The U.S. Army Corps of Engineers has tightened its management protocol for Libby Dam in northwest Montana.
The change comes six months after widespread flooding downstream from the dam near Bonners Ferry, Idaho. The corps said the flooding might have been avoided had the dam been operated in strict accordance with a program known as variable discharge.
Some residents living near the river and local government officials, however, want the corps to abandon the program entirely and revert to more conservative dam management operations.
The variable discharge program attempts to control flooding while also mimicking the Kootenai River’s ancient flow patterns. This means storing more water behind the dam in winter to provide higher river flows when threatened and endangered fish spawn in spring.
Although the variable flow system was adopted by the corps in 2003 – at the urging of federal and state biologists – it was never strictly implemented, according to a report issued by the corps after the June flood. The flooding occurred when record rain and snowmelt had to be spilled over the top of the dam.
Cindy Henriksen, chief of the corps’ reservoir control center in Portland, said strict adherence to variable flow protocols will mean “less guesswork” for dam operators, but potentially less water in the reservoir during the dry months of summer.
“Since we’re adhering to (discharge) guidance without flexibility, that may mean Libby Dam may not refill,” Henriksen said. This could also mean less water is sent downstream in July and August for salmon and steelhead in the Lower Columbia, she said.
Bill Michalk, a farmer and licensed engineer whose land was flooded in June, believes the corps is abandoning its flexible approach to flow management to protect itself from lawsuits. The agency is facing a lawsuit from environmental groups that accuse the corps of violating the Endangered Species Act.
Environmentalists contend both fish and farms can be protected as long as the corps strictly follows the variable flow protocols.
But Michalk wants the corps to drop the variable flow program entirely and go back to the days when less water was kept in the reservoir during winter and spring months. Variable flow, he said, depends too much on long-range weather forecasts.
“Long-range forecasting is highly inaccurate,” he said. “That puts us at a higher risk of flooding. They’ve reduced the margin of safety.”
The corps has adopted the strict variable flow program only for 2007. More analysis needs to be done before a long-term system is implemented, Henriksen said, adding that the Libby Dam is the “most challenging” dam to operate in the Columbia River basin.
Although an estimated $10 million in damage was caused by the flooding, had Libby Dam not been in place, the cost could have been as high as $45 million from all the rain and snowmelt, according to a 16-page report issued by the corps on Friday.