It was never a great secret that the limits of Colorado's water allocation have been gradually closing in. But Kuhn's emperor-has-no-clothes pronouncements have nonetheless come at considerable cost to the state's self-respect.

His findings mean, first, that reliable water supplies for each additional bit of growth are becoming increasingly uncertain. Second, they call into question the viability of at least two proposals to divert water to the Front Range: One that would draw as much as 300,000 acre-feet of water from the Yampa River, a tributary of the Colorado; and another, floated by an entrepreneur named Aaron Million, that would pump roughly 250,000 acre-feet from the Green River, itself a Colorado tributary. Kuhn's findings also suggest that there's little water left for the predicted explosion of oil shale development in western Colorado, which could require up to 400,000 acre-feet per year. It's anybody's guess when, or whether, oil shale will go forward, but large energy companies like Shell have already filed claims for hundreds of thousands of acre-feet of water.

All of that raises the prospect that growth -- or at least growth with a dependable water supply -- may soon be finished in Colorado. And that's not a message that has been well received.

For roughly the past decade, Scott Balcomb was Colorado's lead representative in negotiations with the six other states that use the river. His task was, basically, to protect the state's water allocation from its rivals. "If we voluntarily decide that we're limited to x acre-feet in our development, and we want to be very safe, we're almost inevitably going to leave water on the table that we could develop," he says. "And I don't like that very much."

In fact, the issue is so sensitive that when Randy Seaholm testified at the Denver water trial in 2007, a state assistant attorney general accompanied him to intervene if he said anything that might compromise Colorado's negotiating position against the other states. Why the attorney general's office didn't move to have Seaholm's water-availability estimates put under seal is not clear. Balcomb, for his part, says that if the state publicly acknowledges that it has only 150,000 acre-feet left -- which it essentially did in the trial -- that number will boomerang back against Colorado in some future fight between the states over the river's last remaining water.

The Colorado River Compact is essentially a contract between the seven states, and its terms were consciously crafted to enable a kind of mutual coexistence. If legal rights to the river had simply been apportioned following Western custom -- the hallowed doctrine of "prior appropriation," which grants rights to whoever first uses the water -- early-blooming California could have laid claim to a large portion of the river's water in 1922.

As part of the Compact bargain, then, Colorado and the other Upper Basin states -- Utah, Wyoming and New Mexico -- managed to reserve 7.5 million acre-feet for themselves. That gave them certainty that their share of the river wouldn't be gobbled up by California before they needed it. But the price of that certainty was a deal that gives the Lower Basin a significant advantage when times get tight.

That proviso says -- stick with this for a moment -- that the Upper Basin states "will not cause the flow of the river at Lee Ferry" -- the dividing line between the two basins -- "to be depleted below an aggregate of 75,000,000 acre-feet for any period of ten consecutive years." Put differently, that means the Upper Basin will do nothing to prevent the flow of 7.5 million acre-feet downstream to the Lower Basin each year. (As Compact aficionados will rush to point out, the precise terms of the clause dictate that the amount be calculated as a running average of 75 million acre-feet over 10 years -- or "75 over 10," in Compact-ese.)

The problem, of course, is that the Compact promises more than the river can deliver. The Lower Basin gets 7.5 million acre-feet of water from the river's mainstem; the Upper Basin gets its 7.5 million acre-feet; and Mexico gets 1.5 million acre-feet, for a total of 16.5 million acre-feet. But over the long run, the river's mainstem can probably only reliably deliver about 13.5 million acre-feet. In 1986, that mismatch caused John Carlson, then special counsel to the River District, to write, "Unfortunately, the mathematics of the law of the river simply have not worked: The sum of the parts is greater than the whole."