High Runoff Prompts Flooding, Power Concerns

According to NOAA's Northwest River Forecast Center's official June forecast, the April to August runoff at the Dalles Dam is now 126 MAF, or 135 percent of the 30-year (1971-2001) average. That's a lot of water set to flow through the Columbia River system.

While not a record, it's close to the 61-year record of 147 percent, and it's already begun to present problems for the region's power system. The combination of too much hydro generation coinciding with high winds (often at night when demand is low) has meant that the Bonneville Power Administration has had to take wind offline at times.

Episodes of over supply sometimes occur during the spring run-off, and when that happens, Bonneville can spill water rather than directing it through turbines to generate electricity. But only to a point. Passing water through the spill gates creates gas bubbles that can hurt fish, and there are legal limits on dissolved gas levels.

Council members were briefed by the Bonneville Power Administration on the power supply and spill situation at a meeting last week.

Concerns about flooding are also growing, with western Montana and the northern panhandle of Idaho hit the hardest with high flows and flooding. The U.S. Army Corps of Engineers is responsible for regulating the major storage reservoirs in the U.S. and British Columbia for flood control.

"Both Libby and Hungry Horse dams are currently on a controlled flood control-refill operation to protect areas immediately downstream, such as Bonner's Ferry and Columbia Falls, and to help provide system flood control protection for the Portland-Vancouver areas," says Jim Ruff, manager, mainstem passage and river operations.

"This is one of those years when we should be thankful we have these major storage projects to provide the region with flood control," he added. "Otherwise, we'd have major flooding throughout the basin!"