– On the last glorious Sunday in August, lifeguard Maddi Danyluck walked down the most famous beach in Manitoba as the sun set fire to a bank of clouds right where the blue lake merged with the western sky.

Danyluk had one eye on the kids still romping in the water, but the other was on the turquoise stains that streaked the golden sand.

“There’s tons of it,” she said, wrinkling her nose at the blue-green algae lining the beach and floating like a dense mat of grass clippings in the shallows. “It just stinks.”

It also threatens to kill Lake Winnipeg, proudly known as the sixth Great Lake among the Canadians who flock to its famous beaches and fish its waters for walleye. In just two decades, pollution in the lake has doubled, with most of it coming from the Red River that runs north through the rich agricultural lands of Minnesota, the Dakotas and Manitoba.

The decay in Lake Winnipeg is a stark example of what Minnesota faces as its rivers are increasingly degraded by a transformation of the land around them: The price flows inevitably downstream, and it’s excruciatingly difficult to fix once pollution takes its toll on a river.

Visitors to Lake Winnipeg find that their treasured short summers are marked by increasing numbers of sometimes toxic algae blooms, which chase swimmers away from the beaches and foul the nets of fishing families that have made their living here for generations. Temporary dead zones — water devoid of aquatic life — are starting to appear in the lake’s vast northern basin, a sign that the lake may soon reach a tipping point.

While the Red River provides only 15 percent of the water in Lake Winnipeg, it carries almost 50 percent of the phosphorus that is creating the algae, mostly from the vast farmlands in Minnesota and North Dakota.

Now, after years of research and gentle pressure from Canadian governments, the United States and Minnesota have signed on to a simple plan called the Lake Friendly Accord: Cut phosphorus pollution from farms, cities and water treatment plants by 50 percent.

But so far it’s not going so well. Pollution in the Red River at the Canadian border has been rising since 1994, but there’s still little consensus in how to stop it. “We are going downhill,” said Jeff Lewis, executive director of the Fargo-based Red River Basin Commission, a cross-border organization charged with finding a solution.

The slow progress creates a sense of despair among the Winnipeggers who spend their summers in the cottage communities that ring the southern part of the lake. “It’s a very helpless feeling,” said Nancy Hodgson, who raised her children and now her grandchildren in the storybook village of Victoria Beach.

Property values have dropped, said her husband, Brian Hodgson, the reeve — or mayor — of the town, who fears the losses may reflect Lake Winnipeg’s growing reputation for pollution and algae blooms. Now kids are starting to cut their feet on the razor-sharp zebra mussel shells that litter the beaches — another gift from the Red River.

“I guess we have you Americans to thank for that, too,” he said, teasing gently.

Dramatic changes

The Red River of the North starts in Breckenridge, Minn., at the confluence of the Otter Tail and Bois de Sioux rivers. . From there, it forms the border between Minnesota and the Dakotas as it follows the path of a glacier that receded north 10,000 years ago. It zigzags for 500 miles through what was once a vast prairie region of grass and wetlands before opening up into Lake Winnipeg.

The prairies are long gone, plowed and ditched to create some of the richest farmland in the world. But in recent decades, agriculture has changed dramatically. Gone are most of the pastures, oats, sunflowers and wheat. In the western part of Minnesota, those crops have been replaced with chemically intensive corn, soybeans, sugar beets and potatoes, which now grow horizon to horizon all the way to the Canadian border.

Along with the crops came more drainage — tens of thousands of miles of perforated plastic tubing laid in the soil below corn and other row crops to move water off the land even faster. That coincided with major increases in precipitation starting in the early 1990s that have increased the ten-year average flow in the Red River by 50 to 60 percent.

For most Minnesotans, the Red River’s biggest problem is seasonal flooding that wipes out crops, inundates their towns and inspired the bitterly contested $3 billion Red River diversion project around Fargo, N.D.

Far less noticeable is that the Red River has become a massive storm sewer that sends increasing amounts of phosphorus, nitrates and sediment from Minnesota and the Dakotas north to Lake Winnipeg.

“It’s like a big gun barrel,” Robert Kristjanson, who along with his sons and daughters runs a commercial fishing business out of Gimli on the southwest side of Lake Winnipeg. “And we are on the other end.”

Kristjanson’s grandchildren are the sixth generation of Icelandic fisherman who first came to Gimli in the later 1800s. Today about 750 families still live much the same way. They spend weeks out on the lake in their boats and camped out on islands, filling their holds with whitefish, walleye — or pickerel, as they say — and goldeye for commercial markets around the world. In winter they stretch nets beneath the ice and haul fish to shore with Bombardiers, competing with the thousands of Minnsotans who come north for ice fishing there.

Lake Winnipeg, said his son Chris Kristjanson, is not like the cold, pristine Lake Superior — it’s teeming with fish and aquatic life. In fact, for now, he said, phosphorus may be making the lake even more productive by providing nutrients for life up and down the food chain.

But no one knows how long that will last, and Kristjanson is worried.

“This is not my living — this is my life,” he said.

Most of the algae grows in the much bigger, deeper north basin of Lake Winnipeg, where the clearer water allows the sun to penetrate and generate far more frequent and dramatic blooms than in the cloudier southern basin. Satellite images compiled by the Lake Winnipeg Research Consortium show great swaths of green that form when the water is warm and the wind is still.

“It can be half an inch thick for miles and miles,” said Greg McCullough, a scientist at the University of Manitoba who has studied pollution changes in the lake. And sometimes the blooms form toxins that can kill pets, cause skin rashes and contaminate drinking water.

Eventually, if the phosphorus continues to rise unabated, the intermittent dead zones that have been documented from time to time could become permanent. Those areas, where oxygen and aquatic life are depleted by a sometimes sudden shift in water chemistry, have launched contentious environmental fights around Green Bay in Wisconsin, Chesapeake Bay on the East Coast and at the mouth of the Mississippi in the Gulf of Mexico.

Nicole Armstrong, a manager in Manitoba’s water and environment division, said Lake Winnipeg’s reputation is far worse than it deserves: Water quality is still good. Manitoba is taking steps to reduce the phosphorus that comes from farms and cities in the province itself, about half the total load, she said. Canadians will spend about $1 billion in the next five years on the problem, including multimillion dollar upgrades to Winnipeg’s city wastewater treatment plants.

Even so, the dilemma gets a fatalistic shrug from Winnipeggers like James Gibson, who was watching his two little boys in red and yellow life jackets paddle in Lake Winnipeg on a sunny Sunday afternoon.

“There’s nothing we can do about it anyway,” he said. “It’s all coming from the Americans.”

Struggle in the valley

About 300 miles south, just east of Moorhead, Americans are trying to do something about it. But re-plumbing a landscape of 15,000 square miles is expensive and divisive.

The history of just one 3-square-mile piece illustrates the forces at work.

Down a gravel road way off I-94 east of Moorhead, the crops suddenly give way to cattails and water, and a half dozen white egrets sail like kites against the sky.

This is the North Ottawa Impoundment, an artificial wetland built by the state to hold the water that drains 75 square miles of farmland. It’s the poster child for a binational plan to reduce flooding and pollution along the valley by holding back 20 percent of the water that flows into the river — enough storage for a 100-year flood.

The statistics are impressive: The impoundment removes 84 percent of the sediment, 70 percent of the nitrogen, and 38 percent of the phosphorus by slowing down the water through a series of dikes and ponds and filtering it through plants. In a sharp contrast with the regimented landscape that surrounds it, the three-square miles are a destination for wildlife. Thousands of ducks dot the ponds and blue herons step carefully through the mud.

But it was expensive — $20 million. And it took 12 long years for state and local environmental officials to wear down local resistance and endless political fights to get it done. Local farmers and township boards even appealed to former Gov. Tim Pawlenty to cut the funds for the project from the state budget.

People in the community couldn’t stomach the idea of purposefully flooding farmland that their grandparents had drained through sheer grit and backbreaking work, said Larry Schneeberger, who farms 3,200 acres near the impoundment and who was among those initially fought the project. And local government officials hated the idea of giving up precious tax base.

Schneeberger finally changed his mind, largely because “I could see we weren’t going to win this one,” he said. And now he recognizes the benefits. Land around the impoundment no longer floods like it used to, and farmers can widen their ditches because the water now has somewhere to go.

But the scale of the plan is daunting — a reminder, say conservationists, that the cost of repairing a badly impaired river can be insurmountable.

The Red River Basin needs 200 similar water storage impoundments that would cost $2 billion to $3 billion — the same price as the massive Fargo diversion project. And they would require farmers to give up one to two percent of the agricultural land in the valley. So far, about a dozen are built or underway.

“It’s not inconceivable,” said Lewis, of the Red River Basin Commission. “But it is a great stretch.”

And some question whether it’s worthwhile.

“We are concerned about what goes down river — they are our neighbors,” said Eric Zurn, who farms with his father and brothers near Calloway, Minn. “But if land around here sells for $4,000 per acre, why would I want to lose one ounce of it? I want the next generation to be here.”

It’s a struggle that extends up and down the valley, said Lewis. He’s tried for months to find farmers or farm organizations to join a new basin-wide advisory group to come up with a long-range plan to reduce nitrates and phosphorus that flow into the river to help Lake Winnipeg. The group includes officials from wastewater treatment plants, Canadian governments, local governments, and state and federal agencies, but no one from agriculture, he said.

Warren Formo, who represents Minnesota agricultural groups on water issues, said that local farmers declined to participate because they believe that the outcome is predetermined.

“The overarching message that they heard is that the burden will all fall on them,” he said. In the meantime, he said, farmers throughout the valley are doing what they can to reduce the use of fertilizers.

But Lewis is frustrated. It’s a clear sign, he said, that “we are more willing to fight than to sit down and have meaningful discussions.”

Lately, Lewis has been trying to find other ways to involve farmers, including a novel experiment that originated in Manitoba — turning cattails into fertilizer for crops.

Minnesota’s first-ever cattail harvest got going during the last week of August as a forage chopper cut a swath through a stand of 6-foot-tall plants at the North Ottawa Impoundment. The stalks and fuzz arced up through the air and into Schneeberger’s trailer-truck that followed behind.

The idea is simple: The cattails suck up phosphorus from the water as they grow, then release it again after they die and decay. If the plants, with their phosphorus, are instead plowed into fields as fertilizer, both farmers and the water would benefit.

“If it works, there could be a huge demand,” said project coordinator Aaron Ostlund.

But on that long day in August, it didn’t work. The super fine cattail fuzz clogged the engine of Schneeburger’s truck, cracking the radiator. Then the ground-up cattails came out in useless, big clumps when they tried to run it through a manure spreader to scatter it across a field.

At the end of the day Schneeburger pulled out of the project — he couldn’t risk anymore equipment, he said.

“Sugarbeet is our king harvest,” he said. “That has to come first.”

After getting the bad news the next morning in his Fargo office, Lewis hung up the phone in resignation. They’ll have to try again next year.

“We knew it was going to be a struggle,” he said. “And it was.”