Local rivers rise with spring snowmelt
The Methow Valley is expected to experience moderate drought this summer, based on the latest water supply and climate projections.
Across the state, precipitation in April was much below normal and temperatures were slightly above normal, and mountain snowpack is disappearing rapidly, said Scott Pattee, water supply specialist with the Natural Resources Conservation Service (NRCS).
While areas just east of the Methow Valley are projected to have an extreme drought this summer, the Methow Valley’s outlook is somewhat better, largely due to a good snowpack that accumulated last winter at high elevations in mountains above the valley, Pattee said.
At Hart’s Pass, which has the highest snowpack measurement site in the state, the snowpack on Tuesday (May 12) was 91 percent of normal for that date, and Rainy Pass snowpack measured 95 percent of normal, Pattee said.
Snowpack measurements indicate the amount of water held within the snow, which serves as a reservoir that feeds rivers and streams as it melts in the spring. Farmers, fish and wildlife, and recreationists depend on the supply of water from the mountains during the hot, dry months of summer and fall.
“The snowpack up high was really good. That’s what’s supporting the outlook [for the Methow Valley] right now,” Pattee said. However, the snowpack was melting fast since the beginning of May.
“Harts Pass over the last 12 days has lost 11.6 inches of snow water content,” Pattee said on Tuesday. Water content was 43.3 inches on May 1 at Hart’s Pass, so more than one-fourth of the snowpack had disappeared in less than two weeks.
High elevation snowpack accumulation was greater this past winter than the previous winter, Pattee said. At Harts Pass, snowpack was 102 percent of normal on May 1 this year, compared to 83 percent of normal on May 1, 2109. However, the rate of spring melting was very different.
“We had two totally opposite springs. Last year stayed really cool, so snow came off really slowly. This year it’s coming off at a normal rate or ahead of normal,” Pattee said. A quickly disappearing snowpack can lead to water shortages for irrigators and other users later in the year.
The melting mountain snowpack was increasing flow in local rivers in recent weeks. The Methow River was running at about 144 percent of normal on May 12 at the streamflow gauge in Winthrop, and 156 percent of normal at the gauge at Pateros, Pattee said.
The Methow River is projected to run at about 88 percent of normal during May through September, according to NRCS forecasts.
This past winter was marked by a lack of snow at lower elevations in mountains throughout Washington, contributing to expectations for drought for much of the state, Pattee said. The forecast for May predicts above normal temperatures and equal chances for precipitation. The National Weather Service three-month forecast for May-July indicates above-normal temperatures and below-normal precipitation.
Precipitation in April in the Upper Columbia Basin, which includes the Methow Valley, was only 52 percent of normal for the month, according to NRCS. The Upper Columbia has received 81 percent of normal precipitation for the water year, which is measured from October through September.
The National Inter-Agency Fire Center released its latest wildfire outlook for July and August, which indicates an above-normal chance of wildfire for most of eastern Washington, and normal conditions on the west side of the Cascade Mountains (see related story, page B1).