See also: What’s in our drinking water? and Is Minnesota at a turning point?

On a recent summer day, Dylan, Madysen and Colten King escaped the heat in time-honored Minnesota fashion: with a swim in a lake.

But the King children’s trip to Lake Byllesby in southern Dakota County had another element now found in lakes across the state: huge, unsightly algae blooms.

“It looks gross, but it gets better as you go out farther,” 9-year-old Colten said as he and his siblings splashed a few yards from the beach, just beyond a film of blue-green algae hugging the shoreline.

Lake Byllesby, a body of water created by a dam on the Cannon River, is a good example of a state lake dogged by uncertain water quality. Byllesby is a popular summer spot for fishing, boating and swimming, but state water-quality data show that it doesn’t fully support any of those activities.

More than 600 lakes impaired

In southern parts of the state, the Minnesota Pollution Control Agency considers 75 percent or more of lakes and streams to be impaired. Overall, more than 600 of Minnesota’s famous 10,000 lakes are rated as not able to fully support aquatic recreation — including even the remote Lake of the Woods, which has regular summer algae blooms. About one-fifth of the 2,500 stream segments rated by the MPCA fall into the same category. Meanwhile, thousands of other lakes and streams haven’t been fully rated.

Lakes like Byllesby are the targets of a war that Minnesota has been waging for two decades, with decidedly mixed results. But unlike past battles against such poisonous pollutants as mercury, the primary target here is phosphorus, a naturally occurring chemical that’s also found in fertilizer and human waste. It comes from cities, suburbs and farms alike, but once phosphorus seeps into the water, summer algae blooms often follow.

A persistent effort to reduce this pollution has had some victories; right now, about twice as many Minnesota lakes are getting clearer as are growing worse, a sign of declining algae. But waters in large parts of the state remain so polluted that some environmentalists fear they could be a lost cause, and the pollutants that cause algae blooms are on the rise in many parts of the state.

Lakes vital to Minnesota economy

Gross-looking lakes could have real costs. Minnesota’s $13 billion tourism industry is built on a foundation of scenic lakes and streams for fishing, boating and swimming.

“Our natural resources always comes near the top as to why people come here,” said John Edman, director of Explore Minnesota, the state’s tourism office.

“When our natural resources are in some way impaired, it rises on our radar, because that affects our industry. We have to do everything we can to keep our tourism industry strong.”

When a lake is in the middle of an algae bloom, it can keep “people from using those lakes … and getting full enjoyment out of those lakes,” said Lee Ganske, a water-quality monitoring expert with MPCA.

“At the same time, those same things that are impacting the recreational value of the lake may also be degrading the ecosystem of that lake, degrading the fishery of that lake.”

Governor demands action

In his April State of the State address, Gov. Mark Dayton painted a grim picture of Minnesota’s waters.

“Some lakes, rivers and streams all over our state have become dangerously polluted — so bad that fish can’t live in them and people shouldn’t swim in them,” Dayton said. “One Minnesotan living in a town providing free bottled water to its residents after its water treatment plant malfunctioned, said, ‘That’s just the way it is, living here.’

“I disagree,” Dayton continued. “That should not be ‘just the way it is,’ living anywhere in Minnesota. No one person or industry is responsible for our state’s deteriorating water quality, but every one of us is responsible for improving it.”

Algae can kill dogs, sicken humans

Algae in Minnesota’s lakes does more than look gross — though that can be bad enough for a state marketing its pristine outdoors to tourists. Some types of algae can be toxic — and even fatal to smaller animals, such as dogs.

“We every year see a couple of dog deaths,” said Trisha Robinson, supervisor of the waterborne diseases unit of the Minnesota Department of Health. “Symptoms can really vary, but people may experience vomiting or diarrhea. They may have a rash. It can cause more respiratory symptoms with cough, sore throat (and) headache.”

There have been no human deaths associated with algae blooms in Minnesota, and most years the state doesn’t see any algae-caused illnesses, either — though Robinson said such illnesses may go unreported.

Most lakes impaired in south, fewer in north

The story of how Minnesota’s lakes are resisting pollution varies by region, watershed and lake, with some areas doing quite well and others doing poorly.

St. Olaf Lake in Waseca County, for example, has lost several feet of visibility on average over two decades of measurements because of algae increases. Lake Hallett in St. Peter was clear to a depth of 12 to 15 feet in the late 1990s, but recent measurements show clarity has shrunk to as little as 7 feet.

Other lakes, predominantly in southern and western Minnesota, are so badly contaminated that “you can say that whether they’re getting slightly better or slightly worse is not even an important issue,” Ganske said. “The lakes are in terrible condition, and you can only point to very slight improvements over a period of decades.”

Some lakes are improving

But other lakes have shown considerable improvements. Lake of the Woods, which straddles the border with Canada, still has algae blooms but has seen major declines in its pollutant levels in recent decades — a change related to improvements in the Rainy River, which flows into it from the south.

“The Rainy River was just in terrible shape back 30, 40 years ago,” said John Bruggeman, chairman of the North Koochiching Area Sanitation District, which covers the area at the head of the Rainy River along Minnesota’s border with Canada. “All the effluent from the paper building … pretty much everything went straight to the river back then.”

But the 1972 federal Clean Water Act and other laws passed in Minnesota and Canada forced cities, farms, paper mills and other sources of pollution in the lake’s watershed to clean up.

Phosphorus loads on the Rainy River, for example, have fallen from about 1,500 tons per year in the 1960s to about 500 tons per year today — though that’s still above the river’s natural level, said Todd Sellers, executive director of the nonprofit Lake of the Woods Sustainability Foundation.

Lake Byllesby much clearer than past

Similarly, Lake Byllesby’s periodic summer algae blooms are actually an improvement.

“When I was growing up on the lake, you couldn’t skip a rock; it was so rife with algae,” said Earl Benson, whose family has owned property along the lake for more than half a century. “Now there are times I can see the bottom of my lake from the end of my dock. That hasn’t happened in 50 years.”

Of course, “impaired” lakes can be safe to swim in much of the time — a good thing, because Minnesotans are swimming in them.

“Even the most impaired water bodies in the southern part of the state still are used,” said Ganske, the MPCA water expert. “People might be swimming in the first part of June, and after that, they stay out because the water turns so green.”

“Impaired” lakes can still be used

Watching her children frolic in Lake Byllesby, Carrie King said she wasn’t too worried by the algae or runoff.

“I swam in the horse tank, and I turned out just fine,” King said.

Neither was Justin Watkins, an MPCA scientist who studies Byllesby.

“I went swimming in it last year with my kids,” Watkins said. “There were algae present. You could see algae in the water.”

Swimming in an algae-filled lake doesn’t mean someone will necessarily get sick — only that the risk is higher than scientists are comfortable with.

Only some kinds of algae are toxic

Robinson, supervisor of the health department’s waterborne diseases unit, said only some kinds of algae are toxic — so-called “blue-green algae,” which looks like “pea soup” or spilled paint and can smell swampy.

But “there’s no way you can tell just by looking at it that it does have these toxins,” Robinson said. “That’s why our main message is, ‘If in doubt, stay out.’”

“Even in those cases where a water body … may show up on the map as impaired for swimming use, the risk of contracting an illness would still be very low — but still above that threshold,” Ganske said. “The threshold needs to be set somewhere.”

State funds water quality improvements

The low-hanging fruit for improving water quality are “point sources” — factories, sewage systems and other human products where a single facility or system introduces large amounts of pollution into the environment. Improving one facility can greatly reduce the pollution flowing into a river.

On this front, Minnesota has made considerable progress. A range of state and federal money, including funds from the 2008 Legacy Amendment, allows Minnesota to offer grants and low-interest loans to towns and cities that need to improve their water system.

In a typical year, the MPCA distributes $100 million to $300 million in this aid, mostly as loans. This is targeted at a range of pollutants, not just phosphorus, but some of the money goes to cut down on the algae-boosting chemical.

Phosphorus declining in some areas

Across Minnesota, water quality is improving in about 20 percent of its lakes, state officials say. But about 10 percent of the lakes are getting dirtier, and the rest are stable. Some pollutants in rivers and streams are decreasing while others, notably nitrates from farm runoff, are increasing, according to state officials.

For years, Lake of the Woods saw much of its phosphorus load coming from paper mills and cities, such as International Falls, at the head of the Rainy River. Over the decades, however, both sources have improved their discharge practices. International Falls recently spent $14 million to update its water-treatment plant, including a $2 million phosphorus filter — paid for with the help of an MPCA grant.

Lake Byllesby’s improvements have come from water-treatment upgrades at three upstream cities: Faribault, Northfield and Owatonna. And lake phosphorus levels have fallen by as much as 75 percent over the past decade.

“That’s had a very noticeable effect,” Watkins said. “It’s still impaired. It’s less severely impaired, very noticeably.”

Improvements not enough

Dakota County parks director Steve Sullivan said improvements to Lake Byllesby have been dramatic but aren’t enough.

“We’ve got a long way,” said Sullivan, whose department manages Lake Byllesby Regional Park, but “there’s a long way to go before we can say that the Cannon River is being managed at a best management practice level.”

Farm, lawn runoff harder to address

But much of the phosphorus, as well as nitrates, in Minnesota waters doesn’t come from easily identifiable point sources. Instead, they come from farms, private septic systems and other spread-out sources that combine to have a big impact. Lakeside development can also increase pollution by replacing natural buffer strips with manicured lawns.

The federal Clean Water Act exempts agriculture from requirements that regulate other “point-source” polluters, a longtime sticking point for environmentalists that makes it harder to identify the precise origins of much of the pollution in southern Minnesota.

But it’s not impossible, and after several years of intensive monitoring, the MPCA now is able to show how, in some cases, individual farms are contributing.

Dayton pushes for buffers

Targeting these sources of pollution can anger a lot more people.

Dayton faced major pushback this year when he proposed requiring more natural buffer zones around waterways to stop pollution before it reaches the water. The governor, legislators and farm groups ultimately struck a compromise that scaled back his approach to appease farmers.

“Each farm is different. Each farmer’s practices are different,” said Bruce Peterson, a Northfield farmer who is president of the Minnesota Corn Growers Association. “It’s important there is a little bit of flexibility built in. Rather than have it be top down from the DNR, it is important to keep (enforcement and oversight) at the local level.”

Buffers a solution, but are they enough?

In the coming year, the state Department of Natural Resources will designate 110,000 acres statewide for protection. Much of that will be shoreland along state-protected waters, but public ditches also eventually will gain buffers.

Benson, the Byllesby lakeside property owner, said he believes that with recent improvements in farming practices and waste water treatment, Dayton’s buffer strip initiative could be the final piece of the water-quality improvement puzzle.

“The buffer strips, in my estimation, will be the final step in making these lakes more sustainable,” Benson said.

Peterson, on the other hand, said buffers are getting too much attention.

“We’ve always been a supporter of buffers, but they are not the only thing that affects water quality,” Peterson said.

Fixing problem can take time

While some lakes can see improvements in a matter of years, others can take centuries to recover from pollution.

Byllesby can see relatively quick turnover of its water — especially in wet years when the Cannon River current picks up.

The water of Lake of the Woods, in contrast, sticks around much longer before it is cycled out. So even though less phosphorus now is flowing into the lake, its algae blooms haven’t grown any better.

“There’s an accumulation of phosphorus built up from the sins of our past,” said Sellers of the Lake of the Woods Sustainability Foundation.