PORTLAND, Ore. (KOIN) – You may want to budget some more cash for gas this season, because, according to AAA, Oregon fuel prices are on the rise.

Several reasons typically contribute to the rise in gas prices on the West Coast this time of year – including the coast’s distance from oil, the annual switch to summer-blend fuel, and regional-specific environmental programs – but one cause that directly impacts the Pacific Northwest may not be what you’d expect: The Columbia River.

According to a weekly report from the American Automobile Association, current increases in Oregon’s gas prices have been “amplified” by the closure of the river’s locks, which prevents fuel barges from coming through.

Just last week, Oregon’s average rose to $3.86 per gallon – nine cents more than the week before and 49 cents more than the current national average sitting at $3.37. AAA says the state has the 20th largest week-over-week gain for a state in the nation.

Typically, the entire West Coast sees a jump in prices due to maintenance and a switch to summer-blend fuel between April and June. According to the Environmental Protection Agency, switching fuel during the warmer months of the year, when gasoline can more easily evaporate, helps reduce air pollution.

“Things have settled down a little since last week, when the Oregon average for regular had the biggest weekly jump in the nation. But drivers can expect rising prices for the next several weeks due to the temporary decrease in supplies,” Marie Dodds, the public affairs director for AAA in Oregon, said.

Most Oregon counties have averages below $4 per gallon, with the exception of $4.17 in Curry, $4.02 in Harney, and $4.4) in Multnomah. But there is hope in sight: Work on the Columbia River is expected to wrap up by the end of March.