Many of the lakes and streams in southwest Minnesota are unsafe for both people and fish to swim in, according to a report by a state agency that monitors pollution levels.

High nitrate, bacteria and sediment levels are the main reasons that few of the water sources in the area can support aquatic life or recreational activities like swimming and fishing, according to the Minnesota Pollution Control Agency (MPCA).

A report issued in the last quarter of 2014 documents what many researchers in the state have known for some time, but experts say many obstacles exist to cleaning up the water.

Nitrate — a chemical often used by farmers growing crops like corn — is of particular concern to researchers as they've watched nitrate levels increase over time, said Glenn Skuta, water monitoring section manager for the MPCA.

The report recommends "efforts to control sediment," including keeping cattle away from bodies of water and controlling the amount of chemicals that run into streams from farms.

"Only by collaborating with landowners will the agricultural economy of the region move forward in a sustainable way that does not neglect water quality," the report says.

Of the 93 streams the study examined, only three were considered able to fully support aquatic life and only one could fully support aquatic recreation, the report said.

Experts on water quality in the state have viewed the region as a trouble spot for a while, said Deb Swackhamer, environmental health sciences professor at the University of Minnesota. She said the MPCA's study is the first intensive look at the Missouri River basin, which covers nearly 1,800 square miles.

"We've known that the agricultural areas have more pollution problems than other parts of the state," Swackhamer said. "This is the first form of documentation of that."

But it's difficult to tell how much runoff individual farms are producing and which lakes and streams the runoff goes to, she said. And it may be just as difficult for farmers to tell how much runoff they are producing. The lack of regulations on runoff makes limitations difficult to impose.

"They don't want to be polluting the water, either," she said, "but there's no mechanism to make them extra good citizens here."

This is where Gov. Mark Dayton's proposal to buffer all waterways in the state with 50 feet of grass comes in, Skuta said.

"If we had better buffered streams, they would be much more protected," Skuta said.

Any approach to cleaning the water would take time, though, he said, adding that "we have greatly disturbed the land there."

The MPCA's next steps include formally identifying the sources of the pollution and then issuing a final report spelling out specific avenues for correcting the problem, Skuta said.

The Associated Press contributed to this report

Anne Millerbernd is a University of Minnesota student on assignment for the Star Tribune.