Colorado is expected to add 3 million residents by 2050, a 56 percent increase in a state already facing water supply challenges. To keep pace, the state is embarking on its biggest era of water development in generations.

At least seven major new reservoirs and water diversion projects are being planned in Colorado, which had a population of 5.6 million in 2017. Many would continue the controversial practice of diverting water across the Rocky Mountains from the state’s Western Slope, where the majority of Colorado’s precipitation falls, to its more arid Front Range, where people are flocking to Denver, Boulder, Fort Collins, Longmont and increasingly sprawling suburbs.

The water projects have been inspired partly by the Colorado Water Plan, an effort by Governor John Hickenlooper to solve a projected water deficit of 560,000 acre-feet by 2050, or enough to serve more than 1 million households. The plan calls for 400,000 acre-feet of new water storage and an equal amount of water conservation.

The plan is only two years old. But critics say it has prioritized gray infrastructure – new dams, pipelines and pumps – over green projects like water conservation and sustainable land use.

“Every single city is trying to further drain a river and refuses to do aggressive water conservation,” said Gary Wockner, director of Save the Colorado, an environmental group working to protect the Colorado River from further water extractions. “These cities and these water agencies think they have a water right, and they want to get that water no matter what. They want to secure all the water they possibly can.”

The water grab, as Wockner sees it, is a significant concern because climate change is already shrinking the Colorado River’s flow. One recent study found flows have already declined by an amount equal to Colorado’s projected water deficit, and will continue shrinking as the climate warms into the future. This year, the Colorado River watershed is experiencing one of its driest winters ever.

The state water plan does not recommend any specific water development projects. But Hickenlooper has personally endorsed several of them. He also appointed all the voting members of the Colorado Water Conservation Board, the entity that oversees the Water Plan and awards grants for water projects.

Greg Johnson, chief of water supply planning at the Water Conservation Board, said the state’s plan emphasizes conservation just as much as new water supply projects. But he said the latter may be more more pressing in some cases.

“Some of the bigger projects that are in permitting right now are helping meet really critical supply needs that a lot of those faster-growing northern Front Range suburbs have, where they’ve got new developments going up all over the place,” Johnson said. “They have maybe a 10- or 15-year horizon to get some of those things done.”

One of the water developments endorsed by the governor won a $90 million loan in 2017 from the Water Conservation Board – the largest loan in the board’s history. Known as the Windy Gap Firming Project, it proposes a new reservoir called the Chimney Hollow Reservoir near Longmont to store Colorado River water diverted through an existing tunnel under the Continental Divide.

The loan covers nearly one-fourth of total costs for the project, which is proposed by the Northern Colorado Water Conservancy District.

As its name implies, the project is intended to “firm up” existing Colorado River water rights held by a dozen Front Range cities. The cities already draw on these water rights, but can’t fully tap them in some years because of storage limitations. The new 90,000 acre-foot reservoir will solve this problem and allow them to divert the river almost every year.

The project would result in diverting 30,000 acre-feet more water out of the Colorado River every year than is currently diverted.

As a result, Wockner’s group recently filed suit against the United States Bureau of Reclamation and Army Corps of Engineers for granting permits for the project alleging, among other things, that they violated federal law by failing to consider adequate alternatives. WildEarth Guardians, Living Rivers and Waterkeeper Alliance are coplaintiffs in the case.

Other major projects in the works include the Moffat Collection System, a plan by Denver Water to expand Gross Reservoir to hold 77,000 acre-feet of additional diversions from Colorado River headwaters streams; and the White River Storage Project, a proposal for a new reservoir of up to 90,000 acre-feet in the northwest corner of the state, near the town of Rangely.

Wockner argues that aggressive water conservation could keep up with Colorado’s growth.

“There’s considerable disagreement about whether they need new water for population growth,” Wockner said. “Even if the growth may need new water, there are also disagreements about how to get it. They can conserve more water, they can do better growth management so towns and cities aren’t just creating more and more lawns.”

He noted that among all the communities that would benefit from the water projects currently proposed on the Front Range, only Fort Collins has a program that pays customers to take out lawns in favor of less-thirsty landscaping.

Greg Silkensen, a spokesman for the Northern Colorado Water Conservancy District, said the Windy Gap project is vital to many fast-growing Front Range communities that have lower-priority water rights.

“The Colorado economy is just crazy. Everybody and their brother is moving here,” Silkensen said. “There is a great deal of environmental mitigation that will go forward if the project is built. There’s going to be a lot of benefit to the Upper Colorado River if it does go through.”

Those projects include stream habitat restoration in the Colorado River and water quality improvements in Grand Lake, part of the existing Western Slope diversion system.

Building new dams and the associated environmental mitigation is very expensive. But soaring water prices – driven by the state’s growth boom – make such projects a lot more feasible.

Consider another water development proposal: the Flaming Gorge Pipeline. It calls for diverting 55,000 acre-feet of water from the Green River in Utah’s far northeast corner. The water would be routed into a new 375-mile pipeline arcing north into Wyoming, then south into Colorado as far as Douglas County, a fast-growing suburb south of Denver.

The project was dismissed by the Federal Energy Regulatory Commission in 2012, when it involved diverting five times more water. Now the original developer, Aaron Million of Water Horse Resources, is trying again with a pared-down proposal estimated to cost around $900 million.

The economics work, Million said, because the market price of water for urban use in Colorado has tripled since 2012. Also, he believes the Trump administration will view the project more favorably.

“Between the past administration and the current administration, the regulatory environment has changed dramatically,” he said. “We’re looking at all possibilities for storing the water up and down the Front Range.”