pieces are in place for a robust water year in the Columbia Basin states, with
above-to-well above average snowpacks that are beginning to ripen for runoff in
the coming months.
notable have been snow accumulations in the central Idaho mountains that feed
the Salmon and Upper Snake River basins.
year’s mountain snowpack just keeps getting better,” the Natural Resources
Conservation Service states in an early March report for Idaho. February storms
brought abundant precipitation in the state resulting in record or near-record
snow water contents in central Idaho, and significantly, much of the most
recent snow has accumulated at mid and high-revelation automated snow measuring
of the beginning of March, 24 SNOTEL sites in Idaho and western Wyoming have
snow depths over 100 inches,” the NRCS reports. “Deadwood Summit, elevation
6,890 feet in central Idaho is the highest with 147 inches of snow depth.”
several sites, including Deadwood Summit, precipitation was nearly five times
normal February amounts, the NRCS reported, adding that many low-elevation
sites have lost their snowpack already, causing flooding problems. But the bulk
of the snowpack remains.
a result, gates are open on many reservoirs to make room for when the mid-and
high-elevation snow melts,” the NRCS report states.
current water supply conditions have been taking shape for months. “Abundant
October precipitation likely saturated soils across most of the state,” the
Idaho NRCS stated. “Some soils are still frozen due to colder-than-normal
temperatures, which may reduce soil moisture infiltration rates.
is interesting to note that after last month’s melt of valley snow, a fast
response in streams followed a rain event,” the report continues. “This likely
means soils are still saturated or frozen.”
this may translate to an increased, prolonged runoff. Idaho’s water supply
conditions at several mid-to high elevations appear to be as high or higher
than they have been for early March in 2011, 1998, 1997, 1984 and 1983.
Northwest River Forecast Center held its monthly briefing on Thursday, April 6,
again highlighting the heavy snow conditions in Idaho and pointing out that the
water supply forecast for all other parts of the Columbia Basin appears to be
above normal, with similar cold and wet weather being the norm in recent
Kevin Berghoff noted that the upper elevation snowpack appears to be much
heavier than it was last year. Last year, however, an unseasonably warm April rapidly
diminished what was considered to be a healthy snowpack.
said snow at lower elevations has been melting across the basin, and it has
caused a “substantial flooding issue through much of Idaho.”
Idaho Statesman has been reporting on flooding at locations along the Boise
River, mostly "parks, fields, roads and other riverside open areas.” Emergency
response personnel have been taking actions to counter current high water and
they are preparing for worse flooding later this spring when Idaho’s mountain
snowpack melts out.
Statesman reports that managers don’t believe there is enough space in
reservoirs upstream from Boise to manage the runoff; the river’s reservoir
system was already 67 percent full this week.
supply conditions are looking good, despite the first snow melting at lower
elevations at sites on the Cascade Mountains, and at lower elevation sites in
northern Washington, Idaho and Montana.
of these snowpacks are getting increasingly ripe,” Berghoff said, signaling the
annual runoff is getting underway.
outlook is for a robust streamflow from April through September, mainly due to
cold and wet weather that has persisted throughout March.
that five-month period, the water supply forecast is 107 percent of average at
Mica Dam on the Columbia River in British Columbia; 117 percent at Libby Dam on
the Kootenai River; 117 percent on the South Fork Flathead River, Hungry Horse
Dam; 114 percent on the Spokane River; 114 percent on the Columbia River, Grand
Coulee Dam; 141 percent on the Snake River at Jackson Lake; 168 percent on the
Snake River, Palisades Dam; 202 percent on the Snake River, American Falls Dam;
140 percent on the Snake River, Lower Granite Dam.
April through September water supply at seven Washington sites on the Cascades
are at 102 percent to 116 percent of average; and at 12 Oregon sites on the
Cascades, the five-month streamflow forecast ranges from 94 to 134 percent of