Colorado has a difficult water problem. Eighty percent of its water is on the Western Slope, but 80 percent of its population is on the Front Range.

Adding to the problem are estimates that Colorado's population will increase from 5 million to 10 million by 2050, the majority of which will live on the Front Range.

Then there is the persistent drought, diminishing snowpack, and legal obligations to deliver Colorado River water to Lake Powell and lower basin states.

To tackle the issues and come up with conservation measures, Colorado has been holding meetings the past year in the state's seven river basins.

Recently in Mancos, the Southwest Basin Water Roundtable met with 30 local residents about the plan.

Front Range water demand was a central topic. The Front Range's water supply is augmented by 500,000 acre-feet per year of transmountain diversions from the Western Slope. (For comparison, McPhee Reservoir holds 380,000 acre feet.)

"The model we have now is not sustainable, so we're here to find solutions," said Ann Oliver, roundtable moderator.

The concern is that as urban areas grow, unallocated water from Gunnison's Blue Mesa Reservoir and Flaming Gorge reservoir will be drawn into the transmountain tunnels to meet demand.

That could put pressure on other basins to meet water and power obligations to lower basin states fed by Lake Powell and Lake Mead. Many say failure to control the situation threatens Western Slope agriculture.

"We depend on the water to grow the food, and the Front Range depends on us to put dinner on the table," said one farmer.

The state is flirting with conservation mandates to save water, but has run into stiff political resistance from water districts in Denver, said roundtable chairman Mike Preston.

A recent bill by state Sen. Ellen Roberts, a Durango Republican, would have put water restrictions on the lawns for new Front Range housing development. But the bill was stripped of its teeth in the legislative process.

"It's a Front Range-Western Slope standoff," Preston said. "The bill would have been effective, but Denver water is saying they don't need it."

Another proposal is to adjust the 60/40 water-use model on residential development to a conservation-minded 70/30 model by 2030. The strategy divides residential water use this way: 70 percent for indoor use and 30 percent for lawn and garden.

Reducing outdoor water use on lawns and gardens is seen as a solution because plants consume water, whereas household water is eventually flushed and drained back into the watershed beyond the sewer treatment plants.

The proposed 70/30 rule for new development would also help offset the "buy and dry" trend currently happening on the Front Range.

"When municipalities buy up agricultural water for urban growth, that farmland is lost," Preston said.

When Front Range housing developers tap water diverted from the Western Slope, they should be held to a higher water-conservation standard, he added.

J. Paul Brown, Colorado representative-elect, said Front Range water managers need to come up with options.

"The Front Range should develop their own water before thinking about ours," he said.

Drought and diminished water supply have spurred debate. And that's a good thing, said John Porter, president of the Southwest Water Conservation board.

"This plan would not take precedent on water compacts, private water rights, or prior appropriation law," he said. "Rather this process is recognizing we have a problem and need to satisfy the doubling of our population."

Public distaste for mandates on water conservation needs to be overcome, said Sam Carter, of the Dolores River Boating Advocates.

"It is up to the state, cities and counties to try and regulate use," he said. "Why are there not stronger laws for conservation?"

The final Colorado state water plan is due out next year.