at www.cnrfc.noaa.gov.

Staff writer Cookson Beecher is based in Sedro-Woolley , Wash. E-mail: cbeecher@capitalpress.com. 

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