Record-breaking dry spell bodes ill

Science: Regional water supplies not yet hit by lack of rain

JOHN DODGE; The Olympian | • Published July 10, 2009

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South Sound is on pace for a record-setting dry summer, according to the National Weather Service.

The last time any significant rain fell in most of Western Washington was May 19, including 0.40 inches in Olympia.

From May 20 to July 4, precipitation in Olympia was 0.23 inches, which shattered the previous dry mark for the same, 46-day period of 0.40 inches set in 1965.

“Essentially summer started abruptly in Western Washington on May 20,” said Phil Mote, research scientist with the University of Washington’s Climate Impacts Group.

Olympia is not the only community in the record books for a dry late spring and early summer. Sea-Tac International Airport registered 0.18 inches, compared with 0.64 inches in 1965. Hoquiam measured 0.40 inches, compared with the previous record of 0.78 in 1965.

Meanwhile, the 90-day weather outlook by the National Weather Service’s Climate Prediction Center is for less-than-normal rainfall.

The abnormally dry weather has yet to effect South Sound water supplies, which rely almost exclusively on groundwater, water resource managers reported last week. Typically, there is a several month lag between dry weather and changes in groundwater levels.

However, recent research by the UW-CIG shows that the amount of rainfall — not just snowpack — largely determines river flows in Western Washington in late summer.

For example, during the summer drought of 2003, when 0.41 inches of rain fell in Olympia from May 20 to July 4, most rivers in Western Washington had record-low flows in August and September.

“We’re particularly concerned about the northern Cascades and Olympic mountains because those areas were already dealing with lower than normal snowpack before this dry spell,” Mote said. As of April 1, snowpacks in those two regions were 67 percent to 77 percent of normal.

Private and public forestland owners alike are keeping a close eye on the weather and the growing threat of forest fires. Last week, a suspected arson in the Capitol State Forest scorched 17 acres.

Statewide, fire danger is ranked “high” in 14 counties, including much of Eastern Washington, and “moderate” in most Western Washington counties, including Thurston and Mason counties, according to the state Department of Natural Resources.

“It is shaping up to be a season of concern,” noted Patti Case, a spokeswoman for Shelton-based Green Diamond Resource Co. “Some people may think the little bit of rain we’ve had this week will let us off the hook, but that’s not the case.”

An outdoor burn ban is in effect in Mason and Pierce counties and goes into effect in Thurston County at 12:01 a.m., Wednesday.

John Dodge: 360-754-5444

jdodge@theolympian.com