One of Minnesota's largest farming operations has sued the White Earth Band of Chippewa after the tribe sought to regulate its water use on its reservation and surrounding land.

In a move that could shape tribal treaty rights and water use across the state, the tribe started requiring anyone who pumps more than 10,000 gallons of water a day or more than 1 million gallons a year on its reservation or within 5 miles of it to get a tribal permit. That would be in addition to any permits that heavy water users need from the state.

But only the state can regulate the water use of non-tribal members, argued R.D. Offutt Farms, a potato producer that owns or operates about 50 farms with high capacity irrigation wells in and near the reservation. R.D. Offutt has asked the court to throw out the band's permit, saying the costs and uncertainty in getting approved could force farms to shut down.

"This will have a profound impact not just on our farms, but on the farms of our neighbors, our team members, our suppliers, our customers who have already purchased the crop, and our communities who rely on the stability of the regional agricultural economy," R.D. Offutt spokeswoman Jennifer Maleitzke said in a statement.

Farmers need clarity from the courts about water permitting in Minnesota, Maleitzke said.

"We believe — and the evidence supports — the state should be regulating water use throughout Minnesota," she said.

Minnesota is in the grip of a water crisis, White Earth Chair Michael Fairbanks said in a statement.

"The White Earth Nation is dedicated to using sound science for a fair and balanced review of water resources, ensuring equitable decisions while safeguarding the health and welfare of everyone within the Nation's boundaries," he said.

The case was filed early this month in U.S. District Court in Minnesota; no hearings have yet been set.

White Earth enacted the water permit requirement on the heels of explosive growth in irrigation in the state and region. The reservation occupies about 1,000 square miles in northwestern Minnesota, just west of Itasca State Park at the headwaters of the Mississippi River. Its borders cover Mahnomen County and parts of Becker and Clearwater counties.

Irrigation in the area has more than doubled since the late 1980s, from 3.5 billion gallons of water a year to more than 8 billion gallons, according the Minnesota Department of Natural Resources. That extra water use does not seem to have had much effect on nearby surface waters, the agency said in a recently released report of the Straight River area.

But more intensive modeling and studies would be needed to measure whether some of the wells closest to the Straight River are reducing stream flows during the driest times of the year when irrigation is at its highest, the report said.

Regulators with Gov. Tim Walz's administration said they will watch how the case plays out in federal court.

"We understand that the Band's action has raised many questions and concerns for farmers and other landowners in and near the White Earth Reservation," Minnesota Department of Natural Resource officials said in a statement. "However, whether the Band has the legal authority to require non-band members to obtain a Band water appropriation permit when they are appropriating water on private property within or outside the boundaries of the Reservation is a question of Federal law."

Under federal law, White Earth can regulate non-members if their actions threaten the security and subsistence of the tribe, band lawyers argued when creating the permit requirement.

The cumulative impacts of high-capacity irrigation wells pose "significant threats" to the health, welfare and subsistence of the tribe, the tribe's governing body wrote.

To get a tribal permit, farmers would need to pay a $5,000 application fee. The review process could take three years and the band would impose usage limits and inspect wells.

The state charges farmers $140 a year to pump up to 50 million gallons of water. All usage is self-reported and the state didn't fine any of the roughly 800 farmers who broke their permits and pumped a total of 6.5 billion gallons more than they were allowed during the 2021 drought.

R.D. Offutt is one of the largest potato growing operations in the world. It rapidly expanded in Minnesota in the past two decades, becoming one of the state's biggest water users.

By 2018, the company's growth concerned state water regulators to the point that they stopped approving its well permit applications. The Department of Natural Resources said a comprehensive study was needed to find out whether increased water use was drying up lakes and streams or degrading water quality in wells in the region.

Rather than fund the study, the company reached a deal with the DNR that withdrew all but five permit applications. The DNR asked lawmakers to fund the study. They did not, and it was never done.

The company operated 47 permitted irrigation wells drawing roughly 25 million gallons each within the reservation and its 5-mile buffer in 2022, the latest year data is available. Those wells drew a total of 1.1 billion gallons of water that year, according to state usage reports.