Laurel Morales/KJZZ

Thirty seven million people rely on Colorado River water. Lake Powell is at 56% capacity, up from 38% last year thanks to snowpack.

Environmentalists filed a lawsuit Tuesday against the federal government alleging it has to take climate science seriously when it comes to managing Glen Canyon Dam.

The lawsuit alleged the federal government "knowingly, willfully and illegally ignored established climate science" in its 20-year management plan. Instead the Bureau of Reclamation has relied on what they call "historic" inflow data.

"If they have to use the science that's in their own report, they have to consider an alternative that includes decommissioning the dam because there literally won't be enough water to keep the turbines at Glen Canyon Dam spinning to create hydropower," said Gary Wockner, executive director of Save the Colorado, the lead plaintiff in the suit.

The lawsuit called for the agency to follow National Environmental Policy Act guidelines and to present a full range of alternatives, including a plan to tear down Glen Canyon Dam.