It began four years ago as a lawsuit over water levels in White Bear Lake, a recreational jewel of the Twin Cities suburbs. But the ruling that emerged in a Ramsey County courtroom this month could have sweeping implications for water use across all of Minnesota, forcing the state to impose limits on everything from suburban sprawl to crop irrigation.

In a sharp rebuke to the Minnesota Department of Natural Resources, Judge Margaret Marrinan said the state has failed to protect White Bear Lake from excessive groundwater pumping and ordered the agency to limit water use in the surrounding communities. The state, she ruled, has a broad duty to protect the lake and the groundwater as a public trust — in essence recognizing that despite being one of the most water-rich states in the nation, Minnesota doesn’t have an endless supply.

Conservationists and environmental lawyers say the ruling, if it stands, has implications for sectors as diverse as manufacturing, agriculture, mining and drinking water across the state.

“This is new,” said Alexandra Klass, who teaches environmental law at the University of Minnesota. “We are used to having as much water as we want.”

And while environmentalists see it as a critical victory for the lakes, rare fens, wetlands and rivers that the state is obligated to protect, the decision will intensify what are already fractious political fights over Minnesota’s water.

“The whole issue of water policy is in play,” said Sen. Chuck Wiger, co-chair of the Minnesota Legislative Commission on Water, whose district includes White Bear Lake. It’s possible, he said, that the Legislature will try to weaken or rewrite the strong environmental laws that underpin Marrinan’s ruling.

“I imagine we are going to see some pre-emptive strikes,” he said.

DNR officials haven’t said whether they plan to appeal the decision, but in a statement last week, they sharply disagreed with the judge’s findings.

“It’s fair to say there would be far less ground- and surface-water use permitted, ” if Marrinan’s ruling became the statewide standard, Barbara Naramore, DNR assistant commissioner, said in an e-mailed response to questions. Had the ruling been in place for the last decade, she said, “there would have been a complete residential watering ban” affecting some 500,000 residents in White Bear Lake and surrounding communities.

Naramore also said the ruling would reach “beyond what is needed to ensure water sustainability.” For example, she said, the judge’s order could halt any construction within 5 miles of White Bear Lake that requires groundwater use.

Local governments are already nervous.

“One thing we know is that it makes things really uncertain,” said Bryan Bear, city administrator in Hugo, a growing suburb north of White Bear Lake. “We have no idea what someone might do with this.”

Aquifer under stress

The 2013 lawsuit was filed by local residents and supporters around White Bear Lake, a St. Paul summertime landmark for decades. They sued after the lake shrank before their eyes, leaving docks and boats high and dry. In 2013, it dropped as low as 919 feet above sea level, then recovered to 923 feet, but only after recent heavy rainfalls.

The real long-term problem, they said, is excessive demand for groundwater by the growing and thirsty communities around the lake, coupled with the DNR’s reluctance to deny permits for large-volume pumping, which was draining an aquifer that sustains the lake and supplies many surrounding communities.

The judge’s decision hinged on a scientific study conducted by the U.S. Geological Survey and additional research by the DNR, which found the lake was exceptionally dependent on groundwater — specifically, the aquifer that lies beneath it. When pumping pulled out more groundwater than rainfall could replenish, the lake shrank.

In a strongly worded 140-page ruling, Marrinan said the DNR violated state environmental law by permitting excessive groundwater pumping. “This practice is not sustainable,” she wrote, “and is an unreasonable and irresponsible approach to managing groundwater.”

Taking the argument a step further, she said the state must consider the cumulative effects of groundwater use, and can’t issue permits when “it does not know the effect of its permitting actions.”

It was one of the few decisions in Minnesota that also invoked what is known as the public trust doctrine, the deeper legal obligation of state and federal governments to protect natural resources. “By failing to properly regulate the extraction of groundwater, the DNR was placing at risk the ability to use the surface water,” said Byron Starns, a former Minnesota deputy attorney general.

During the three-week trial in March and in response to questions this week, the DNR officials disputed that. The judge, Naramore said, seemed to use “very different standards” for scientific certainty and what represents harm to aquifers and surface water.

Nonetheless, if the decision compels the DNR to change its approach to groundwater, the implications are profound, said Naramore and several environmental advocates.

“What the judge did was give DNR a backbone,” said Rep. Jean Wagenius, DFL-Minneapolis, who’s made water issues a priority during her years at the Legislature. “It’s a real win for future generations.”

But in a state where 75 percent of the citizens get their water from the ground, where agricultural irrigation is exploding, and economic development in both urban and rural areas also depend on water, the implications are unnerving, say others.

“We do have concerns,” said Perry Aasness, executive director of the Minnesota AgriGrowth Council, the lobbying arm for the state’s biggest agricultural and food companies. “Water availability varies widely” across the state, he said, and he worries that the DNR would adopt a one-size-fits-all approach to permitting. “These decisions are best handled locally,” he said.

Agricultural irrigation, which the DNR manages through water permits, is already a divisive issue across the state. The DNR has identified 16 “areas of concern,” which show signs that groundwater is under stress. They include the Straight River near Park Rapids, which has been affected by an explosion of irrigation for potatoes and other crops that grow in the sandy soils. The same is true of Little Rock Creek near St. Cloud and the Bonanza Valley north of Willmar.

Other major industries are not immune. In Hibbing, the city and a taconite company asked the DNR to intervene to resolve a dispute over draining a mine pit that affected the city’s drinking water supply; and in suburban Washington County, the water demand from growing communities has affected nearby trout streams.

Lawn watering limits?

The DNR has plans for managing and measuring groundwater use in some of those areas, including the Straight River and Bonanza Valley. Others are being developed.

Naramore said the agency’s research in those areas has already resulted in restricting permits, but Marrinan’s decision raises questions about whether the DNR is doing enough, fast enough. White Bear Lake, for example, lies within one of the DNR’s “areas of concern” and already has a water management plan. Yet the judge said that the agency has not followed that plan by requiring restrictions on lawn watering or by setting maximum withdrawal levels.

Naramore said the DNR is making progress on White Bear Lake, and has almost completed a model to manage groundwater use in the area. “We understand that people often wish agencies would move faster on complex management issues,” she said. “But it is equally important for those actions to be based on sound science and appropriate community engagement.”

By placing a priority on natural resource protection, Marrinan’s ruling could reach beyond groundwater use, and apply to water pollution and drinking water protection, which are managed by other state agencies.

Naramore and attorneys specializing in natural resource law said it could — and environmental advocates said they fervently hope it will.

“This is telling them they have to stand up for the resources because no one else will, and that is their job,” said Steve Morse, executive director of the Minnesota Environmental Partnership, which lobbies for more than 80 environmental groups in the state. “It’s a clear precedent.”