Minnesota taxpayers and anglers have spent millions of dollars realigning dozens of streams and creeks across the state to stop erosion, clean up the water and bring back trout and other aquatic life.
Now it's time to find out how well those projects actually worked.
A team of researchers out of Duluth will evaluate several trout streams that underwent major restoration work over the last decade. They intend to find out if those projects not only brought back trout and the water bugs they eat, but also whether the realignment met some loftier goals, such as slowing erosion and holding up against heavy rains and floods.
Perhaps most importantly, the state needs to know if realigning creeks has upset their natural connection with groundwater or if it has unintentionally made some problems worse, said Valerie Brady,aquatic ecologist for the University of Minnesota Duluth Natural Resources Research Institute.
"When you do these big, earth-moving type projects, you stand the chance that it can really muck up that stream's connectivity with the groundwater," Brady said. "We haven't been able to measure for that before. So now that these places have had some years to recover, we can see if things did get better, or if they accidentally made anything worse."
Erosion, the root problem forcing major restorations, isn't going away anytime soon. More streams will be realigned in the coming years as they continue to wash away land near homes, roads, bridges and businesses.
The look of the clear, fast and picturesque streams in the woods of northeastern Minnesota can belie their sometimes tenuous conditions. Most of the state is made up of sandy soil or limestone, which can quickly absorb rainfall from even heavy storms. But northeastern Minnesota is made up of a clay that was likely hardened over eons under an ancient lake, Brady said.
"It's all bedrock and clay, and streams rise quickly when it rains," Brady said.
When Minnesota was settled, the stormwater problem compounded. Trees were cleared, and farms, roads and homes were built. Ditches were dug to shoot water away from development. All of that has pushed more water through the system.
"Now we have these smallish streams getting all kinds of water that the channels can't handle at that volume and speed," Brady said. "So these streams are trying desperately to realign their banks and expand their channels, but we won't let them because it would eat a road or wash out a bridge."
Storms have also been getting harsher and are happening more often because of climate change.
Over the past 20 years, the state has addressed the problem by realigning dozens of creeks, including Knowlton and Sargent creeks in Duluth and the Stewart and Little Stewart rivers to the north. Streams have been directed away from roads and homes and cut into more natural meandering paths, which can slow water flows. Their shorelines were also buffered with gentler slopes that don't erode as quickly.
But Minnesota's streams have always been closely connected with its groundwater. Much of the life within the streams depends on that clean and cold groundwater springing in. It's possible that realigning the creeks can cut off their connection to the groundwater, leaving them warmer, murkier and more lifeless, Brady said.
The timing is perfect to evaluate the restorations, most of which have happened thanks to money raised from the Legacy Amendment that voters approved in 2008, said Doug Dieterman, a DNR research scientist.
Roughly 80 restoration projects, using a variety of engineering techniques and habitat designs, have been completed over the last 20 years in southeastern Minnesota alone, he said. Many more will be done before the Legacy Amendment sunsets in 2034. Enough time has passed to get an accurate sense of which of types of projects are holding up, and which aren't.
"The big question is to find out why one might not be holding up," Dieterman said.
The work by the northern Minnesota researchers will be funded from the state's Environmental and Natural Resources Trust Fund and take about four years to complete. The group will focus on up to seven streams near Duluth and in the Arrowhead region, but hasn't selected them yet. It's important to find creeks that have untouched stretches to get an accurate sense of how much groundwater should be flowing into the realigned leg, Brady said.
She said she expects the findings to be complex, but telling.
"This will give us an in-depth look that these system haven't had in Minnesota," she said. "The big question is can we help figure out ways to do it better if there is an issue."