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Columbia Basin Starts Year with Low Snowpack

by Barry Espenson
Columbia Basin Bulletin - January 5, 2001

An atypically dry start to the winter season means that without a big mid-winter outpouring Columbia-Snake river fish managers and hydro operators could next spring and summer face serious dilemmas about how to mete out a limited water supply.

At the start of the New Year, the snowpack that feeds the basin's rivers and streams was anything but bountiful. The basin above Washington's Grand Coulee Dam set a new low with 55 percent of its normal snowpack for Jan. 1, according to USDA's National Resources Conservation Service National Water and Climate Center. The previous record was set in 1961.

According to Corps of Engineers officials, that snowpack above Grand Coulee can provide as much as half of the Columbia's flow as measured at The Dalles Dam.

The 2001 Columbia Basin snowpack starts out very low, with many subbasins in the 50-60 percent of average range, according to the NRCS.

The snowpack for the Columbia in Canada above Arrow Lakes is the lowest in the basin at 52 percent, and all subbasins from Spokane north are in the 50's.

The Snake River headwaters hold the best snowpack at 79 percent of average for Jan. 1, followed by the Deschutes in Oregon at 75 percent. Washington's subbasins generally had Jan. 1 snowpacks less than 65 percent of average, with the Yakima River at 64 percent. Central Idaho is in the low 70s overall, but the Salmon River snowpack starts the year at 63 percent and the Clearwater was at 61 percent.

The National Weather Service preliminary water supply forecast compiled at the end of December shows the third-lowest projection on record for flows at the Columbia's The Dalles Dam for the January-July period -- 75 percent of the historic annual average flows recorded since 1970. The NWS's Northwest River Forecast Center in Portland produces its water supply forecasts by gauging to-date precipitation and snow accumulations and forecasts of precipitation and temperature regimes.

The preliminary 2001 forecast is for 79.5 million acre feet of water to pass The Dalles during that period. The record low forecast was in 1977 -- 75.7 maf, according to the forecast center's hydrologist in charge, Harold Opitz. Forecast precipitation did not materialize that year so the actual observed volume past The Dalles was only 53.8 maf.

The record high (since 1970) was in 1997, when 138 maf was forecast and 159 maf actually flowed past The Dalles.

Optiz said the NWS was forecasting near average precipitation for the remainder of this winter. If that happens, snowpacks would build but would not reach average conditions.

A pre-Christmas burst of wet weather helped somewhat to pad Oregon Cascade snowpack totals but had little impact elsewhere in the Basin, Opitz said. Most of the basin's subbasins have recorded below average precipitation since September, he said.

"I remain optimistic," said Paul Wagner of the National Marine Fisheries Service. "It's surprising the degree of variability within a year." Historically, some water years start slow and finish with rapid snow accumulations, and vice versa.

Many of the measures outlined in NMFS' hydrosystem biological opinions to aid fish passage and migration-- such as spill and prescribed flow levels -- are dependent on the water supply.

"If the precipitation doesn't come at some point during the winter it won't be a pleasant spring" and summer, Wagner said. The Technical Management Team has an intensive schedule of meetings during the spring and summer in attempt to make hydrosystem operational adjustments aimed at benefiting migrating, listed fish while minimizing disruptions in power generation, flood control and other system purposes. The TMT is made up of state, federal and tribal fish managers as well as representatives of agencies involved in dam operations and power marketing.

A water shortfall could pose numerous dilemmas. For example, flows would be available for springtime migrants but, in a low water years, TMT may have to decide how much to release and how much to hold behind reservoirs such as at Grand Coulee to meet BiOp June 30 refill targets, Wagner said. That saved water has many uses -- irrigation, recreation and resident fish -- in addition to buoying summer-fall migrants.

The Corps of Engineers has taken notice, releasing water at minimum flows from dams such as Libby in Montana and Dworshak in Idaho with the aim of filling up to required flood control levels.

The "early bird" water supply forecasts are made with much of the winter left but need to be heeded.

"That's the best information we have at this time. You have to put some level of confidence in them," said Cindy Henriksen, head of the Corps' Reservoir Control Center.

The NRCS' Jan. 1 Columbia Basin snowpack totals above The Dalles represent 26 percent of the average "peak" accumulation, which normally occurs around April 1. In an average year, nearly 45 percent of the peak snowpack would have settled on the ground by Jan. 1. Basinwide the snowpack was 59 percent of a normal for Jan. 1. The NRCS noted similar "dry starts" in 1970 and 1988. Only 1977 was drier.

"By mid-January we have a lot of the snowfall and those percentages wouldn't change a lot," said Dan Moore, NRCS Columbia Basin hydrologist. The NRCS, in coordination with the NWS, will update the streamflow forecasts within the coming week, he said.

"If we're lucky and things get started this month I would hope the percentages would go up 10 percent," Moore said. Pushing snowpacks up higher than that would take a considerable onslaught of wet weather at this point in the winter, he said.

Kyle Martin, hydrologist for the Columbia River Inter-Tribal Fish Commission, called the water supply forecast "dismal." Unlike the NWS, he predicts January-March precipitation will be 70-90 percent of normal near Portland, the Columbia Gorge and on tribal lands in Oregon, Washington and Idaho. CRITFC staff provide technical assistance for lower Columbia River treaty tribes -- Yakama, Umatilla, Nez Perce and Warm Springs.

Martin charted December's precipitation at 55 percent of normal in Portland. Hood River December totals were 40 percent of normal, while tribal lands also fell short -- Umatilla (35 percent), Nez Perce (60 percent), Warm Springs (45 percent), and Yakama (50 percent of normal).

Martin, who surveys ocean conditions, cites warm surface waters in the south Pacific that have shifted northward along the western Pacific as a potential cause of the aberrant Northwest weather pattern. Those apparent ocean temperature "departures" from the norm may be "tweaking Mother Nature into thinking we're in an El Nino when we're not," Martin said.

"Basically, Alaska and the Yukon are getting our moisture right now," he said. "The weather is pretty classic, but unfortunately we're not squeezing any moisture out of those jet streams."

He warned that the river operators, and TMT, must be especially guarded this year and occurrence similar to last year, when spring flood control drafts left water in short supply when anticipated June runoff did not match expectations. An April meltdown greatly reduced the snowpacks.

In a low water year (last year was near normal) a similar scenario "could be disastrous for fish operations," Martin said.

Link information:
NRCS snowpack summary:
NRCS snowpack updates:
Northwest River Forecast Center:

Barry Espenson
Columbia Basin Starts Year with Low Snowpack
Columbia Basin Bulletin, January 5, 2001

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