The Red River is polluted by excess sediment and damaging nutrients for most of its length, while large sections are becoming unsafe for swimming because of bacteria from manure and broken septic systems, according to a major new assessment by the Minnesota Pollution Control Agency (MPCA).

One of the main culprits is the river’s volume, which has increased dramatically from decades of irrigation and agricultural drainage that have caused the region to become “one of the most artificially drained areas in the world,” the study found.

The agency found that just about every creek and stream feeding the Red River has been altered by highly effective drainage systems that push far too much water too quickly downstream in the spring and after downpours, causing parts of the river to flood. Once flooded, the river picks up extra runoff, sewage and manure and carries it downstream. During summers, when there is less rain, the creeks and streams run dry, placing stress on fish and insect populations.

There’s no single solution, said Jim Ziegler, MPCA regional manager. “But we know there’s a need for more [water] storage so during the spring runoff or heavy rains, the water can be … slowly released over time to maintain that base flow.”

The Red River study is part of a multiyear effort by the MPCA to assess all of Minnesota’s major rivers; it has already completed reports on the Mississippi and Minnesota rivers. The St. Croix is next.

The findings are not particularly surprising, said Ted Preister, executive director of the Red River Basin Commission, a nonprofit group made up of stakeholders and representatives from the various government agencies involved.

“It confirmed what we already know,” Preister said.

But, he said, it’s the most accessible and concise study to lay out the challenges and potential solutions.

The Red River, which provides drinking water to tens of thousands of residents along the border between Minnesota and North Dakota, runs north into Canada before emptying into Lake Winnipeg. The two countries, two states and dozens of watershed districts and municipalities along the river have been studying the basin’s increasing pollution for years, especially as it unloads into Lake Winnipeg.

The lake, the 10th-largest in the world, has been haunted by seasonal algae blooms fueled by excess nutrients. The Red River is responsible for more than half the phosphorus polluting the lake, despite contributing only about a tenth of its water supply, according to a 2017 U.S. Army Corps of Engineers study.

The United States and Canada have signed a treaty to cut the Red River’s phosphorus loads by half on both sides of the border, but neither country has a plan to accomplish that.

Fewer fish

In Grand Forks, N.D., the average daily flow of the river is about twice what it was in the 1960s, according to the study. That high and fast flow is eroding riverbanks, and is due largely to drained wetlands and the installation of “extensive tiling and ditch systems.”

The study found that nitrogen levels are creeping up throughout the river’s length, which can pose a threat to drinking water. While not yet a health threat, nitrogen becomes much more costly to filter out of water than to keep out of the river in the first place.

Fish populations are doing relatively well, according to the study. But fish are dying off in the river’s downstream reaches, dropping from 22 species near the river’s headwaters to just 13 at the Canadian border. That drop-off reflects loss of habitat caused by “a more cultivated and drained landscape” in the northern part of the river.

The study recommends that farmers in the region reduce tillage to keep soil on their fields and plant more cover crops to build up a carbon base, which would allow the soil to hold more water. Municipalities and homeowners need to improve septic systems and stormwater and wastewater treatment facilities to cut the amount of phosphorus released into the water, the authors found.

Communities that can’t build or upgrade full wastewater plants should work with the state to cut pollution in other ways, potentially by land or riverbank restoration projects, Ziegler said.

The report does not recommend any new regulations or enforcement strategies; rather it urges the state to work with local municipalities and watershed districts to develop local goals and plans to meet those goals.

“We need to work cooperatively, and now we have more concrete information, so when we’re working with local partners we can use it in the planning processes,” Ziegler said.