For more than a decade, the federal government spent $700 million on habitat improvements in the Columbia River Basin.

Experts say it's likely the largest, most intensive, and most expensive habitat restoration program in the nation. It's the centerpiece in a federal management plan to relieve the damage that dams cause to salmon and steelhead.

The plan has been litigated in court for two decades; its latest version has also been challenged, with a hearing scheduled Tuesday.

Critics say relying heavily on habitat improvements is not enough to restore wild fish runs. Some advocate breaching dams. Others say spilling more water would help fish.

Officials say record salmon runs show habitat restoration is helping. But scientists say sometimes restoring habitat doesn't work as well as it should.