A settlement in a lawsuit over White Bear Lake's plummeting ­levels has set in motion plans to divert water from the Mississippi River, a fix that could top $623 million and push 13 northeast metro communities to cut water consumption.

The hard-fought deal was announced Monday between two groups that mainly represent homeowners around the lake and the state Department of Natural Resources (DNR). The settlement, subject to a judge's approval, would suspend the litigation, which began in 2012, for three years.

During that time frame, the DNR has agreed to support plans to divert water from the Mississippi River to supply six communities — ­Shoreview, Vadnais Heights, White Bear Lake, White Bear Township, Mahtomedi and North St. Paul — and take pressure off the Prairie du Chien/Jordan aquifer, the vast underground reservoir from which those cities and scores of others across the Midwest draw their water. Seven other cities would eventually be added to the new system.

Last June, the Metropolitan Council, which has been studying water supply issues across the region, estimated the cost for those projects to be $155.4 million. It would soar to $623.2 million when all 13 communities are brought on line. The Legislature is expected to be presented with those proposals next month and determine how they would be funded.

The settlement does not compel either the DNR or the Legislature to build that water diversion system, nor would it force communities to switch their water source. But it puts the legal process on hold so that those plans can play out.

The settlement also requires the DNR to get the 13 communities to adopt water conservation measures with the goal of reducing consumption by 17 percent, based on an eight-year average.

The city of White Bear Lake has started an aggressive campaign to get residents to be more mindful of saving water. Measures include using low-flow toilets, reducing lawn watering, capturing stormwater for irrigation and recycling "greywater" from hand-wash basins, showers and baths for other uses, such as flushing toilets. New plumbing codes for those communities also could help conserve water.

The other major component is an agreement by the DNR to set a "protective lake elevation" for White Bear Lake by next Nov. 1.

White Bear Lake has lost about one-fourth of its volume over the past decade, and parties in the suit remain in disagreement over the cause. The lake's water level, typically about 925 feet above sea level, plummeted to an all-time recorded low in January 2013 with a surface elevation of just under 919 feet. Heavy rains last summer temporarily pushed up levels, but they have since receded, and could fall even more.

The DNR could take steps, such as ordering water pumping to be stopped, or withholding pumping permits, if it determines that decisions aimed at protecting the lake elevation actually lower the lake level.

Though the two groups that sued the DNR — the White Bear Lake Restoration Association and the White Bear Lake Homeowners' Association — and the state agency still dispute key aspects of the lawsuit, all sides on Monday hailed the settlement as a constructive compromise.

"This is a historic, significant settlement, and we're very pleased with it," said Katie Crosby Lehmann, one of the attorneys for the Restoration Association. The homeowners "stepped up and made a difference. They stepped up to protect our most precious resource: water."

The homeowners were not seeking damages from the DNR, but only compelling the agency to take steps to save the lake. Crosby Lehmann's law firm, Robins, Kaplan, Miller & Ciresi, donated its legal fees, but the homeowners groups had to raise money to pay for studies by water experts.

"This is a win-win for everyone," Crosby Lehmann said.

Shannon Whitaker, a board member of the Homeowners Association, pointed out that the Metropolitan Council itself has been sounding the alarm about pressure on aquifers from suburban development, and that water usage rates are not sustainable in the long term. "White Bear Lake is kind of a canary in the coal mine — it's a signal of things to come," she said.

At the core of the lawsuit is an assertion by the homeowners groups that the DNR issued too many well permits to northeast metro communities, drawing too much water from the fragile lake and allowing levels to be sucked down through its porous bottom. Studies by both the U.S. Geological Survey and the Metropolitan Council have made that link.

The agency still disputes that position, said Barb Naramore, assistant DNR commissioner. The lake's historically fluctuating levels are important to its ecology, she said. She added that the DNR's own hydrology expert has concluded that the lake's decline is likely climate-related.

Still, Naramore said the settlement affirms much of what the DNR has already been doing to protect the lake and water resources in the northeast metro.

"We feel this agreement is in the best interests of all the parties," Naramore said. "And it's consistent with the principles of sound water policy."