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Recent rains haven't done enough,
predicted runoff flows still low |
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June 12, 2015 |
from the Columbia Basin Bulletin
http://www.cbbulletin.com/434232.aspx
Despite recent rains in the Columbia Basin (of
which the Kootenai and Moyie Rivers are
tributaries), it
hasn’t been enough to alter forecasts for low
river flows between now and September.
Taylor Dixon of the National Weather Service’s
River Forecast Center in Portland gave a June 4
teleconference presentation on weather and river
flows, and the storyline of the last few months
persists.
“Temperatures have played the biggest role in
things this year,” he said, adding that there
was more rain than snow compared to 30-year
averages, there was an earlier than normal
snowpack melt followed by an earlier than normal
runoff.
Dixon stressed that the overall precipitation
picture since last October was actually close to
average, and in many drainages throughout the
basin, it was even better than last year’s
overall precipitation.
“Overall runoff is not far from normal but the
timing of it has been abnormal,” Dixon said.
Runoffs were higher than normal in most Columbia
Basin river drainages up until April, but after
that, they dropped precipitously.
At The Dalles Dam on the Columbia River, for
instance, flows from October through June 3 has
been at 102 percent of average, but between
April 1 and June 3, flows have been at 77
percent of average.
That does not reflect dry conditions west of the
Cascades, where record-low volume flows are
forecasted through September: 61 percent of
normal on the Skagit River; 36 percent on the
Dungeness River; 46 percent of on the Cowlitz
River; 44 percent on the Lewis River; 59 percent
on the McKenzie River; 42 percent on the South
Santiam River; 46 percent on the North Santiam
River; 50 percent on the Willamette River; and
49 percent on the Clackamas River.
The outlook is somewhat better east of the
Cascades, largely because river flows are
augmented by higher elevation basins in Canada,
Montana and Idaho, Dixon said.
Flows through September at The Dalles Dam on the
Columbia River are expected to be 72 percent of
average, a forecast that has not changed since
an early May River Forecast Center update.
However, Dixon said that unexpected, increased
diversions from upstream drainages, for
agricultural or other purposes, could lead to
lower flows.
Flow forecasts for other rivers through
September include 91 percent of normal on the
Columbia River at Arrow Lakes; 81 percent on the
Kootenai River in Montana; 68 percent on the
Clark Fork at Cabinet Gorge; 43 percent on the
Spokane River (a record low); 79 percent on the
Columbia River at Grand Coulee Dam; 72 percent
on the Snake River at Shelley; 50 percent on the
Snake River at Brownlee Dam; 56 percent on the
Snake River at Granite Dam; 33 percent on the
Grand Ronde; 38 percent on the John Day River;
and 36 percent on the Yakima River (a record
low).
There is currently a statewide drought
declaration in Washington, and drought has been
declared in 15 Oregon counties and five Idaho
counties.
And the National Weather Service’s three-month
outlook weather outlook does not indicate there
will be a change to the trend. Dixon said there
is an above-normal chance there will be
above-normal temperatures, but he said the
outlook for rain is difficult to pin down,
especially with a three-month forecast.
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