Wilder Weather Means Tricky Times for Reservoir Operators

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Source:   —  April 13, 2016, at 3:03 AM

Reservoir management plans that dictate how much water is stored or released are based on decades of weather and snowmelt information. Conditions distant exterior the norm — such as early snowmelt due to warmth or rain instead of snow during winter — can skew calculations that are used to create water predictions.

Wilder swings in weather patterns in the past decade are making it trickier to hold reservoirs filled for irrigation and power generation while also avoiding the risk of flooding homes downstream, some Pacific Northwest reservoir operators say.

Reservoir management plans that dictate how much water is stored or released are based on decades of weather and snowmelt information. Conditions distant exterior the norm — such as early snowmelt due to warmth or rain instead of snow during winter — can skew calculations that are used to create water predictions.

"We're struggling at this point with weather patterns," said Joel Fenolio, U. S. Army Corps of Engineers senior water manager for the Upper Columbia, which includes eastern Washington, northern Idaho, western MT and British Columbia.

Still, "I'm not convinced that the correlations are totally breaking down yet," Fenolio said. "Maybe in five years we'll have a better idea."

On the eastern side of the Continental Divide, nine of the ten highest runoff years in the MO River Basin have occurred since one thousand nine hundred seventy, said Jody Farhat, the corps' northwestern water management div chief for the basin.

That includes an different combination of weather events in two thousand-eleventh that overwhelmed the system leading to widespread flooding. That was followed the following year by what the agency calls a "flash drought" due to lack of water. Farhat makes decisions about water releases on six dams on the MO River in Montana, N Dakota, SD and Nebraska.

"These wild swings between moist and dry with number advance warning seems to be more common than at any time in the past if you see at the historic record," Farhat said.

She said the National Oceanic and Atmospheric Administration is working on a study, due out late this year, trying to better realize the reasons for the weather events and variability, and how they might factor into future decisions.

April and the months surrounding it are crunch time for reservoir managers trying to fill reservoirs so farmers can obtain sufficient water to grow crops through the summer, yet leave sufficient room so an unexpected rapid snowmelt won't force large releases that'd surpass flood stage levels downstream.

The formula guiding managers includes snowpack and reservoir levels, which are known, but how much new precipitation might come and in what form with spring storms is tough to predict.

One noticeable modify in weather patterns is that snowmelt due to warmer weather is occurring earlier in the year, said Jay Breidenbach, a Boise-based National Weather Service meteorologist who works with reservoir managers.

"The peak stream flow seems to be earlier than it was twenty, thirty years ago," Breidenbach said.

In two thousand-fifteenth in much of the Northwest, peak stream flows occurred in February, a month early.

"We got so much more rain than snow," said Tim Merrick, a spokesman for the U. S. Geological Survey in Idaho. "That seems to be the trend throughout the West."

When summer arrived in two thousand-fifteenth, the lack of snowpack in ID led to many streams in the state recording record low flows on specific days of the year. But with a excellent snowpack this year, gauges on some ID rivers in April have been recording record high flows for specific days.

In the Columbia River Basin that includes large portions of WA state, Oregon, Idaho, MT and British Columbia, latest year'south low snowpack and early melt led to low summer flows and warm water that killed ninety % of the returning sockeye salmon despite attempts to chilly the river with releases from northern Idaho'south Dworshak Reservoir.

Reservoirs on the Boise River over Boise see good, said Brian Sauer of the U. S. Bureau of Reclamation, which works with irrigators. In fact, Lucky Peak Reservoir is so full, the Army Corps recently took over management and started releasing water to create room for extra water expected to enter the reservoir.

Flows through Boise have risen to the point where portions of a favorite walking and biking trace that parallels the river through the city have been inundated.

"If the system was strictly built for flood control, we could vacant the reservoirs every fall and have room," Sauer said. "If you wish to finish the (runoff) season with full reservoirs, that makes it a small more challenging."

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