Objections from Front Range cities are forcing state officials to make a last-minute overhaul of Colorado’s water plan and pledge to build new reservoirs that enable population growth.

Aurora, Colorado Springs, Denver and Northern Colorado Water Conservancy District providers also are demanding that the state detail plans for the diversion of more water across mountains to the Front Range.

That puts them at odds with Western Slope residents, who Tuesday weighed in with their own demand that Gov. John Hickenlooper block diversion of more water.

The Colorado Water Plan, 30 months in the making, spells out how the state intends to supply water for the 10 million people projected to live in the state by 2050. Hickenlooper has ordered the Colorado Water Conservation Board to complete the plan by Dec. 10.

Colorado Springs lambasted it as “guardrails without a road” — a list of what Colorado must not do — and said it was biased against cities and failed to direct action to meet growing needs.

Springs utilities officials issued a 14-page critique demanding corrections to secure city support, asserting that “one or more new transmountain diversions will ultimately need to be constructed to address Colorado’s water-supply gap.” The plan “should include an affirmative statement that it is state policy to develop additional storage.”

Front Range cities already divert about 163 billion gallons a year from the west side of the Continental Divide. The diversions deplete waterways, including the Colorado River, increasingly coveted by 40 million people.

The state’s chief planner said in a Denver Post interview that 46 staffers are scrambling to fix the plan and include a massive new commitment for new reservoir storage of 130 billion gallons.

That’s equal to what planners propose to gain from city water-saving, such as less watering of lawns.

But there’s still no consensus over where water to fill new reservoirs would come from to meet a projected 2050 annual shortfall of 163 billion gallons.

Aurora shares some of Colorado Springs’ concerns about lining up sufficient supplies and storage, Aurora Water director Marshall Brown said. It also is disappointed the plan emphasizes urban conservation when agriculture uses 85 percent of water statewide, Brown said.

“We’re still committed to making progress on conservation, but that progress isn’t going to be enough to solve the water deficit,” he said.

The Northern Colorado Water Conservancy District also urged state planners to make changes, contending increased diversion from the Western Slope “has got to be on the table,” spokesman Brian Werner said. New reservoirs are essential, he said.

Denver Water manager Jim Lochhead favored “a more specific action plan” from the state, adding that Denver is optimistic a final plan will help meet water challenges.

Meanwhile, 1,500 western Colorado residents petitioned Hickenlooper, opposing more siphoning to Front Range cities and suburbs.

“That water’s our livelihood. Our ranchers use it. Farmers use it. We use it for recreation, tourism,” said Silt Mayor Bryan Fleming. “We stand together. We cannot afford to lose any more water on this side of the mountains. We understand they have water issues, but we need to come to a comprehensive plan with conservation. We need to watch building, and developers should have to secure water before building.”

A Colorado Water Plan lacking support from Front Range cities and suburbs, where 80 percent of the state’s 5.3 million people live, could be hard to implement, forcing state lawmakers to try to manage water scarcity.

Colorado Water Conservation Board director James Eklund said he’s aware of Front Range cities’ objections and acknowledged the current plan contains no target for increased reservoir storage.

“We’re going to correct that,” he said. “We’re going to add a storage goal, a measurable objective.”

Ensuring new storage space to hold 130 billion gallons would address “a huge chunk of the gap” between water expected to be available and expanded demands, Eklund said.

The final plan will offer general principles for diverting water — such as addressing environmental needs — but won’t commit to a specific diversion project.

Front Range leaders “know that we’re not just going to come out and write the Colorado Springs or Denver water plan. They get that,” Eklund said. “For something statewide like this, we’ve got to make sure we’re striking a balance so that this is really, truly Colorado’s water plan.”

Bruce Finley: 303-954-1700, bfinley@denverpost.com or @finleybruce