Des Moines Water Works will file a federal suit against three rural counties in northwest Iowa, an action that could trigger far-reaching effects on how states approach water quality regulation.

The action follows a 60-day warning that sparked little promise for solving water quality concerns at Water Works, according to utility trustees. The board voted unanimously during a special meeting Tuesday to file a lawsuit against drainage districts in Buena Vista, Calhoun and Sac counties.

Graham Gillette, chairman of the board of trustees, said since January the public utility hit a wall with local and state leaders, including Gov. Terry Branstad and Secretary of Agriculture Bill Northey.

"Not one responded in any substantive way to the claims we have made in the intent to sue," Gillette said. "Frankly, they did not acknowledge the significant threats faced by those we serve."

Water Works officials and a crowd of supportive residents criticized the state's voluntary nutrient-reduction strategy for farmers. They said it is insufficient for protecting Iowa waterways.

"There is no red water or blue water. There's only dirty water or clean water," Stephen Tews, a resident of Bloomfield, told the board of trustees.

He was one of nearly 20 people who spoke in favor of the lawsuit.

It claims drainage districts act as a conduit, channeling fertilizer and manure between farm fields and waterways. Water Works officials said these districts should be regulated with special permits under the Clean Water Act.

"There's no other business in Iowa that can take a pipe from their business and put it into the surface waters of the state without a permit," Water Works CEO Bill Stowe said. "Agriculture should not continue to benefit from that free drop."

Dustin Vande Hoef, a spokesman for the Iowa Department of Agriculture, said that Des Moines Water Works seemed intent on pursuing a lawsuit in discussions following its Jan. 9 notice of intent to sue.

"They seemed set," Vande Hoef said. "I don't know what we could do in 60 days" that would change the utility's decision.

Northey, who is participating in an international trade trip, and other ag leaders have said the best way to improve water quality is through the Iowa nutrient-reduction strategy.

"Their decision to pull back from collaborative partnerships in the Raccoon River watershed and pursue costly litigation does not appropriately recognize both the complexity of improving water quality and the importance of maintaining a productive agriculture in this state," Northey said.

Gillette listed some steps that might have stopped the lawsuit.

"Regular monitoring and testing of the waterways that allow us to better pinpoint the hot spots, the problems, so we can develop a statewide initiative to address this," he said. "That would (have been) a great starting point."

The nutrient-reduction strategy, approved in 2013, is designed to reduce by 45 percent the nitrogen and phosphorous entering Iowa waterways and contributing to the dead zone in the Gulf of Mexico. Water Works officials say rising nitrate levels in the Raccoon and Des Moines rivers will soon require a new nitrate removal facility in Des Moines that could cost $80 million to $100 million.

Water Works on Tuesday stopped running its costly nitrate-removal facility after 97 consecutive days. This season marks the first time the utility has needed to run the facility during the winter to combat nitrates, according to Stowe.

The Iowa Farm Bureau and 11 farm groups released a joint statement Tuesday calling Water Works' decision a "startling disconnect from the scope and complexity of nonpoint water issues."

"Merely enacting regulations will do nothing to improve water quality," the statement read.

Utility officials said they plan to file the lawsuit Friday in the northern district U.S. Court. Water Works attorney Rick Malm will serve as lead counsel. The board approved spending $250,000 for legal fees. Gillette said it has already received several small checks from advocates to help with legal costs.

Des Moines Water Works claims drainage tiles in farm fields from northwest Iowa are contributing to high nitrate levels in central Iowa. The utility claims that water, nitrogen and other nutrients that enter intakes like this are eventually carried underground by drainage lines to streams and rivers that feed the Des Moines and Raccoon rivers, the source of water for 500,000 central Iowa customers.