Power managers divert flow to reservoirs, slow plant output and give power away
By Ted Sickinger
Winter’s snow drought has given way to a temporary flood of late-spring runoff, forcing regional managers of the electrical grid to give away power, dial back generation at thermal plants and rapidly fill reservoirs to maintain acceptable conditions for migrating fish.
Robust water flows in the region’s rivers are typically a blessing, creating a bounty for electricity generation, irrigation, fish passage and recreation. Indeed, only a month ago, the Bonneville Power Administration was issuing dire warnings about summer water shortages.
Those shortages are likely to materialize regardless, as rain now won’t substitute for snowmelt in July and August. But early June’s onslaught of moisture has temporarily pushed the Columbia River and its tributaries toward flood stage and taxed the hydro system’s flexibility to manage competing interests.
The prevailing pineapple express has pushed precipitation levels to 700 percent of normal in some areas of the Snake River Basin and 170 to 200 percent of normal on the upper Willamette River, said Jim Barton, chief of water management in the Columbia Basin for the U.S. Army Corps of Engineers.
Too much rain means too much water over the dams’ spillways, and the resulting turbulence leads to excess dissolved oxygen in the water. That’s harmful to fish, so the big dam operators in the region –the Corps and Bureau of Reclamation –divert as much water as possible into reservoirs or through the dams’ turbines to generate electricity.
“All the reservoirs are filling or near full, so that makes it challenging,” Barton said. “You can only store so much.”
Then you generate.
“The more the dams can generate, the less they spill and the less issue with dissolved oxygen,” Barton said.
When you create electricity, however, you need to use it, immediately, or risk an imbalance on the grid.
During the past few days, the 31 federally operated hydroelectric dams in the region have been running full tilt, generating an average of 13,000 megawatts of electricity. That’s 144 percent of their normal spring generation –the equivalent of adding four nuclear plants worth of electricity generation to the regional mix.
Complicating the picture is the region’s growing fleet of wind turbines, which have been cranking out extra megawatts as the same storm cells dumping rain into the rivers have whipped wind speeds higher.
“You can only run the turbines as fast as you can find a home for the power,” said Michael Milstein, a spokesman for the Bonneville Power Administration. BPA markets the power from the federal dams and one nuclear plant, and integrates the spiky output of the region’s wind fleet onto the grid.
To accommodate the surge, the federal nuclear plant at Hanford has been dialed back to 25 percent of capacity, Milstein said. BPA also has warned wind farm operators that it won’t be accepting much, if any, unscheduled power production.
Meanwhile, the agency has been enticing utilities to turn off their own power plants by giving away electricity for free, or near free, at several junctures since Wednesday.
“That’s helpful to customers, as it flows through in lower power costs,” said Steve Corson, a spokesman for Portland General Electric.
While the weekend weather is expected to be dry, it takes several days for a slug of moisture to move through the system.
“We expect things to be returning to normal by Monday,” Milstein said. “It certainly has been a test of the system.”