By Tim Krohn
Free Press Staff Writer
Seth Greenwood has watched parts of Seven Mile Creek County Park between Mankato and St.
“ The Minnesota River is eating the bank away,” said the Nicollet County public works director. “It’s really bad on that bend on the river. Five to 15 feet of bank has gone just this year.”
Much of that sediment will likely end up in the Mississippi River and settle to the bottom of Lake Pepin.
While intense efforts to improve the Minnesota River have gone on for 20 years, now there is a major convergence of better data and mounting political pressure that is bringing to a head problems of suspended solids in the river.
The issue is creating growing friction between farmers and environmentalists and residents on Lake Pepin who are suffering from the Minnesota’s pollution.
The millions of tons of sediment getting into the river is emerging as the keystone issue facing the river basin. The impacts on the Mississippi, Lake Pepin and the river basin’s contribution to the Gulf “dead zone” are sweeping and the potential solutions expensive, controversial and complicated, considering the Minnesota watershed covers 16,000 square miles.
Decades of scientific research — bolstered by new techniques such as using radioactive isotopes to trace where dirt particles originated — offer a few major findings:
■ The amount of sediment getting into the river has increased dramatically — tenfold its natural rate by some estimates.
■ Two-thirds or more of the river’s sediment load comes from eroding streambanks and bluffs.
■ Compared to the past, there is much more water flowing into the river more quickly. Part of that comes from more frequent and heavy rains. But more and more, researchers are convinced the high, fast waters tearing into streambanks are largely the result of extensive farm drainage that has changed the hydrology of the landscape.
■ The more powerful flows are altering the river.
The Minnesota River from Mankato to St. Paul has widened by 50 percent since 1938. The scene along Seven Mile Creek County Park is playing out all along the lower half of the Minnesota River.
Farm groups have begun a more aggressive campaign to counter the image of drainage as the primary foe, pointing to research that high bluff erosion and bank erosion are coming from more precipitation.
But researchers increasingly say otherwise.
“ We don’t know absolutely everything,” said Norman Senjem, who recently retired from the Minnesota Pollution Control Agency after many years of overseeing river research. “But post-World War II to about 1980 is when we see the biggest uptick in sediment, the biggest uptick in Lake Pepin filling in. It’s the time of increased mechanization in agriculture.
“Precipitation plays a role, but primarily it’s landscape changes.”
Shannon Fisher, who heads the Water Resources Center based at Minnesota State University and is director of the multi- county Minnesota River Board, said he’s seen enough credible research to believe farm drainage is a major factor.
“In my opinion, the drainage we’re doing is having an impact on the hydrology and we’re going to have to address it. Water storage (on the landscape) is going to be very important, and it’s hard to sell to people as we put more tile in the ground.”
The latest study to peg farm drainage as the culprit was recently released by scientists at the St. Croix Watershed Research Station and the University of Minnesota. The research included examination of 70 years’ worth of records on rainfall, flow and land use changes along the 21 tributaries to the Minnesota River.
Shawn Schottler, one of the scientists who worked on the research, said everyone agrees streambank and bluff erosion are putting a majority of sediment in the river. Their latest study looked at how much of that could be tied to increased precipitation.
“Of course the (river) flow goes up when it rains more. Precipitation has gone up about 8 percent since 1940. Has flow gone up proportionally with that? No, it’s gone up more than that.” And Schottler said climatology records show precipitation has not increased in May and June in southern Minnesota, months that river levels are often highest.
Schottler said erosion of riverbanks and widening of the channel are natural occurrences on any river, but it’s been greatly accelerated on the Minnesota. And while much of the sediment that erodes into rivers under normal conditions settles somewhere in the same river, sediment in the Minnesota is flowing out into the Mississippi at a higher rate.
“If you go to non-ag watersheds, there is still erosion but no increase in sediment leaving the river.”
Fisher worries that limited funding to help improve the river may be targeted to a tiny portion of the problem.
There are two things involved in looking at suspended solids in the river: the physical sediment (dirt) and the biological. The biological side includes things such as algae blooms created by excess phosphorus in the river.
Much of the focus has been on reducing phosphorus, which comes from fertilizers and city wastewater treatment plants. With treatment plants having been upgraded all along the river — including in Mankato and St. Peter — that source of phosphorus has been significantly reduced.
Still, Fisher said, much of the funding is being aimed at further improving Twin Cities metro area wastewater treatment and storm water storage.
“ The MPCA studies are calling for 1 percent of the problem to be fixed in the metro area for $850 million.
I struggle with spending that to fix 1 percent of the problem,” Fisher said.
“I understand they want everyone to do their part.
Politically, (farm) producers say urban areas need to do their part. I understand that.”
Fisher said he’d rather see metro-area cities and the state put some funding into upgrading municipal systems, but put a majority of the money into projects that reduce sediment loading and erosion along the river valley. One way to do that is to create systems that store water so it can be released more slowly into the rivers.
A project near Mapleton, for example, creates an overflow basin alongside drainage ditches. Other projects use farm tile drainage systems that, through a series of smaller tiles or mechanical gates, slow the rate of water draining from fields.
The mechanical tile systems are, however, more expensive to install and maintain and don’t work well on sloped farm fields.
The storage basins along ditches take crop land out of production.
Anything taking land out of row- crop production runs up against skyrocketing farmland prices. In fact, the amount of land in grass and vegetation is likely to lessen in coming years as it is pulled out of the Conservation Reserve Program. CRP pays landowners to keep environmentally sensitive land out of production for a set number of years.
Statewide, about 128,000 acres of CRP contracts will soon expire, while only about 33,000 acres were enrolled during the recent spring sign-up period.
In the next three years, more than 550,000 acres of CRP are scheduled to expire.
Conservationists believe much of that land won’t be re- enrolled in the program because of high farmland and crop prices.
Another partial solution, which does not take farmland out of production, is to shore up steep bluffs to slow erosion. On the Le Sueur River, crews are using a mixture of trees, sand and dirt to weave a protective barrier over the surface of steep bluffs and river banks. It’s similar to the traditional stone rip-rap but costs about three-fourths less.
Fisher would like to see more focus on similar projects in the Le Sueur and Blue Earth river basins — both of which contribute mightily to the sediment in the river.
“For less money we could target some higher-priority areas more intensely. We know, bluff by bluff, where the problems are. If we want to make an impact, why not take big chunks of money and hit those areas hard?”
Dennis Frederickson, a former Republican state senator from New Ulm who is now the Department of Natural Resources director of southern Minnesota, is known for his support of the river and keen ability as a conservative senator to get environmental projects approved in the Legislature.
“Certainly drainage off the landscape, from fields and other lands, is a contributor to some of that impairment,” Frederickson said.
“Agriculture is a huge economic factor in the Minnesota River watershed and the state, so what we do needs to make economic sense for the farmers and make sense for the river.”
Frederickson said everyone needs to focus on solutions that can make a difference rather than spending too much time arguing about fault.
“It’s important not to square off in issue groups or stakeholder groups one against the other. Every segment in society contributes to the impairment of the river. We need to spend our time and money determining how to improve those impairments instead of arguing about where the faults are.”
Frederickson said dealing with issues related to agriculture may be thorny but not impossible.
“ We’ve dealt with issues with herbicide and pesticide and genetics over the years.
Let’s use that same creativity to find how we can farm and raise the abundant crops we do without impairing the waters.”
While agriculture is a powerful economic and lobbying force, pressure from urban policymakers and those around Lake Pepin are increasingly calling for more regulation of agriculture drainage.
“ The question from urban residents is, why do we need to control anything more than an inch of rain off our landscape when the rural areas don’t have to?” Fisher said.
“ We have an urbanized Legislature that is pushing this more and more. The discussion is will there ever be a requirement for more water storage on the landscape. It would be huge amounts of land taken out of production,” Fisher said.
“It’s a fair question, but there are no easy answers.”