Agricultural dry-up is an ominous phrase, but it's reality on the Front Range as farmers sell off water rights to satisfy unquenchable urban sprawl.

It won't be enough. Population predictions show Colorado doubling to 10 million in 50 years, mostly occurring on the Front Range. Experts with the Colorado Water Conservation Board say current water supply comes up short.

The question is how to keep farming viable while covering a Front Range domestic supply gap expected to be between 350,000 and 500,000 acre-feet per year?

The state's eight water basins are negotiating solutions that will culminate in a Colorado Water Plan for future management due out late next year.

Front Range metro suppliers say the solution is diverting more water from Western Slope rivers and reservoirs via the 22 transmountain diversions already in place.

But state water districts west of the Continental Divide are calling foul, and have calculated that if Front Range residents stop watering their thirsty Kentucky Bluegrass lawns it will be enough to make up the supply shortage.

"Ninety percent of domestic water use - your kitchen, bathroom, showers - makes it back to the river systems and reservoirs through return flows. It has less water-supply impact than watering lawns, which absorb 70-80 percent of it," said Mike Preston, general manager for the Dolores Water Conservation District.

Preston is also chairman of the Southwest Water Roundtable, tasked with forming a local strategy for responsible water use and policy.

"The state proposes a 60-40 standard for domestic water consumption, 60 percent for in-home and 40 percent for outdoor lawns to better conserve water for ag production and population growth," he said "But we're getting a lot of pushback from Front Range water suppliers who are accustomed to the 50-50 ratio now."

For domestic water obtained via transmountain diversions, the suggested ratio is 70 percent indoor use, and 30 percent outdoor use.

Furthermore, increasing transmountain diversions have far-reaching consequences. Siphoning off more Western Slope water to the Front Range threatens the state's water-contract obligations for downstream states like Arizona, Nevada and California who depend on Colorado River basin water stored in Lake Powell and Lake Mead.

"They're watching our water polices, more than we look at theirs," Preston said. "Colorado is the headwaters for a lot of their supply."

Meanwhile Western Slope water - especially the Blue Mesa Reservoir complex, near Gunnison, and Wyoming's Flaming Gorge Reservoir - are looked at with envious eyes by Front Range water districts.

But the massive reservoirs are mainly designed to store water for contractual delivery to Lake Powell and Lake Mead relied on by Lower Basin states.

Colorado is entitled to 51 percent of Colorado River basin water above Lees Ferry, Ariz. Once it is diverted to the Front Range, it is lost to the Colorado River system, eventually draining east toward the Mississippi River.

To make a dent in unsustainable water demand in Fort Collins, Denver, and Colorado Springs, they should become more like Las Vegas, local water officials say.

The city's successful lawn conservation program has vastly reduced water consumption, and includes strict drought-resistant landscaping regulations for future development.

Colorado passed legislation this summer to try and regulate lawn-watering, but it came up short, critics say. SB17 originally required that future residential development using water from agricultural dry-up could only have lots with 15 percent of irrigated landscaping. But the requirement was dropped in favor of "best practices" language.

"The rewrite was to study it further," said water engineer Steve Harris. "At every meeting, we lament ag-dry up. The original bill was saying the next five million people can't use water like the previous five million people."

Tree-ring data shows the Colorado River at Lees Ferry suffered a 60-year drought between 1200 and 1300, causing mass migrations. Water officials report this region has suffered a 15-year dry period, a troubling trend that needs attention.

"Front Range water district plans all include transmountain diversion as the solution," Preston said. "We're saying it won't be considered until you get more aggressive about domestic conservation by limiting outdoor watering."

More education is needed about the importance of responsible water management, said Bruce Whitehead, of the Southwest Water Conservation District.

"Many people don't have a clue about the state water plan or the issues we're facing," he said. "We have a lot of work to do in our basin to educate the constituency."

For more information go to www.coloradowaterplan.org.

jmimiaga@cortezjournal.com