By Tim Krohn
Free Press Staff Writer
ST PETER — When the snow melts and rains come in the spring, tons of soil can be churned off of ravines and stream banks along Seven Mile Creek, located between Mankato and St. Peter.
With the recent installation of hard plastic liners in some of the steepest ravines coming into the creek inside Seven Mile Creek Park, environmentalists and county officials hope to cut the amount of sediment going into the designated trout stream, which empties into the Minnesota River.
“So much of the data is telling us that fast waters are eating away at the bluffs and blowing out the sides of these small tributaries like Seven Mile,” said Scott Sparlin, a New Ulm conservationist who’s long worked on water quality issues.
Working with the Friends of the Minnesota Valley and Nicollet County, and using state Legacy grant money, the plastic liner was installed in several channels. The SmartDitch product (SmartDitch.com) uses black plastic panels to line ditches or streams. The liner not only protects the bank by covering it, but is outfitted with deep ribs that slows the water flow as it enters the creek.
The Seven Mile project incorporated other techniques, such as installing rocks in certain areas to create pools that further slow water flow.
“It’s probably over-designed, but we wanted to see what happens and how well it works,” said Sparlin of the test project, which was installed by Ground Zero Services of Courtland.
The project can be seen by parking in the last lot at the park, walking across the bridge and taking the trail about 100 yards.
Friends of the Minnesota Valley was awarded an $80,000 grant from the state’s Legacy fund, which uses dedicated sales tax money for water quality and other projects. About $8,000 was spent on the Seven Mile Creek project.
Nicollet County is serving as the fiscal agent for the grant.
The rest of the grant will be used for similar projects in the park, but Sparlin said the hope is to use the bulk of the money to manage agriculture drainage near the start of the creek to slow the water flow into the creek.
“We’d like to go to the top of the basin where the water is coming in from the landscape and see if landowners would do a conservation drainage project to hold the water in the soil longer.”
A growing body of evidence is showing that more highly effective farm-field drainage systems are a big cause of bank and ravine erosion in the Minnesota River valley. The tile lines send too much water, too fast into rivers causing them to rise rapidly and run fast. The problem is causing sediment in the Minnesota River that is filling in Lake Pepin on the Mississippi.
There are conservation drainage systems that allow water to be drained off the top several inches of fields, but are then shut down to hold more water in the soil beneath.
“It makes water available for the corn and soybeans. If you had managed drainage in a dry year like this, you would have had water in the soil when a lot of people didn’t,” Sparlin said.
But the systems are complex and more costly than traditional drainage systems.
“We need to get elected officials and everyone to accept them and to incentivize them more. Farmers should be able to get a certain amount per acre to install them.”