Arrowrock Dam

Tom Michael / Boise State Public Radio

It’s Mid-May, I’m at the Boise airport, hopping in a Cessna with pilot Don Reiman and Kevin Lewis, the director of Idaho Rivers United. We’re going to “fly the flood,” to see what the swollen rivers and reservoirs look like from the air, especially along the Boise and Big Wood rivers.

There has been months of flooding on Idaho rivers, with a reservoir system that’s been straining at capacity, as the deep winter snowpack has slowly melted off. Now, in the second half of June, the floodwaters are receding.

Don sketches out the flight path.

WaterArchives / Flickr Creative Commons

The Army Corps of Engineers Wednesday told the Idaho Department of Water Resources it could not recommend raising the height of Arrowrock Dam on the Boise River. The announcement was a disappointment to the state and the Corps.

The water resources board thought raising the height of the hundred-year-old dam would be the best way to reduce flood risk and increase water storage in the Treasure Valley. So it commissioned the Army Corps to study it. After a seven-year study costing nearly $3 million, the Corps agreed.

WaterArchives.org / Flickr

Arrowrock Dam is celebrating its 100th birthday this year. “It was a monumental effort,” says Kelsey Doncaster. He’s been studying the dam as a historian with the Bureau of Reclamation Columbia Cascades area office in Yakima, Washington.

He says it’s a marvel of engineering that keeps irrigation canals in the Treasure Valley full, while controlling flooding of the Boise River.