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Watersheds are mini-Mississippi Deltas

By Janet Kubat Willette
jkubat@agrinews.com

Date Modified: 11/21/2012 1:05 PM

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RICE COUNTY, Minn. — Gary Wagenbach drove his pickup in the road ditch to illustrate a point.

The road ditch, which had only recently been cleaned, was once again filled with sediment.

Most of it happened this spring, Wagenbach said during a Rice County Conservation Tour held last month.

Rice County received 3.82 inches of precipitation in April, 8.07 inches in May and 6.8 inches in June, all before the corn and soybeans were large enough to hold the soil in place.

It's a mini-Mississippi Delta right in their midst, explained Wagenbach, a Carleton College emeritus professor of biology, science, technology and society who is also a Rice County Soil and Water Conservation District supervisor.

Sediment moved with rushing water from the top of Prairie Creek Watershed to the lower portion, settling as the water slowed.

The soil that settled in the lower portion of the watershed was mostly silt, Wagenbach said. Silt describes the particle size. Silt is smaller than sand and larger than clay. It's smooth like cake flour and highly mobile, hence highly erodible with wind and water when not protected in some way.

"It just wants to move, it's easily carried by water and wind," he said.

During one particular precipitation event this spring, a sheet of water topped the road for a distance of about 75 feet, Wagenbach said. From there, the water continued to move downslope across a field enrolled in the Conservation Reserve Program that abuts a branch of Prairie Creek. It was a real soup, he said, with residue, water and soil mixed together as it moved, filling the ditch with sediment and plugging the culvert before moving further down in the watershed.

A leaf and its veins are a good visual metaphor for a watershed, Wagenbach explained. The veins are where the water travels through the land in the watershed. Then, we carve up the land like a pan of brownies to make fields out of it.

That's where conservation programs come in.

Rice County's Soil and Water Conservation District staff as well as staff from the Natural Resources Conservation Service in Rice County have information about incentive-based programs designed to encourage landowners to put the best practices in place on their land to hold their soil in place. They work with rural and urban landowners, he said.

If water is involved in any way, the SWCD has the capacity to provide legal, technical and engineering advice to make sure the highest standards are maintained.

As a SWCD supervisor, he said he'll talk to anybody who's interested in learning more about conservation and the cost-share programs available to landowners. His main role, though, is to provide legal and financial oversight of the Rice County SWCD. There are five supervisors in the county and supervisors are elected during the general election.