Thirst for solutions: concerns rise with South Metro's growth.

• Author: Best, Allen

By almost any definition, Castle Rock is a boomtown. Population, now at 35,000, has doubled in just the last five years--startling when you consider the sputtering of the nation's economy and the tech-stock meltdown. At every curve and corner, though, Castle Rock has the new-car smell of a Cadillac showroom. Houses are cavernous, their exteriors neatly adorned, lawns and gardens carefully primped: the good life, Colorado style, Sunset Magazine writ large upon the land. And don't for a moment think the party is anywhere near over. Giant yellow, mechanical ants still push new loads of dirt around as the covenant-controlled Meadows community prepares for more pastel-colored houses. Castle Rock is marching rapidly toward a build-out population triple that of today. It's a town with undaunted ambition.

And the foundation for its new prosperity? Although Castle Rock residents would never think of themselves as such, they are in a sense miners, cresting the latest wave in Colorado's long history of boom-and-bust mining cycles. From the Pikes Peak gold rush of 1858 to the most recent oil-shale bust of 1982, the pattern is by now familiar. But Castle Rock's mining boom is different. What is being mined in Castle Rock and other communities between Denver and Colorado Springs and stretching eastward onto the Great Plains is water. Drinkable, life-giving water. Information technology or financial services may deliver the paychecks of many of the residents of Castle Rock, but homes and businesses need water, and that water is mostly coming from taps into underground aquifers that were created during glacial periods many, many years in the past.

The paradox of this richly expanding settlement is that these underground reservoirs are even now playing out. Slowly, but now steadily, it's becoming more and more difficult to extract water from these giant beds of sand lying hundreds and thousands of feet underground. While Castle Rock does not expect to have problems meeting peak demands for 50 years, the costs associated with delivering that water are expected to rise dramatically even as the town phases in alternative water sources.

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And those alternatives themselves will not be cheap. They may, for instance, include buying farms from Fort Lupton to Greeley, from Fort Morgan to Sterling, for their water rights--and in some cases pumping the water back to South Metro. Another alternative is to draw water from Colorado's Western Slope, where very few water rights actually remain for the taking in the state's most accessible headwaters. Mitigation costs to Western Slope counties for taking that water also will probably be high, and the actual cost of pushing water through pipes across several mountain ranges is likely to be even more expensive for individual water consumers.

But those may be the choices for future residents of Castle Rock. The wells the town draws water from now may never be enough.

And Castle Rock is not alone. Its unfolding water drama is shared by other growing communities spread across the wonderfully rolling, oak-brush and pine-tree studded hills of Douglas, Arapahoe and El Paso counties. Indeed, it's the central water story of Colorado. At issue is how will this great sprawl of communities from Parker to Monument and beyond--ironically, Colorado's most affluent, best educated, and most politically conservative population--be provided water to drink in the years ahead? What will happen to these boomtowns when the water mines play out? "I think we are building toward a great crisis," longtime water lawyer Greg Hobbes, now a Colorado Supreme Court Justice, said at a recent lecture in Denver. "We can't afford to let South Metro fall off the map." From Aurora to Colorado Springs, those areas with the least secure water supplies have been growing the most rapidly. The headliner has been Douglas County, which includes Parker, Castle Rock and Highlands Ranch, among others. Since 1960, the population has been doubling and tripling every decade, leading the nation during the 1990s in rate of population growth. And still the rush continues. Five years ago, the population was 176,000, now it's at 251,500.

Castle Rock's water situation also is neither the best nor the worst in the South Metro area. One water district, which serves the affluent Roxborough Park neighborhood, has no water supplies assured beyond 2023. Another, growing Aurora, uses little well water, but does rely on water transported from the north, south and west while aggressively buying farm water from the South Platte and Arkansas River valleys. Parker is on the brink of a record year for issuing water taps, and is building Reuter-Hess Reservoir, now planned at half the size of Cherry Creek Reservoir, but with the potential to quadruple its size in order to serve other water-short jurisdictions, including Castle Rock. Lone Tree is on a much more brisk building pace now than it was before the drought or the 2001 recession. Building of single-family homes in unincorporated parts of Douglas County may have slowed down some, but condominiums, town homes and commercial development has continued apace.

If consumers, homebuilders and local governments are worried about water supplies for those developments evaporating, it isn't evident in their plans. With some exceptions, much of that population will depend upon aquifers in what is called the Denver Basin, a swath of territory at times 50 miles wide that features several layered...