PORTLAND, Ore. — The Willamette River is now considered one of the most endangered rivers in the country, according to conservation organization American Rivers.

The group ranked the Willamette as the fifth-most endangered river in the nation.

The group says 13 flood control and hydropower dams along the Willamette's tributaries have been blocking the natural migration of both juvenile and adult salmon, and steelhead for decades.

As a result, fish numbers in the Willamette have dropped dramatically.

More: Fish recovery plan could drain Detroit Lake for 2 years

More: Feds sued for declining fish runs in Willamette watershed

"What used to be tens of thousands of fish in the case of Winter Steelhead down to just a few thousand," pointed out Travis Williams, executive director of Willamette Riverkeeper. 

RELATED: Killing sea lions is saving endangered steelhead, biologists say

The group agrees that the dams are important for reducing floods and providing power. But it also thinks the U.S. Army Corps of Engineers needs to do a better job at making them more "fish-friendly."

"While we've seen a lot of improvements in the Willamette for public health, for boating and swimming, the challenge we're faced with this year is whether or not we're going to allow an iconic species salmon and steelhead in the upper Willamette to go extinct," said Dave Moryc, senior director for American Rivers.

The U.S. Army Corps of Engineers estimates the dams have prevented approximately $1 billion in flood damage per year on average since 1994.

But, the agency said it is working to improve the fish passage problem. The Corps has spent more the $230 million to date on improvements. It said it needs more federal funding to complete the jobs.

But getting that money may not be easy. The Trump administration just proposed a more than 50 percent cut in the amount of money the Corps will get to do those improvements projects.

Oregon's congressional delegation is now asking for that money back.