A Glacier, A Lake, A Valley
and Soil for the Future
University of Minnesota Report, May 1979
by William Hoffman
At the close of the age of glaciers, about 11,000 years ago, a vast lake stretched across the heart of North America.
The lake was formed by a great continental ice sheet as it melted and removed northward, and the lake was so big that its remnants--Red Lake, Rainy Lake, and Lakes Winnipeg, and Winnipegosis--together with the Great Lakes--might well fit inside it.
Part of the lake reached down into the United States, in the vicinity of the Minnesota-North Dakota border. When ancient Lake Agassiz drained, it left behind traceable shorelines and a nearly flat valley.
Today that valley is one of the most fertile and protective on earth. The river that divides it, the Red River of the North, "the American Nile," is once again within its banks after a spring flood that caused millions of dollars in property damage and left untold tons of rich topsoil in roadside ditches. It has been tabbed the valley's worst flood of the century.
People of the Red River Valley are hardly unaccustomed to spring flooding. The valley's first settlers, a group of small-time farmers who had been forced off their land in Scotland, were nearly washed away by the severe flood of 1826. A quarter century later, high waters brought about a major relocation movement to higher ground.
Not until near the end of the 19th century was the valley's drainage problem first addressed by the Minnesota Legislature, and not until after World War I was a comprehensive drainage system in operation.
The Red River Valley's unique geological past, its topography, soil, and climate, set it apart from the open prairie to the west and the forested lake country on the east.
The valley is 320 miles long and about 50 miles wide, but it drops only 260 feet from south to north and rises only two or three feet a mile for the first 10 to 15 miles on either side of the river. It is so flat that its lateral ascent from the river's banks is imperceptible to the eye.
The river itself was once miles wide as it ran northward through the bed of Lake Agassiz. As it decreased in width through the centuries, it deposited heavy layers of fine silt along its course. This alluvium ranges in depth from 5 to 60 feet and lies over a variegated mass of silt, sand, clay, and gravel known as glacial till.
Rich soil, a flat plain, and substantial rainfall combine to offset a relatively short growing season and make the Red River Valley prime country for raising sugar beets, potatoes, corn, onions, grains and grasses, and sunflowers, now a boom crop in the region.
But some soil experts fear that the valley's natural advantages are being threatened by poor conservation practices and the lack of an effective and comprehensive flood control plan.
One of those experts is John Polley, assistant professor of mechanized agriculture at Crookston. As a former official of the Soil Conservation Service in the valley, he knows about its special problems of soil erosion and water drainage.
Most soil conservationists agree that four or five tons of soil per acre is an affordable loss, for about that much is naturally generated each year. But wind and water combine to erode eight to ten tons of the valley's rich topsoil annually, Polley said.
"Soil is being lost at a greater rate than it is being replaced, even though topsoil is exceptionally deep here," he said. "But farmers still aren't noticing. Their main consideration is what they think is most economical--until the shoe starts to pinch."
Soil loss from high and constant wind is considerable. "The flatter the surface and the greater the length of the open field, the greater the length of the open field, the greater the problem of wind erosion," Polley said. In potato and sugar beet fields, wind erosion is especially bad, he said.
Yet farmers continue to remove shelter belts and windbreaks because "long, flat surfaces are necessary for today's farming equipment." Equipment that used to be 10 to 20 feet wide is now 60 feet wide, and the fewer obstacles in the field, the easier machinery is to maneuver.
The apparent dilemma of modern farming methods versus soil loss from wind erosion is not universally credited. "Recent studies argue that wind erosion isn't as bad as first thought," Polley said. "They say shifting winds merely blow the soil back and forth."
But if the soil loss from wind erosion is less than first believed, loss due to water continues to be substantial, especially during serious flooding. Hundreds of farmers are seeking federal assistance for damaged fields and equipment in the wake of this year's flood.
Polley said that, in an ordinary spring, snow will melt first in the fields, a week later in the grasslands, and two weeks later in the wooded regions, allowing for gradual drainage. "This year all the snow melted at once--plus it rained," he said.
To add to the problems of fast runoff, many farmers are no longer plowing in the fall, and many have filled in potholes in their fields where water used to collect. Polley figures filling in potholes has increased runoff about 5 percent, "not as much as some people think."
Not only is the valley extremely flat, but the soil doesn't hold water very well, Polley said. "It is quickly saturated and flows like oil, ending up in ditches and estuaries." Fertilizer in agricultural runoff finds its way to the Red River and eventually to Lake Winnipeg, where it fosters the growth of plant life and "leaves the lake looking like pea soup."
Polley is convinced that an effective flood control plan must include manmade lakes and floodplains where river headwaters can be diverted and impounded. One successful project in the valley has incorporated flood control, recreation, and wildlife protection, he said.
But a comprehensive plan will require use of private land for the purpose of flood control. "Few if any farmers would go for that," Polley said.
"In Pennsylvania the water problem is handled through a special watershed fund to compensate landowners whose land is used for flood control. They have an effective plan in operation, and I think we could learn a lot from it," he said.
Meanwhile, as federal, state, and local agencies study the valley's drainage problem, Polley teaches his students, many of them the region's future farmers, that over the long run the most economical farming is that which preserves its own foundation, and that sound flood control and soil conservation practices go hand in hand.