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Seen from a riverboat that barely ripples the mirrored waters, the St. Croix River lives up to its reputation as a jewel of Minnesota waterways, a sparkling destination to get away from it all.

Even in its impaired condition -- fighting for breath from excessive phosphorous contamination -- the St. Croix on a bad day is healthier than the Mississippi River, which takes in the St. Croix near Hastings.

Comparison of the two major rivers was inevitable last week when about three dozen people working to improve St. Croix water quality cruised on the river south toward the Mississippi on the Afton Princess to celebrate their latest achievement.

The U.S. Environmental Protection Agency (EPA) approved a sweeping cleanup plan for the St. Croix that calls for public activism up and down the river to counter declining water quality.

The joint Minnesota Pollution Control Agency (MPCA)/Wisconsin Department of Natural Resources plan, known as a Total Maximum Daily Load study, is particularly important since the river flows through the St. Croix National Scenic Riverway, a national park.

"If we don't keep the river clean we might as well all go home because the national Wild and Scenic Rivers Act calls for clean, free-flowing rivers," Superintendent Chris Stein said.

Cleaner but not trouble-free

The St. Croix is "a far cleaner basin" than the Mississippi, said Chris Zadak, a basin project manager at the MPCA. Cleaner water from the St. Croix and its many tributaries dilutes sediments and contaminants in the Mississippi where they meet at Prescott, Wis.

Even now, the St. Croix has only one-sixth of the contamination that the Mississippi might have on its best day, Zadak said.

But even though the St. Croix remains pristine in comparison with many other rivers in Minnesota and Wisconsin, it struggles with many of the same problems.

Encroaching development, fertilizer pollution and storm water runoff from yards, streets and farm fields pushed the wider and deeper portion of the river, Lake St. Croix, onto Minnesota's impaired waters list in 2008.

Monitoring of water quality showed that excess phosphorus had created large oxygen-sucking algae blooms that will threaten recreational pursuits such as fishing unless those who depend on the river repair it, the study concluded.

The MPCA plan seeks to reduce phosphorous contamination in Lake St. Croix to 360 metric tons a year, the same as 1940s standards. Without corrective action, the study concluded, phosphorous contamination could grow to 540 metric tons a year by 2020.

"Now we have the real work ahead of us," Commissioner John Linc Stine of the MPCA told the assembled stewards.

Good news for the Mississippi

The next challenge for stewards of the river involves work on the 12 major tributaries and dozens of smaller streams that feed the St. Croix, said Chris Klucas, another MPCA basin project manager.

The St. Croix collects water from a giant basin that stretches into Anoka County on the west, nearly to Duluth on the north, and far into northwestern Wisconsin.

Much of the work to reverse the St. Croix's decline has begun in watershed districts up and down the river. More streams and lakes in the St. Croix watershed have landed on Minnesota's latest impaired waters list in recent years. Forty-two waterways were added earlier this year, bringing the total to 174.

But the St. Croix's interplay with the Mississippi means that one river's water quality can depend in part on environmental stewardship of the other, said Deb Ryun, executive director of the St. Croix River Association.

Findings released Thursday that show a much cleaner Mississippi in the Twin Cities than a generation ago were received with a cheer on the St. Croix boat excursion.

"The rivers are connected. Anything that comes up the Mississippi can come up the St. Croix," Ryun said.

That can include Asian carp and zebra mussels, and a backwash of contaminated water from the Mississippi in the spring when flooding causes a traffic jam-like effect where the rivers converge.

The St. Croix's deteriorating water quality has inspired a flurry of action up and down the river, with more to come in the wake of EPA approval. Government scientists do some of the monitoring. Trained volunteers do the rest.

"People love this river," Ryun said. "How can we not succeed?"

Details of the St. Croix study can be read at

Kevin Giles • 651-925-5037 Twitter: @stribgiles