Federal officials have reached a settlement with four of five Northwest tribes that would leave hydroelectric dams in the Columbia Basin intact and commit federal agencies to spend $900 million on improving conditions for endangered salmon.

Regional tribes and federal agencies that manage 24 dams and irrigation projects along the Columbia and Snake rivers have been legal adversaries for years over balancing fishing rights, salmon runs and power demands.

Under the settlement announced Monday by the Bonneville Power Administration, the tribes would end lawsuits they have filed against the federal agencies over management of the power-producing system and agree not to file further lawsuits for 10 years.

During that time, the federal agencies would expand their efforts to protect endangered and threatened fish in the Columbia Basin, spending the $900 million for hatchery improvements, stream restoration work, screens to protect fish and additional spillway weirs on some of the dams.

But Oregon's governor strongly criticized the agreement, saying it is premature and the tribes were taking a short-term view.

Its implementation depends on U.S. District Judge James Redden's approval of a scientific plan for protecting fish, called a biological opinion. Redden has rejected previous biological opinions, and has given federal officials until May 5 to present him a new one. The biological opinion will propose detailed solutions for mitigating threats to fish posed by dam operations.

Oregon Gov. Ted Kulongoski said Monday the settlement appears to grant tribal approval of the biological opinion before it is even announced, in exchange for the guarantee of federal funding.

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"It's a sad day for me," Kulongoski said.

Oregon is also in discussions with federal agencies on dam operations.

Environmental and fishing groups also criticized the agreement with the tribes, partly because it would take the possibility of dam-breaching off the table.

"This agreement doesn't change the law, it doesn't change the science," said Todd True, attorney for Earthjustice, representing a number of environmental groups.

"It addresses issues that may be important to the tribes, but it doesn't address the critical issue of river operations," True said.

Environmentalists have argued that salmon populations cannot recover without removing some dams, especially the migration bottleneck to Idaho created by four dams on the lower Snake River. Restoring fish access to the inland mountains may take on added importance if global climate change warms the region.

"What's becoming increasingly urgent and increasingly clear is restoring the Snake River and getting fish back and forth successfully to thousands of miles of healthy, pristine, high-elevation cold spawning streams in central Idaho," True said.

The BPA and the four tribes that announced the settlement hope it will give impetus to resolving disputes that have been raging for years over how to protect endangered and threatened fish in the Columbia and Snake rivers.

The tribes have taken the agency to task for what they felt were inadequate responses to their treaty rights, cultural and religious beliefs that have strong ties to fishing, said John Ogan of the Confederated Tribes of the Warm Springs Reservation.

"There have been improvements and gains secured" in this agreement, Ogan said. "It's a real action plan for fish."

One tribe not party to the agreement, the Nez Perce, said it still wants to see the four lower Snake River dams taken down.

"The dams on the lower Snake River and mainstem Columbia have a significant impact on the fish and on our people," said Samuel Penney, chairman of the Nez Perce. He said the tribe will continue talks with the federal government.

The tribes and federal agencies who signed the agreement say it makes specific commitments to action that haven't been seen in other plans, including more than 200 specific projects across the basin, ranging from fixing degraded streams and riparian areas to putting in screens and irrigation systems that allow agriculture to move forward but protect fish.

"We have spent decades arguing with each other," said Steve Wright, BPA administrator. "Today these parties are saying let's lay down the swords, let's spend more time working collaboratively to implement measures that help fish and less time litigating."

The tribes that signed on to the agreement are the Confederated Tribes of the Umatilla Indian Reservation, the Confederated Tribes of the Warm Springs Reservation, the Confederated Tribes and Bands of the Yamaka Nation and the Confederated Tribes of the Colville Indian Reservation.