New effort aims to hold back water to slow ‘flashy’ Minnesota rivers
Most of Minnesota is in a dry period now, but wet years happen, too. "Flashy” flows, as scientists call them, are an increasing problem in the Minnesota River valley and elsewhere in the state.
MANKATO, Minn. — Sixteen years ago, Don and Becky Waskosky moved to what they thought was their dream home in the country outside of Mankato.
They were drawn to the quiet, the birds and wildlife — and breathtaking views of the Le Sueur River as it winds through towering sandy bluffs.
This year, the river is the lowest the Waskoskys have ever seen, due to the widespread drought . But in past years, heavy rains have caused the river to suddenly swell into a torrent, carving away steep banks, and washing sand and silt downstream.
In 2016, their neighbor had to abandon his house when the river tore into the bluff and threatened to send the structure tumbling down the bank. The couple spent sleepless nights worrying that their home would be next.
“It just roared through those trees, because so much water was going so quickly,” Don Waskosky said.
The Waskoskys’ house survived, but over the years, their backyard has disappeared. A deck is now just a few feet from the steep edge.
The Waskoskys wondered where so much water was coming from. They noticed how quickly the river would rise after it rained.
"If we get an inch of rain, it'll go up a foot overnight, that fast,” Becky Waskosky said. “So when you think about getting 5 or 6 inches of rain, how much that river goes up — 6 feet. It’s jaw-dropping.”
Most of Minnesota is in a dry period now, but wet years happen, too. "Flashy” flows, as scientists call them, are an increasing problem in the Minnesota River valley and elsewhere in the state. Scientists attribute them to more intense rain events and the loss of wetlands that act as natural sponges.
The Le Sueur winds more than 100 miles through south-central Minnesota before it joins the Blue Earth River, which flows into the muddy Minnesota.
Most of the Le Sueur's watershed is farmland, drained with a system of tiling and ditches. As a result, water is moved off the land and downstream more quickly.
"We really just need to slow that rapid pulse of water that reaches the streams and is so erosive,” said Carrie Jennings, research and policy director for the St. Paul-based nonprofit Freshwater. "Often, that's followed by a really low-flow period too. So we end up with these streams that are very flashy — very high highs, very low lows."
All that water carries sand, silt and nutrients. The Le Sueur is a major contributor of sediment to the Minnesota River, which eventually joins the Mississippi just south of the Twin Cities.
Studies have shown the amount of water in the Minnesota River has doubled in the past 80 years. Sediment is flowing downstream to the Mississippi and filling in Lake Pepin at an accelerated rate.
New focus on slowing water
About 15 years ago, research started to point to a different source of sediment, Jennings said. Instead of primarily washing off farm fields, it was coming from the eroding banks of the rivers and streams.
“That means ravines that were lengthening, rivers that were widening,” she said. “That was a result of increases in water in the rivers themselves.”
Those higher flows are likely caused by the extensive farm drainage systems that speed up the delivery of water to streams, as well as large rainfalls occurring more frequently.
Jennings and other scientists believe that reversing this trend requires finding ways to hold more water on the land longer, so it doesn't rush so quickly into streams and rivers.
"If we can figure out ways to store more water in the landscape, and more slowly release that like the wetlands used to do, we're going to really improve these watersheds,” said Kimberly Musser, associate director of the Water Resources Center at Minnesota State University, Mankato.
Funding help for landowners
Last month, Minnesota lawmakers helped jump-start that effort by including $2 million for a water storage program in the two-year environment budget bill, which Gov. Tim Walz signed into law.
The funding will go to the state Board of Water and Soil Resources to provide financial assistance to landowners in the Minnesota and lower Mississippi river basins.
They'll be able to choose from a range of options to increase water storage on their land — such as restoring a wetland or planting perennial cover crops.
“Usually, it's better to hold the water higher up in the watershed, closer to the source,” said John Jaschke, executive director of the Minnesota Board of Water and Soil Resources. “Usually the less expensive it is, the more options you have.”
Scientists say storing more water on the land not only slows flash flows, but also reduces nutrient pollution and improves water quality.
“Nitrate transport is really closely linked to runoff and precipitation,” said Jacques Finlay, a professor in the University of Minnesota’s Department of Ecology, Evolution and Behavior. “The more water you move through a fertilized watershed, the more losses you incur.”
Finlay was co-author of a recent study that found that constructing and restoring wetlands along waterways is the most cost-effective way to reduce nitrate and sediment loads in large streams and rivers.
Supporters say those measures provide other benefits as well, such as wildlife habitat, healthier soil and more opportunities for recreation.
Musser said she's heard from people who used to canoe or kayak on southern Minnesota rivers, but don’t anymore.
"Now, because of the downed trees and the flashy flows, they say, ‘We're afraid to take our kids down there because it feels unsafe,’” she said.
‘We want to stay’
With the Le Sueur so low this year, the Waskoskys have been sleeping a little easier. But they worry about what future years will bring.
They’ve become vocal advocates for the concept of increasing water storage, telling their stories to state policymakers and anyone who will listen.
They hope it will benefit not just the Le Sueur, but other Minnesota rivers affected by human activity — and a changing climate.
"Because there's farmers losing fields, and people losing houses, their livelihood,” Don Waskosky said. “This is our retirement. And we want to stay here."