St. Croix River

Two recently released reports summarize water quality, the health of fish and bugs, and strategies for continued protection of the St. Croix River.

The St. Croix River, treasured for its natural features, cultural significance, and exceptional fishing and boating, is heralded by officials in Wisconsin and Minnesota as a shining example of successful water protection with one warning: don’t stop now. The St. Croix is among the nation’s first rivers designated for protection under the federal Wild and Scenic Rivers Act, and today 90% of its wetlands in the northern areas of the Minnesota portion remain untouched. Two new reports by the St. Croix River Association and the Minnesota Pollution Control Agency summarize water quality, the health of fish and bugs, and strategies for continued protection.

The reports were released as the nation marked the October anniversary of the landmark Wild and Scenic River legislation. They illustrate a need to protect against increasing development that could endanger the St. Croix River, which forms the Minnesota-Wisconsin border and is enjoyed by hundreds of thousands of people each year.

Both reports call on local, state, and national partners to continue working to preserve natural features to guard against climate change. They also call for reductions in the levels of phosphorus that promote algae growth, which can harm fish and hinder recreation. They also note that while still relatively low, levels of chloride — which can harm freshwater fish and other species — are increasing in the river.

“We are blessed with a truly special wild and scenic river, a generally healthy and intact riverine system seldom seen elsewhere. But the river is vulnerable,” says Deb Ryun, SCRA Executive Director. “From preventing the spread of invasive species to being mindful of everyday actions on water quality, everyone can do something to help preserve the St. Croix.”

The SCRA’s State of the St. Croix River report describes the river’s special features:

• A significant stand of wild rice remains below Upper St. Croix Lake, with smaller patches found along other sections of the river. Wild rice is a culturally important food for Indigenous communities in both states.

• Unlike most rivers of this size, the St. Croix continues to support a thriving mussel population: 41 different types of mussels live in the river, and five are federally listed.

• Native mussels are threatened by the zebra mussel, an invasive species that attaches to other mussels, preventing them from breathing, eating, and reproducing.

• Numerous invasive species threaten the river’s native plants and wildlife, including yellow iris, purple loosestrife, and Asian carp.

The MPCA’s report, “The St. Croix River: Study of the River’s Health,” assesses the river’s water quality compared to Minnesota’s water quality standards, from the point where the river enters Minnesota to its confluence with the Mississippi River. The agency found that the river meets standards for aquatic life and recreation — such as fish and swimming — except the stretch from the Taylor Falls dam through Lake St. Croix, which suffers from excess phosphorus and algae growth at times. This part of the river is on Minnesota’s impaired waters list.

The MPCA report notes:

• Phosphorus concentrations are decreasing, according to long-term monitoring by the Metropolitan Council, evidence that strategies such as fertilizer management and wastewater treatment are working.

• Fish and bugs are in excellent to good condition: MPCA scientists found 63 fish species while sampling, including four considered rare or that need unique habitat to thrive. The diversity is a strong signal that the health of the St. Croix River is in good condition.

• Though the fisheries are in excellent condition, limits remain on how much fish can be consumed safely because of mercury and PCB levels, a common problem throughout the state.

• There is an emerging threat from PFAS, a group of synthetic chemicals used in many consumer products. Some of the chemicals are known to be hazardous to human health.

“This is great example of federal, state, and local protection policies that work and result in excellent conditions overall. Our job now is to continue working together at all levels in protecting this river, especially with emerging threats to water quality,” said Pam Anderson, Manager of Surface Water Monitoring for the MPCA.

The reports note that continuing protection strategies are crucial to safeguarding the river’s good water quality and biology, and protecting against climate change. For example, maintaining the basin’s wetlands and forested areas will prevent harmful runoff to the river; increasing agricultural practices will reduce runoff of sediment and fertilizer to the river and its tributaries; upgrading wastewater treatment will reduce phosphorus discharges to the basin; and expanding urban stormwater management will help prevent runoff of pollutants and warming of river water temperatures that could harm mussels and other river life.

The MPCA report is the final in its series on Minnesota’s big rivers. Previous reports focused on the Upper Mississippi, Minnesota, Red, and Rainy rivers.

For more information on the State of the St. Croix River report, visit the SCRA web site. See the MPCA web site for the Study of the River’s Health.