Tapped out: Front Range thirst exacts toll at every turn.

• Author: Best, Allen

Many years during May, I have paused along small mountain streams to see, hear and feel the giant gush of spring runoff. The experience is one of the world's great pleasures. Standing on the banks of the Colorado River as it churns through Gore Canyon, or on the Eagle River as it teems through Minturn, or even Clear Creek as it swells through Wheat Ridge, I am always transfixed by the wondrous sight of water, so recently ice and snow, rushing to join the oceans from whence it came. Even now, 10 and 20 years after the fact, I can recall these scenes as if they happened yesterday.

Yet I wonder how many yesterdays I have left.

Some years ago, I tracked the Eagle River to its source. The stream passes Minturn, an old railroad town, and upstream passes through picturesque Red Cliff, a former mining town that is just now getting some fresh paint.

Above Red Cliff and Camp Hale, where in 1942 the Army put the Eagle River into a ditch to allow room for the 10th Mountain Division to train, the Eagle turns glittery again. Continuing on a dirt road, I at last parked my pickup at a wondrous waterfall, and followed the headwater up a steep hillside. Imagine my surprise.

The stream's course here was entirely artificial. To avoid contamination by the Climax Molybdenum Mine, this babyish river had been diverted to a new course altogether, one that produced the striking waterfall. Even at its source, little about the Eagle River is natural, and the stream serves well as a metaphor for water all across Colorado. Farmers and ranchers are selling water, not cattle and vegetables, to city dwellers; water that naturally flows west is pumped east, drying up whole streams and rivers; huge subdivisions are being planned for hundreds of thousands of people who really won't know when they move in how long they might have water to drink.

Which is not to say Colorado has no need for holding back, diverting and ultimately marshalling the state's water resources into new and life-giving purposes. From at least the time of the Ancestral Pueblo, who corralled rainstorms and melting snow in small reservoirs at Mesa Verde, people in Colorado have been doing just that. During the last 150 years, engineering has harnessed water in ways that have been ever more magnificent. Ditches incised into the contours of hillsides that deliver water from rivers to distant fields of grass, alfalfa and corn, are amazing. More stunning yet are the tubes, tunnels and assorted other methods used to convey water from the Western Slope, where 75 percent of Colorado's precipitation falls, mostly as snow, to Eastern Colorado, where about 80 percent of the state's residents live.

Yet for all the impressiveness achieved by hydrological tinkering, there's also a loss for this oasis state. Water delivered to my house in suburban Denver, allowing me to nurture a small garden of peppers, cabbage and other vegetables, diminishes the flow of creeks near Winter Park and other mountain valleys. My own, singular impact is slight, but it has to be considered in concert with the 3.6 million people living elsewhere along the Front Range.

In listening to people talk about Colorado during the 21st century, I often have heard simple answers for water problems: The Western Slope should simply cease its stubbornness and share its water; more storage must be built; or cities should stop growing. None of these answers ultimately satisfies as a solution.

Tradeoffs must be found. Ultimately, water will be available for growth, but not for every business and home, and not without losing some of what Colorado has been.

NO TIME FOR FARMING

The largest of the brush-stroke solutions to Colorado's water supply problems in the decades ahead will be conversion of water from farms to municipal uses. This will happen from Grand Junction to Durango, but most poignantly along the urbanized Front Range, where an additional 1 million residents are expected by the year 2025. This conversion from agriculture to residential will be done easily in places like the fringes of Greeley, Loveland and Fort Collins. As farmland is covered with houses, water that previously grew alfalfa will instead grow grass.

In metropolitan Denver, however, the water equation becomes more difficult to write. Aurora, for example, has 300,000 residents, with 500,000 projected by the year 2035. In-fill development will account for a third of this population growth, with the remainder occurring on the short-grass prairie near E-470. As such, water must be imported. This importation already has been occurring for 30 years or more. Much of South Park, the area around Fairplay, was once a place of big haystacks. No more. Denver and Aurora have purchased most of the water there, leaving South Park to go to seed. Similarly, Aurora in the 1970s began buying farmland east of Pueblo, in the area of Sugar City, leaving the land to grow only that which the normal rainfall will allow. That isn't much.

To avoid the stigma of drying up the Arkansas Valley as Los Angeles once dried up California's Owens Valley, Aurora has been structuring deals with farmers near Rocky Ford and La Junta that aim to extract water from farms without destroying the farm communities. One technique, recently approved by the legislature, is to lease water to be used during drought years.

Other Front Range cities are moving down the Platte River.

In 2001, Parker Water and Sanitation District purchased several thousand acres of farms downstream from Sterling. Water from those farms will be used to...