Kuhn's office bookshelf holds several ink-stained, broken-spined old government publications, and, his report makes clear, they stand as a useful metaphor for the broader history of the river. They are essentially a series of warnings that came at the wrong time.

In 1924, just two years after the Colorado Compact was signed, a government hydrologist calculated that the actual flow of the river was 10 percent less than the Compact negotiators had assumed. In 1965, a water engineer named Royce Tipton estimated that the river's reliable flow was really about 14 percent less. "That was pretty shocking at the time," Kuhn says. It only got worse: Subsequent reports found that long-term flows were fully 22 percent less. "But then we just kind of put those reports on the table and went back to saying there's a lot of water.

"About the time the Tipton report was done, things turned wet. And they stayed wet through the late '90s," he says. "That wet period was the beginning of the Rocky Mountain boom days. That's when our growth exploded in the West."

The wet cycle meant there was more than enough water to accommodate the growth spurt, at least for the next 35 years. It also caused a weird psychological drift for water managers. Although severe droughts had left their mark hundreds of years back in the paleologic record, the 20th century was abnormally wet. Consequently, what we think of as normal is, in fact, unnaturally wet, compared to the much longer lifetime of the Colorado River.

Throw in climate change, which will almost certainly result in a decrease in average flows for the Colorado River (though to what extent is still hotly contested), and things really start looking grim. The desert Southwest is facing the slow decay of the water supply upon which the region has been built.

"An 80 percent year is not that bad. But if we had 20 years of 80 percent runoff on the Colorado River, we'd drain Lake Mead and Lake Powell," Kuhn says. "We're so close between supply and demand that a long period of 80- or 85-percent years will bankrupt the system."

Kuhn's quest to understand the river put him at the front of a sometimes lonely fight to challenge the conventional wisdom in Colorado. Some saw his argument as a self-interested effort to keep the Front Range from stealing the Western Slope's water, by arguing that there wasn't any water left to take. But during the summer of 2007, Kuhn's conclusions were validated in a surprising way.

Several Western Slope communities sued Denver to prevent the city from securing new rights to Colorado River water. They argued, basically, that there simply wasn't enough water in the river.

Glenn Porzak was the lawyer who argued against Denver in the case. And, as it happened, he had seen a copy of Kuhn's report. "(Kuhn) sent it out to a number of people, saying, ‘Give me your comments,' " says Porzak. "I read this thing and said, ‘I'll give you my comment: I want you as a witness in this case.' "