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Columbia at a six-year low but trending upward

By Stuart Tomlinson, The Oregonian
Published: September 24, 2015, 9:59pm

PORTLAND — To some extent, low water levels on the Columbia River are a seasonal reality in late summer and early fall. Most of the snow that fell during the winter has melted, and the region is firmly locked into its dry season. Tides also play a role.

But due to record low snowpacks across the Columbia River basin last winter, and widespread drought in Oregon, Washington, Idaho, Montana and into Canada, hydrologists at the Northwest River Forecast Center in Portland last week predicted the river’s level in Portland would be at its lowest in 15 years.

But by early this week, the assessment was scaled back to a six-year low

“It’s not looking like it’s going to be that dramatic,” river forecaster Andy Bryant said. “Although, these next couple of mornings it will be pretty low.”

Bryant said the amplitude of the tides — the difference between low and high tide during the tidal cycle — is typically when the river reaches its lowest level.

The forecast center measures how much water is flowing through the river by picking a point near the river bed and using that as a reference for how high or low the water level is — the point is considered “zero.”

On Tuesday at high tide, the river was just 2 feet above that zero point. But it was expected to rise to 4 feet on Wednesday and continue to trend upward, to nearly 4.5 feet by Oct. 1.

Until then, Bryant said, places where boaters used to ride well above the river bottom may not be even able to navigate some stretches of the river. Underwater obstacles — old pilings, rocks and debris — also will be more visible or hiding just below the surface.

The forecast center predictions are passed to the U.S. Coast Guard, which has an obvious role in making sure commercial river traffic can transit up and down river, and that recreational boaters know which areas to avoid.

The low water alerts are also broadcast on National Oceanic and Atmospheric Administration Weather Radio, a somewhat limited audience, as well as to the Multnomah County Sheriff’s River Patrol, Bryant said.

Lt. Travis Gullberg of the Multnomah County river patrol, said he and his fellow deputies usually don’t issue low-water warnings until late August and September.

“This year, we were giving the warnings in July because the river was so low even then,” he said. “The water was lower sooner.”

Gullberg said his office has seen an uptick in reports of people who beached their boats purposefully, and then get out to have lunch on an island beach, only to return to find their boat “high and dry” and unable to get back because the tide went out. Even with low water, the difference between high and low tide can be 4 feet.

Bryant said most houseboats on the river should be fine because most marinas dredge to ensure houseboats are sitting on the bottom.

The good news for recreational boaters, Bryant said, is that the Bonneville Power Administration usually releases more water during weekends when demand for electricity is lower. The BPA is required to release enough water to ensure the river remains navigable.

“It’s a very complicated system that has to be balanced between recreation, fish and wildlife, river traffic and power generation,” said Kevin Wingert, a Bonneville Power Administration spokesman.

Wingert said in September and October of 2001 and again during the same period in 2009, flows out of Bonneville Dam bottomed out at 80,000 cubic feet per second. The average flow this September is 95,000 cfs.

“At BPA we have excellent forecasters on staff who proactively monitor and model weather, river flows and basin conditions throughout the year,” Wingert said. “This enables us to plan and be prepared to deal with a variety of different scenarios, including our current dry year operations. We have no concerns at the present about meeting our customer’s load.”

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