Whether their tone was defensive or simply reassuring, Colorado Compact supporters felt compelled to speak up for a system that is being tested as never before. The worst drought in 100 years has placed unprecedented strains on water users in both the upper and lower parts of the Colorado River Basin. Planners are now on a crisis footing, and reduced allocations are in the offing. The real hunkering down may be yet to come.

Critics call the compact, and particularly a reservoir system anchored by Lake Powell and Lake Mead, an anachronism, a relic of wetter, headier times that has been overtaken by the West's rapid urban growth.

But without the compact, which allocates 15 million acre-feet of water annually among Utah, Wyoming, Colorado, New Mexico, Nevada, Arizona and Colorado - plus 1.5 million acre-feet for Mexico - advocates argue that the current situation could be a lot more dire than it is.

"During this early 21st century drought, this system has continued to provide resources," Colorado Supreme Court Justice Gregory Hobbs told members of the Colorado River Water Users Association. "Even with severely ranging characteristics, in high-flow years and low-flow years, it has worked. And it has proven vital."

The current drought, now in its sixth year, "is our wake-up call in the Colorado River Basin," acknowledged Steven Griles, deputy secretary of the Interior. "But there are lots of signs that the [compact] states will meet the challenge."

Colorado River Compact detractors call such talk wishful thinking. The template has changed, they say. And water officials have been slow to adjust to what they call a new reality for the Colorado and its water storage assets.

David Haskell, policy director for the environmental group Living Rivers, believes the original compact was signed and allocations made under incorrect assumptions. Tree-ring science, he says, now shows that the 1900s was one of the wettest centuries on record, and that the 1980s - when Lake Powell was filled - was the wettest decade in that wet century. As a result, the compact states have been living large, artificially.

"Saying the compact is working is like sitting in a room full of food and never being hungry," Haskell said. "But now they're down to their last few hamburgers and everything is changing.

"What we've got now is a whole lot of demand and less supply," he added. "It worked up until now because it was an extremely wet century and the '80s was an extremely wet decade. Were it not for that decade, Lake Powell would never have been more than half-full. It would be empty now. What you've seen is a system that has been working under very beneficial circumstances."

Water officials beg to differ. The compact states have weathered the drought very well, they say. And regardless of history, a Lake Powell now 130 feet below capacity is still providing users with both power and water. The compact system predicted periods of drought and shortage. The system is working exactly as it was intended to.

If anything, compact state participants say they are getting better at their jobs, and they cite a number of recent developments as evidence:

l A landmark deal struck last week in which Arizona agreed to sell Nevada 1.25 million acre-feet of its share of Colorado River water for $330 million over the next 15 years.

l California's commitment two years ago to live within its annual 4.4 million acre-feet allotment of Colorado water.

l An adaptive management plan for Glen Canyon that calls for the removal of non-native fish species, such as trout, while at the same time rehabilitating native species, such as the Humpback Chub.

l Last month's experimental test flow at Glen Canyon, designed to return sediment to the Grand Canyon, restoring beaches and creating backwater habitat for native fish species.

"In the last four years we've seen some remarkable practices," said undersecretary Griles.

But again, compact critics, such as Haskell, wonder which century Western water officials are living in.

"The question now is, how do we plan for the future now that we know what kind of water deliveries are likely?" he said, citing projections that show a future average annual allotment of 13.5 million acre-feet - or 3 million less than is allocated now, when one includes Mexico's annual share of Colorado water.

Living Rivers, like the Glen Canyon Institute and other environmental groups, is calling for the decommissioning of Glen Canyon, moving a portion of that water into the more efficient Lake Mead and using underground aquifers - as Arizona does now - to bank the rest.

"We've got far more underground storage capacity than storage capacity in the Colorado River system," said Haskell. "Powell has outlived its utility and become a liability. You can't deny that Lake Powell hasn't delivered during the drought, but that's really the wrong question. It's not a sustainable system."

But that has been, and continues to be a catastrophic alternative to Western water officials, who consider Powell and Mead the linchpins of the entire Colorado River Basin. Pulling the plug on Powell would invite economic disaster, they say.

"These dams were built to fluctuate," said Colorado justice Hobbs. "The reality is, without the Colorado River Compact, our water storage problems would be much worse than they are right now."

jbaird@sltrib.com