EDIT
So Kuhn took the stand on June 13, and carefully noted that "there's no single answer to how much water Colorado has left to develop. The answer is a function of how much risk the water users in Colorado are willing to take." But, he testified, the amount of water that the state can reliably count on is no more than 150,000 acre-feet -- considerably less than half of what would be needed for the 2.9 million people projected to arrive over the next quarter century. Denver Water's attorney, Casey Funk, opened his cross-examination by remarking, "Boy, that's a pretty pessimistic view of the future, Mr. Kuhn. Does the state of Colorado share that same opinion?"
As a matter of fact, the state of Colorado did share that opinion, although that wouldn't become clear until 13 days later. On June 26, Denver Water called its own witness: a man named Randy Seaholm, who is the state's chief of water supply protection. Funk walked Seaholm through the process of calculating how much water remained available for development. Based on what might be termed a constructionist reading of the Colorado River Compact, that number works out to roughly 1.5 million acre-feet. Still, most water managers recognize that the numbers on which the Compact is based are at least somewhat higher than the river itself can reliably deliver. So Funk took Seaholm through a second set of calculations, this one based on a recent "hydrologic determination" by the federal government.
"And that would leave, then, an amount of around 600,000 acre-feet left to develop under the Compact, based upon that determination?" Funk asked. "Correct," answered Seaholm. Still, that wasn't bad. It's enough for about 4.8 million people.
Just before the hearing, however, Glenn Porzak secured a copy of an internal document, prepared by Seaholm only eight days earlier. The document showed that, at the time of the trial, Colorado actually had only 474,000 acre-feet of water left to develop. More importantly, it showed that once existing and approved projects were built and operating at full capacity -- which, according to the document, will be next year -- only 159,000 acre-feet of water will be left. The number almost exactly matched Eric Kuhn's, and it is only about one-tenth of what the state had officially been saying was available. "Denver led him through the state mantra: ‘OK, on paper, we've got this amount, and we're never gonna admit anything to the contrary,' " Porzak says. "And then it turns out there's this internal document that's just unbelievably close to Eric Kuhn's number. "I've been practicing 35 years," he added, "and I've had some good moments. But it was the closest thing I've ever had to a Perry Mason moment."
EDIT
http://www.hcn.org/issues/41.4/how-low-will-it-go/article_view?src=feat&b_start:int=0