MOFFAT COUNTY — Until that moment, the most dominant fauna of the landscape arguably had been butterflies.

Nerves were fluttering in the bellies of the neophyte paddlers who had stopped to scout the Green River's ominously named Hell's Half Mile rapids, getting their first glimpse of the menacing rock known as Lucifer lying mercilessly in its center.

About the same time, someone glanced upward at the towering walls that form Dinosaur National Monument's formidable Canyon of Lodore and noticed three bighorn sheep nimbly picking their way down the steep cliff wall as they headed to the riverbank for a drink. The distraction served as a moment of levity, displacing the metaphoric butterflies as the crew paused to absorb a literal representation of this captivating place complete with some butting of horns.

By both ram and Dinosaur National Monument standards, however, the sparring was minimal. This place, after all, has seen its share of battles, be they the annual rite of rutting rams, audacious early river descents or the legendary launch of modern environmentalism when David Brower and the Sierra Club took on the Bureau of Reclamation's powerful push for a pair of hydroelectric dams on the Green River within the park boundaries back in the mid-1950s.

After flooding Dinosaur with Sierra Club and Wilderness Society members, reporters, film crews and dignitaries, Brower built convincing congressional testimony around the concept that solitude, wildness and risk constitute play for some people. And, such rare recreational opportunities exclusive to places such as the Green and Yampa rivers through Dinosaur National Monument deserve to be preserved.

"There are probably quite a few who would not care to ... see any of the wild backcountry of the parks, who would not care to climb in a rubber boat and float down the rapid and calm stretches of Dinosaur's beautiful canyons," Brower testified. "But, to some people, this very trip has been the finest scenic experience they ever had."

It was in that spirit that U.S. Sen. Michael Bennet of Colorado gathered a group of stakeholders including sportsmen, conservationists, officials from the Department of Interior, water experts and members of the oil and gas industry to join him and his family last week on a two-day float of the Green River as it passes through Colorado in Dinosaur. The 21-mile trip outfitted by Grand Junction-based Adventure Bound River Expeditions (800-423-4668) began at the Gates of Lodore and ended at the Yampa River confluence at Echo Park, site of the defeated Echo Park Dam.

Although the Colorado River Storage Project approved in 1956 stipulates that "no dam or reservoir constructed under the authorization of the Act shall be within any National Park or Monument," the area surrounding Dinosaur remains the subject of public lands policy debates. Those discussions range from questions about mineral leasing and air quality concerns to endangered species issues and some withering water diversion projects. The setting provided an opportunity for a more casual and informal discussion of various public lands and natural resources issues facing the area, the state and the nation.

"You'd have to have an entirely different contextual view of resources and things to think that damming this would be a good idea," Bennet said in a candid exchange with Denver Water CEO Jim Lochhead. "I knew it was beautiful, but I didn't know how beautiful it was. It's spectacular."

It's grand thinking inspired by an even grander environment that takes ideas outside the box and allows them to open and breathe in a 3,000-foot canyon with no ceiling.

"For me, it's just nice to be around people that are not all screaming at each other," Bennet joked.

Indeed, with only about 10,000 annual visitors sharing 300 private and 300 commercial launch permits for 25 people or fewer on both rivers within Dinosaur, a good amount of serenity comes with a float. The majority of that territory, approximately 210,000 acres surrounding the Green and Yampa, will celebrate the 75th anniversary of its proclamation as a national monument by President Franklin D. Roosevelt this Sunday.

The original 80-acre monument set aside by President Woodrow Wilson dates to 1915, six years after Carnegie Museum paleontologist Earl Douglass discovered dinosaur bones at the site. Credit for the first river descent, however, goes all the way back to John Wesley Powell's 1869 exploration of the Green River.

"In 1869, John Wesley Powell came down here trying to figure out how to make his way through this canyon. In 1969, the United States of America put a man on the moon. Can you imagine what that century was like?" Adventure Bound co-owner Tom Kleinschnitz said. "That was a big century, and we're working on that next century. The decisions we make for the next 50 years are going to go forward for 500 years."

"It's the decisions that we're making and the decisions that we're not making that are really important to the next 500 years," Bennet added.

Although the junior senator readily accepts the role of understudy to Sen. Mark Udall as an outdoorsman, Bennet has quickly earned a reputation in Washington for environmental protection and responsible energy development. He recently led efforts to designate Chimney Rock, near Pagosa Springs, as the nation's second newest national monument. He is a strong proponent of renewable energy technologies and has pushed to improve conservation programs in the Farm Bill to conserve scarce water resources.

And, after his inaugural voyage, clearly he's an advocate of the Green River and Dinosaur National Monument.

"I don't think you really can appreciate this place if you've never been here," Bennet said before sluicing an inflatable kayak between the boulders of Hell's Half Mile and drifting by the bighorns on the beach. "You can't imagine it."