Despite Lots of Rain, Summer may be Dryby Stuart Tomlinson
The Oregonian, January 31, 2003
There has been plenty of rain -- including record amounts in some areas, and flood warnings on many rivers Thursday -- but not enough cold weather to make it stick in the mountains.
Winter snowpacks are important because they are like water in the bank. After accumulating snow all winter, mountains release their stored water during the region's dry period, typically June through September.
"It's the classic irony of water supply in the West," Oregon state climatologist George Taylor said. "Most of the precipitation falls at high elevations, and most of the demand is at low elevations. Most of the precipitation falls in winter, and most of the demand is in summer.
"And there are two ways that that water becomes available at low elevations in the summer: No. 1 is snow, and No. 2 is reservoirs," Taylor said.
Oregon's snowpack is thin. In one month, the snow at a Mount Hood measuring site at 5,400 feet has dropped from about 55 inches to 36 inches deep, or 34 percent of average. A typical snowpack this time of year at the measuring site is usually more than 100 inches.
Snowpacks in parts of Eastern Oregon are better, but not by much, with most running 60 percent to 70 percent of average. In general, the farther north you are in Oregon, the drier it gets.
Snow levels are expected to fall as low as 2,500 feet by Saturday, but some forecasters said most of the moisture will be wrung out of the clouds after two days of heavy rain.
"It doesn't bode well for future snowpacks," said hydrologist Jon Lea of the Natural Resources Conservation Service. "About 70 percent of our snowpack is usually on the ground by Feb. 1."
Oregon's snowpack is the second worst in the West at 49 percent of average. Only Arizona is worse at 39 percent. Washington's combined snowpack, at 61 percent of average, is fourth worst in the West, just behind Montana at 69 percent of average.
But not so fast, said Taylor, who is predicting a wet and cold February and March.
"Those two months often bring the most snow to the higher elevations of Oregon," Taylor said. "We could get a couple of feet of snow this weekend . . . winter's not over yet."
Taylor said it's not that unusual to be talking about drought on the same day the National Weather Service issued flood watches for seven rivers on the Oregon coast and about a dozen rivers in Southwest Washington.
Those warnings came the day after Portland, Astoria and Corvallis had record rainfall amounts. Another 2 to 4 inches of rain was expected to fall through Sunday, adding to more than 3 inches that has already come down this week.
Oregon rivers with the potential to flood include the Wilson, Alsea, Siletz, Clackamas, Luckiamute, Marys and Siuslaw. Most rivers are expected to crest late tonight or early Saturday.
Although Portland is about 3.5 inches below normal for the water year (measured from Oct. 1 through Sept. 30), Corvallis, Medford, Pendleton and Burns have had near or above normal rainfall.
Several years ago, Taylor said, Umatilla County was in the midst of a long-term drought when it had flooding.
"Drought is long term, and flooding is short term," Taylor said. "Climate is what happens over the long term, and weather is what happens today."
It's the long term that concerns Kyle Martin, a senior hydrologist for the Columbia River Inter-Tribal Fish Commission. Martin looks at long-term weather patterns and how they affect salmon in the Columbia River. And what's good for fish is good for generating electricity.
Martin said all of the basins that feed the Columbia River are either abnormally dry, or in moderate to severe, or even exceptional drought. If his forecast is true, the amount of runoff available for fish and hydroelectric power for the Columbia River at The Dalles Dam would be 60 percent of normal, the fifth-lowest on record.
Most reservoir operators are required by law to allow room for springtime floods, so much of the rain that is falling is just running downstream, leaving less water for hydroelectric power, recreation and salmon this summer.
The culprit for all of this has been a moderate El Nino, a warmer than normal sea-surface temperature pattern in the eastern Pacific Ocean that brings colder than normal weather to the East Coast and dry conditions to the West.
"You might not believe it by looking out the window, but not much of this rain is going into the snowpack," Martin said. "We're looking at a really dry period in February, March and April, starting next week.
"We could be facing a really dry summer."
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