DULUTH — Walleye and sturgeon anglers have known it for years, but the Rainy River has now received a water quality grade of "excellent," signaling a return from the depths of choking paper mill and sewage pollution 50 years ago.

The Minnesota Pollution Control Agency on Monday, Aug. 10, released a long-range report on the health of the big river that runs for 86 miles and forms the U.S.-Canada border between Rainy Lake on the east and Lake of the Woods to the west.

The MPCA in 2016-2017 conducted extensive tests at sites up and down the river checking for pollution, sediment, oxygen levels, fish and insect populations. The river “consistently met standards in all the locations we monitored,’’ Jesse Anderson, research scientist for the MPCA, said Monday.

Researchers found 42 species of fish and minnows in the river (10 of those considered sensitive to pollution), including sturgeon, longnose dace and smallmouth bass. That led to an “excellent” rating for fish communities “among the best of the best in Minnesota,’’ Anderson said. That includes walleyes over 10 pounds and sturgeon over 50 pounds regularly caught, and mostly released, by anglers.

Students in the Nashwauk-Keewatin fishing class last year caught this 59-inch sturgeon on the Rainy River. State regulators say the river, which has been recovering for decades, is now officially excellent water quality. Contributed photo.
Students in the Nashwauk-Keewatin fishing class last year caught this 59-inch sturgeon on the Rainy River. State regulators say the river, which has been recovering for decades, is now officially excellent water quality. Contributed photo.

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Scientists also monitored macroinvertebrates, creatures like mayflies and dragonflies that make up the base of the river’s food chain, to gauge the river’s health. The numbers and diversity of aquatic insects indicate a healthy community. The river even supports some highly sensitive species, like finger-net caddisflies and common stoneflies, that have almost no tolerance for pollution.

The report is a “celebration of the great work that’s been done over the years,’’ Nicole Blasing, watershed manager for the MPCA, said.

It’s the fourth in a series of reports on the health of the state’s biggest rivers, following less-glowing grades for the Mississippi, Minnesota and Red rivers.

The report credits two major factors for the excellent health of the Rainy River — namely the enforcement of clean water regulations on mills and municipal sewage plants on both sides of the border — and the fact millions of acres of the river’s 21,000-square-mile watershed remain undeveloped and protected in Voyageurs National Park, the Boundary Waters Canoe Area Wilderness and Quetico Provincial Park.

As recently as the 1970s, the Rainy River was unfit for any swimming and was inhospitable to fish, especially lake sturgeon, which were essentially extinct from the main river but hung on in a few cleaner tributaries. For decades, paper mills in International Falls and Fort Frances simply dumped their mill waste directly into the river.

And communities along the border dumped poorly treated or untreated municipal sewage into the river as well. Chunks of fibrous debris fouled fishing lines and waste material covered spawning beds and used up the oxygen fish and small aquatic creatures needed to thrive.

A delta of paper mill waste can be seen running out of the International Falls paper mill and into the Rainy River in this undated 1950s photo. State regulators say the river has now fully recovered from its heavily polluted years. Minnesota Pollution Control Agency photo.
A delta of paper mill waste can be seen running out of the International Falls paper mill and into the Rainy River in this undated 1950s photo. State regulators say the river has now fully recovered from its heavily polluted years. Minnesota Pollution Control Agency photo.

The International Joint Commission, which oversees all border waters between the U.S. and Canada, urged immediate action in the 1960s, calling the river a “threat to human health.” Eventually, based on Canada’s Environmental Protection Act of 1971 and the U.S. Clean Water Act in 1972, regulatory agencies did just that, imposing new rules on cities and mills that have gradually ramped up over the years.

By the 1980s, pollutants going to the river had dropped dramatically and recovery was well underway, spurring a trophy fishery and rapidly increasing recreation on the river, now a destination for anglers from across the Midwest.

Author Jamie Benidickson described the Rainy River comeback, saying: “Historically, perhaps the most significant demonstration of successful environmental remediation in the region is the long-term recovery of the Rainy River from a state of devastation in the 1950s.”

Unresolved phosphorus problem downstream

The Rainy River, which runs for 86 miles between Rainy Lake and Lake of the Woods, just got an excellent rating for fish populations and water quality after extensive field testing.  Minnesota Pollution Control Agency photo.
The Rainy River, which runs for 86 miles between Rainy Lake and Lake of the Woods, just got an excellent rating for fish populations and water quality after extensive field testing. Minnesota Pollution Control Agency photo.

MPCA officials note that there are still unresolved issues involving the river, namely heavy phosphorus levels in Lake of the Woods that are spurring annual summer algae blooms.

It’s believed at least part of that problem is coming from the Little Fork River, which flows into the Rainy River and which carries a high level of sediment after rain events and spring snowmelt. That sediment also carries phosphorus, which then flows into Lake of the Woods feeding the algae.

Mike Kennedy, Rainy River watershed project manager for the MPCA, said the agency this summer is starting a two-year “sediment fingerprinting” project to study how much phosphorus-carrying sediment is flowing down the Little Fork and how much of that is contributing to the problem in Lake of the Woods. The next step would be projects to reduce sediment runoff in the Little Fork watershed.