Sediment strangling our rivers

Sediment from Minnesota's farm country threatens to choke off life in the state's two great rivers. A solution is no clearer than the water flowing through Lake Pepin.

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LAKE PEPIN, MINN. -- On a sweet spring day last week, Mike McKay looked out from a bluff above this breathtaking sweep of the Mississippi River and pointed out a scrubby little island that grows just a bit bigger every year.

"There's a saying in our house," he said. "The river giveth and the river taketh away."

For the past several decades, the river has mostly given to the lake he loves -- up to a million tons of mud each year, enough to bury the Foshay Tower from top to bottom.

At that rate, within this century the northern third of Lake Pepin will become a marsh, with a narrow channel dredged through its center for barge traffic. This grim accumulation represents a looming threat to one of Minnesota's scenic jewels. But it also signals a much bigger problem that in the past 70 years has fundamentally changed long stretches of state's two great rivers, the Mississippi and the Minnesota.

Now, for the first time, a clear picture is emerging of the source of most of that sediment -- the heart of Minnesota's farm country. It foreshadows exactly who will be asked to take on most of the responsibility for protecting one of the state's most treasured lakes and returning the rivers to health.

But more important, the state's long-awaited analysis of "sediment loading'' in the Mississippi -- and the public discussion it will trigger -- will set the stage for how, and if, Minnesota confronts the threats to all of its lakes, streams and rivers. It is by far the largest of hundreds of such assessments the state must conduct on all its polluted waters.

"If we get this right, we'll be able to solve everything else," said McKay, the general manager of Red Wing's St. James Hotel and head of the Lake Pepin Legacy Alliance, a citizen group. "It will bode well for Minnesota."

But getting it right means grappling with one of the state's biggest and most politically powerful industries: agriculture.

"The discussion needs to be had, and it needs to move forward," said Warren Formo, the director of the Minnesota Agricultural Water Resources Coalition, which represents farmer and agricultural groups.

The analysis, to be released later this month by the Minnesota Pollution Control Agency (PCA), concludes that sediment load in Lake Pepin has increased tenfold in the past century -- largely as a result of a sudden and massive transformation of a fragile landscape from prairie and wetlands to corn and soybeans.

The sediment comes mostly from the Minnesota River, and enters the Mississippi at the rivers' confluence near Fort Snelling. It blocks sunlight from reaching down through the water, suppressing the growth of plants and all the wildlife that depends on them.

When the Mississippi's current slows at the lip of Lake Pepin, the dirt settles out by the ton, raising the lake floor and collecting around the little islands like the one below McKay's bluff. To bring both rivers back to a point where everything from water lilies to wild swans can thrive again -- and to preserve Lake Pepin for the next generation -- the amount of sediment in the Minnesota will have to come down by 50 to 60 percent.

"That's the big one that will make or break this," said Norm Senjem, who headed the research project.

Changes in the land

The PCA's study on what is known as the South Metro Mississippi River was years in the making. It involved dozens of researchers, farmers, environmentalists, citizen groups and state pollution officials. It is, said Senjem, a consensus of the best science to date.

At its heart, though, is the story of how Minnesota was made -- and remade.

When the vast glacial Lake Agassiz drained southeast across the state nearly 12,000 years ago, it carved the deep, wide valley that now holds the Minnesota River and some of the richest farmland in North America. The Minnesota and its tributaries are still adapting to the shape of the young valley, cutting down through silt and clay, creating their distinctive high, sandy bluffs.

Much of the land in that third of the state was, and still is, flat. Instead of flowing away immediately after a rainfall, water collected in huge swaths of wetlands and in the deep soil of the prairie. In effect, the land was a massive sponge.

Then came the settlers and their plows. Sediment-dating studies reveal that mud deposits in Lake Pepin began rising in the mid-1800s, around the time that farming took hold. By the 1940s, farm fields accounted for 65 percent of the sediment in Lake Pepin, with the other 35 percent coming from erosion of stream banks and bluffs.

But after World War II, farming in Minnesota changed. Today, 62 percent of the Minnesota River Valley consists of row crops of soybeans and corn. And they don't tolerate wet soil very well.

The success of those crops is in large part due to a massive drainage project that in less than a generation has remade the southern Minnesota landscape. Below the soil, a capillary-like network of perforated plastic tubes drains natural wetlands and sheds water from millions of acres of cropland. They feed it into ravines, streams and ditches that never existed before. On its way down to the river valley, the water scours the fragile banks and bluffs, carrying loads of silt and clay into the Minnesota.

Since 1976, summer water flows in the Minnesota near Jordan have more than doubled, on average, according to the PCA. Today, farm fields supply only 35 percent of the sediment that finds its way to Lake Pepin. Most of the rest comes from eroding stream and river banks, primarily in the Le Sueur and Blue Earth River watersheds south of Mankato.

In short, humans have done in a generation what otherwise would have taken thousands of years to unfold.

"We have fundamentally altered the ecosystem of this entire watershed," said Shawn Schottler, an environmental engineer with the St. Croix Watershed Research Station.

Tradeoffs for farmers

Now, can people change it back?

Much will be up to the farmers who manage the land along the Minnesota's 335-mile length and its dozens of tributaries.

"We're talking about undoing landscape change on a landscape controlled by people who don't want to undo those changes in the first place," said Trevor Russell, program manager for the Friends of the Mississippi River. "Wow."

Many farmers, and the agricultural groups that represent their interests, say they are willing to do their part. Changes in farming practices have already improved conservation and helped return fish and eagles to the Minnesota River, they say.

But they want more research to determine how much of that massive geological process is natural, and whether increased rainfall has played a role. They also want a better understanding of what, if anything, they can do about it without paying an unfair or unnecessary price for changing how they manage the land and the water that flows from it.

"I get frustrated by friends who are scientific, but who are not charged with taking a look at the economics involved at all," said David Ward, who farms 2,600 acres of corn and soybeans near Mapleton, Minn.

Environmentalists say farmers have options. There are new drainage technologies and farming practices that can hold more water in the land. More and more farmers are adopting conservation tillage practices that slow the loss of both soil and water.

But that can come at a cost, especially now that commodity prices and land values are at a peak. And that explains why farmers have mixed feelings.

"This is a critical turning point," said Deborah Swackhamer, a leading water quality expert at the University of Minnesota. "I would like to see the state move toward a comprehensive policy approach, with consequences if farmers don't do what they need to do."

Others, including some environmentalists, say that is a non-starter. Farmers would go through the roof, said Patrick Moore, a member of CURE, a nonprofit in Montevideo that works on improving the Minnesota River. Better, he said, to rely on local communities and local agencies to reach common ground with farmers.

"Farmers are talking about these issues more than ever before," Moore said. "They are taking steps to do it."

The paradox is that federal environmental law requires Minnesota to develop a plan to address the sediment problem. But it does not require the state to fix it, nor does it include enforcement power over farmers.

In the end, said Senjem, the mud filling Lake Pepin will force a state that loves its farmers and its waters to confront what may be the most difficult challenge of all.

The real question, he said, is: "Are we up to this?"

Josephine Marcotty • 612-673-7394

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