SIOUX FALLS, S.D. - A group studying a spring rise on the Missouri River inched toward agreement on several conditions but couldn't come up with recommendations on all issues before Friday's deadline.

The U.S. Army Corps of Engineers is working to meet a directive to protect an endangered fish, the pallid sturgeon.

The idea is to release more water downstream from Gavins Point Dam near Yankton in the spring to mimic a spring rise that would have occurred before the Missouri River dams were built. The thought is that rising river levels will signal the fish to spawn.

The fish's population has decreased since the corps dammed the river about 50 years ago.

The 50-member study group had hoped to come up with a plan outlining conditions of the rise and pass the recommendations to the corps.

The group agreed to several points Friday, including a timeline for the first rise, the rate of the flow and its duration. But talks bogged down late in the afternoon when the group started debate on whether to relax certain flood control measures for farmers in downstream states.

Opponents said they couldn't fully consider the plan because they didn't know enough about it.

Supporters called the defeat of the proposal a missed opportunity for revising river management.

"There will still be a spring rise," said Chad Smith, a spokesman for American Rivers, who suggested the proposal. "But it will happen in a way that is not as good as it could have been."

Gov. Mike Rounds opened the meeting by asking the group to set aside their differences and reach a compromise that would serve all river interests.

States, tribes, farmers and others all have a stake in the decision, Rounds said.

But if the study group can't come up with a recommendation, someone else will, he said - and it may not be to anyone's liking.

Historically, people have been able to reach compromises when confronted by challenges, he said. "If you folks can't do it … can you think of any one who can?"

"The demand on what you're here to do is not going to be easy," the governor said at the start of the group's meeting.

"If it was easy, it would have been done a long time ago."

The U.S. Fish and Wildlife Service has told the corps to enact a spring rise - which involves releasing water from reservoirs into the river.

Corps officials said they have a default plan for a spring rise should the group not make a proposal.

Paul Johnston, a spokesman for the corps' Omaha, Neb., office, said the group's recommendations will be folded into the annual operating plan for the river and also will become part of its Master Manual, the agency's main guideline for managing the Missouri.

Key details of a spring rise include timing and flood control protections for farmers in downstream states, Johnston said.

The corps hopes to have a draft plan ready for public comment by fall and finalize it by the end of the year, he said.

Jim Peterson, a member of the study group, said the diverse interests of stakeholders along the river complicated the committee's work.

"You change one thing here, you change something all up and down the river," said Peterson, of Vermillion. "We're not simply able to satisfy everyone at one time."

Other members said a lack of reliable technical information, a short timeline and prolonged legal and political battles among river states also slowed progress.

Upstream states want more water held in upstream reservoirs, particularly in the spring, to support fish reproduction. Downstream states want more water released from the dams to support barge traffic, city water supplies and other uses.

"There's been 15 years of animosity," said William Beacom, of Sioux City, Iowa, a barge industry supporter.

Also attending Friday's session - the fourth meeting this year - were tribal members, farmers and political representatives.

Raymond Uses The Knife, vice chairman of the Cheyenne River Sioux Tribe, urged the panel to keep future generations in mind as it works toward a recommendation.

River banks have eroded along the Missouri, exposing remains of tribal ancestors buried there, he said.

"This is very important to us," Uses The Knife said. "We want to be able to assert our culture and protect our elders and relatives."