Kuhn was born on July 4, 1950, in Edmonton, Alberta, where his father was working as a petroleum geologist for Texaco. When Kuhn was 8, his family moved to Flagstaff, Ariz.

Kuhn's grandfather, who lived in Prescott, would often fly up in his Piper Cub -- a tail-dragger without a radio -- and take Kuhn flying over the Grand Canyon and the Indian country of northern Arizona. "In those days," Kuhn says, "you didn't need a pilot's license. All you needed was an airfield."

Kuhn's dad flew, too -- he had been a Marine pilot in World War II -- and for a while, Kuhn seemed set to carry on the family's aviating tradition. He went to the University of New Mexico on a naval ROTC scholarship, where he got his pilot's license. But his vision wasn't good enough to meet the Navy's requirements, and so Kuhn, who graduated in 1971 with an engineering degree, went into the submarine service instead.

In late 1972, Kuhn found himself aboard a submarine called the Halibut as it steamed under the Golden Gate Bridge and then dove deep beneath the Pacific -- headed for the Kamchatka Peninsula on the easternmost edge of Siberia. Kuhn found himself wondering, "What have I gotten into?"

The Halibut carried a contingent of operatives from the National Security Agency, and it slowly crept into the Sea of Okhotsk, where the Soviets conducted many of their ballistic missile tests. There, in 28.6-degree water 500 feet below the surface, the Halibut deployed a dive team. Breathing helium to counteract the intense pressure, kept alive by hot water continuously pumped through their dive suits and working in pitch black, the divers located a Soviet underwater communications cable. Then they wiretapped it.

That mission and several others would yield crucial information about the Soviets' ballistic missile-testing program, helping the Navy maintain its edge in a spiraling arms race between the Soviets' nuclear-armed "boomers" and the American attack subs designed to destroy them before they could vaporize the U.S. But the voyages were so secret that it would be 20 years before Kuhn finally told his family exactly what he had done aboard the Halibut.

After his discharge from the Navy in 1978, Kuhn got a graduate degree at Pepperdine and went to work for the engineering giant Bechtel, starting up the Palo Verde nuclear power plant near Phoenix and the San Onofre nuclear plant outside San Diego. But he didn't stay long: Three Mile Island melted down in 1979, and "the handwriting was on the wall," he says. "No one was building any new power plants."

An ad in the Wall Street Journal, for an engineering position at the River District, led him to Colorado.

Kuhn arrived at the River District in 1981 with no particular expertise in water but filled with his trademark curiosity. "It looked like an adventure to me," he recalls.

From the start, Kuhn immersed himself in the river's convoluted history, and as he worked his way up the ladder (he became general manager in 1996), his curiosity intensified. Then that curiosity became a professional imperative.

In 1999, the drought set in. In 2002, the river's flow was just 25 percent of average. And by 2004, Lake Powell and Lake Mead -- the main backup supply for water in the Colorado River -- were half-empty.

Sometime late in 2006, Kuhn embarked on an exhaustive review of the literature to understand how much water the river could reliably deliver. He estimates that he spent almost 25 hours a week over the next seven months, reading some 10,000 to 15,000 pages.

Kuhn pored over reports from the river's earliest explorers, congressional testimony and comprehensive plans for development, pleadings from court cases, and an avalanche of scientific papers about El Nino, tree-ring chronologies, climate change and obscure phenomena like the Atlantic Multi-Decadal Oscillation and shifts in the onset of spring runoff. Along the way, he became one of a handful of people who have developed a true connoisseur's delight in the exegetical nuances of the 1922 Colorado River Compact and its reams of related documents and scholarly analysis.

He gradually synthesized what he had learned into a 111-page report. Much of it he wrote out longhand, making reference along the way to Deuteronomy, the modified Blaney-Criddle methodology for determining the consumptive water use of pasture grasses, and The Incredible Shrinking Man. "When he was writing, it was constant. He would come home and write till he went to bed," says Sue Kuhn. "He was really excited about the whole thing. He was thrilled."