Dayton argued that the threat to Minnesota's fabled 10,000 lakes, rivers, streams and wetlands is "a wider, deeper crisis" than the threat that mining poses to the Boundary Waters Canoe Area Wilderness. It won't be solved, he said, unless the public develops a clean water ethic.

"Clean water is your right, it's also your responsibility — and mine too," Dayton said.

Dayton was short on strategies for achieving the new goal, which he described as a grass-roots "call to action" — as opposed to a regulation. He said local communities must assess their own particular water problems and consider solutions, adding that he plans to hold a series of public meetings around the state this year where staff will gather recommendations that he will present to the 2018 Legislature.

Dayton drew laughs when he noted the press corps in attendance, saying that half were there to hear him and "the other half are here to see if I pass out." He was referring to a fainting episode Jan. 23 during his State of the State address at the Capitol.

Clean water has become a priority for Dayton, who leaves office in 2018, and he's been exhorting citizens to ratchet up efforts to conserve and protect their lakes, rivers and streams since last August, when he launched his "Year of Water Action" campaign. One of his other marquee initiatives — a new buffer law requiring strips of vegetation to be planted along public waterways to filter runoff — has raised hackles among some farmers who feel it violates their property rights.

Meeting with reporters after his address, Dayton answered several questions about his health. He said his prostate cancer is "treatable and curable," with no evidence it has spread; treatment will start shortly.

He also said the public generally does not recognize the danger to Minnesota's water, describing clean water as one of his core missions during in his final two years in office.

The 25 percent reduction by 2025 covers all pollutants, but the key culprits are nitrogen, phosphorus, chloride from road salt, E. coli bacteria and sediment. It's a "stretch goal" considering Minnesota's current efforts are expected to yield a 6 percent to 8 percent reduction in pollutants by 2032, said Minnesota Pollution Control Agency Commissioner John Linc Stine.

Environmentalists cheered Dayton's target but said the devil is in how to reach it. Such a deep reduction in pollutants will require some drastic changes, said Whitney Clark, executive director of Friends of the Mississippi.

State research shows that about 78 percent of the nitrogen and 40 percent of the phosphorus in Minnesota's major rivers comes from crop fertilizers, but the governor did not single out farmers in his remarks.

Harold Wolle, president of the Minnesota Corn Growers Association, said his members welcome the 25 percent goal. The governor's "bottom-up approach" — listening to the public and collecting their ideas — will work better than what he sees as Dayton's top-down approach with the state's new buffer law.

New equipment and technology will help farmers achieve the reduction, Wolle said. "It's going to be precision application of our farm nutrients that will allow us to make the next big achievement in reducing pollutants in our water supply," Wolle said.

Clark expressed skepticism, arguing that better fertilizer management alone won't get the state to a 25 percent reduction. Clark said he thinks the long-term solution is finding new markets for perennial crops, which can reduce soil runoff and chemical use, and helping farmers shift away from corn and soybeans.

State officials have already agreed to a long-term goal of reducing nitrogen and phosphorus levels in the Mississippi by 45 percent. That cleanup is part of a nutrient reduction plan among the 12 states along the Mississippi to address the dead zone in the Gulf of Mexico. The broad new goal will help that more targeted effort, Dayton said.

Jennifer Bjorhus • 612-673-4683