Warm May temperatures are causing more lifts on the Interstate Bridge as water levels reach the highest point in seven years.

Don Hamilton, an Oregon Department of Transportation spokesman, said the Columbia River's water levels at the Interstate 5 bottleneck are nearly three times the average level and approaching flood stage.

"It's been rising up considerably," Hamilton said. Water levels at the bridge are close to 10 feet above average and may rise another foot by the weekend.

Snowmelt is translating to more volume pouring through the Columbia River dams and fast-moving river conditions.

Higher water means more ships, Hamilton said, including "pleasure crafts" like sailboats and other vessels, need a bridge lift to navigate up or down river.

Bridge lifts are prohibited during weekday morning and evening commutes, but anything goes on the weekend. Hamilton said weekend rivergoers called for six lifts Saturday and two Sunday.

Each bridge lift can take 15 to 20 minutes, and more lifts translates to additional delays on I-5.

The transportation agency has seen as many as nine or 10 bridge lifts a day in the past when the river rose to similar levels, and Hamilton said he expects more lifts this weekend.

Hamilton said Oregon and Washington have little choice of when to lift the bridge during the weekend. Federal law gives the right of way to river traffic, aside from weekday mornings from 6:30 to 9 a.m. and during the 2:30 to 6 p.m. commute.

"The river was here first," Hamilton said.

-- Andrew Theen

atheen@oregonian.com

503-294-4026

@andrewtheen