Farmers cause most of the run-off pollution in Minnesota's major rivers, and the state should force them to help clean it up, an unusual coalition of city and environmental groups argued Tuesday.

"It's a basic issue of fairness," said Dan Ness, president of the League of Minnesota Cities and also the mayor of Alexandria. He noted that city taxpayers and businesses in the Minnesota and Mississippi watersheds will be required to spend more than $1 billion for water cleanup in coming years.

The groups said the state Pollution Control Agency (MPCA) should force farmers to reduce pollution instead of relying on voluntary efforts to control field erosion that drains millions of tons of soil into rivers and lakes.

Their comments came on the final day for public comment on part of a massive effort by the MPCA to improve Minnesota waters.

After years of study, the agency has issued reports that pinpoint sources of sediment in the Minnesota, Mississippi and Blue Earth rivers -- three of 81 watershed districts in the state, with more reports coming through 2018.

These reports, however, set the stage for a much larger public debate over how to sharply reduce the pollution -- and how to pay for it.

"There's no question that the suggestions those groups are making should be considered -- will be considered -- but in the next stage," said Gaylen Reetz, director of the MPCA's water division.

Under current law, "whether we can force farmers to change their practices on drainage ditches and things like that, well, that's complicated," he said.

Farm groups say their members have adopted a broad range of conservation practices over the last decade that have greatly reduced soil erosion and chemical runoff.

Multiple local, state and federal agencies share responsibility for runoff pollution. And although those agencies "are cooperating better than I've ever seen before in my 30 years here, it's still somewhat messy," Reetz said.

It might help if farmers had area "one-stop shops" for help with pollution regulations and sources of help, he said.

Reports set goals, costs

The report on "sediment loading" for the south metropolitan portion of the Mississippi River says that to reduce pollution by 25 percent will require about $843 million from about 100 cities in the area -- cities responsible for about 6 percent, or 2,700 metric tons of sediment in the water, compared with 78 percent attributed to agriculture.

On the smaller but far more polluted Minnesota River, 10 cities will pay $175 million to help with a goal of reducing sediment by 90 percent, the MPCA estimates.

Environmentalists at the Tuesday news conference -- held in parking lot at the MPCA's St. Paul headquarters -- dumped out buckets of dirt to illustrate that farmers contribute 13 times as much sediment as cities.

"It is harder to pinpoint how much pollution is coming from a specific farmer's fields" than from a city or business, acknowledged Whitney Clark, executive director of Friends of the Mississippi River. "But we can't rely on voluntary efforts by farmers. We need incentives to help them do the right thing, but we also need to require them to do the right thing."

Farmers say they already help

Farmers long have argued that they help cities defray some of their pollution-control costs by buying farm equipment, seed and chemicals in those cities. They also argue that tight regulations would penalize the bulk of farmers who act responsibly.

"I understand that argument," Clark said. "But the fact is, millions of acres of land are coming out of the Conservation Reserve Program this year because of higher commodity prices. Farmers don't always do well, and the pressure to make money while you can is great.

"Enforcing the pollution laws can help level the playing field," he argued. "It will force the guys who are the bad polluters to clean up their act, and it will show that most farmers really are the good guys."

That is the notion behind a voluntary federal program launched in Minnesota in January, where cooperating farmers get the equivalent of a public seal of approval, plus access to cost-sharing federal money, for using good conservation practices.

State officials say it could be an important part of reducing sediment in Minnesota waters.

But Steve Morse, executive director of the Minnesota Environmental Partnership, was less hopeful: "It's a nice idea. But after 70 years of voluntary programs, here we are today with agriculture the major polluter of our rivers. We need a tougher approach."

Warren Wolfe • 612-673-7253