The citizens of Minnesota spend $90 million each year to slow runoff from farm fields and other lands that are filling their lakes and rivers with nutrients and sediment. If where you put your money shows your true priorities, water is clearly important to people in the Land of 11,842 Lakes.
So it’s natural that how the investment is paying off is a big question. By most measures, it’s not. After decades of work and millions of dollars, many of Minnesota’s rivers still run brown and its lakes still turn green. Almost 100 new waters were added to the state’s impaired list in 2014 for excess nutrients. Why?
The St. Croix Watershed Research Station is in the middle of an ambitious study to understand the complex answer to that big question.
Uphill battle, downstream problems
The 2008 Legacy Amendment is responsible for much of Minnesota’s water quality budget. The $535 million allocated to clean water since it passed has funded hundreds of projects big and small across the state. It’s paid for catch basins to filter out sediment, grassy waterways in farm fields, rain gardens in residential areas, wetlands and prairies recreated wherever possible.
But still: brown rivers, green lakes.
The reason could be any number of things, and it probably is. Perhaps more corn and soybeans are being planted, creating conditions prone to runoff. Maybe the bizarre early effects of climate change, floods and drought, are to blame. Maybe it’s that only some of the projects are deployed correctly. Perhaps there still hasn’t been enough work and money. Perhaps we’re still paying for past mistakes. Or maybe we don’t have the right information.
While the projects that have been implemented on the ground can be pretty easily quantified, they aren’t the ultimate measures of success. The goal is improving the health of Minnesota’s lakes and rivers. Are they getting any cleaner because of better land management?
Surprisingly little long-term information is available to answer that question. The longest water quality monitoring record in the state is for the Minnesota River at Mankato. It only goes back to 1978 and it shows no change. Four decades of data is too short to show clear trends, anyway. Watersheds are complex systems of land and water, where geology, vegetation, human land use, weather, and many other variables affect what ends up flowing downstream.
It may be that Minnesota needs to wait longer to see improvements, or it might be that the state needs to look again at how it spends water quality funds. The research station’s experience in reconstructing the history of watersheds puts it in a unique position to help identify the most effective uses of taxpayer dollars – and the best ways to protect lakes and rivers that Minnesotans love for swimming, fishing, drinking, and wildlife habitat.
Ice-fishing for mud
On a relatively warm day this past January, a team of paleolimnologists trekked onto Miller Lake in Carver County, in the Minnesota River watershed. From shore, it might have looked like they were ice fishing. They had augers, warm clothes – and long plastic tubes. They didn’t have any rods or tip-ups, and they were fishing for mud, not crappies. They wanted to look back in time.
Over the course of five hours, the team drilled through the ice at four sites around the lake, pre-selected based on topographic maps of the lake bottom, then pulled up columns of brown stuff containing stories about what the lake was like centuries ago.
As the sun warmed the ice, the lake groaned and moaned underfoot. The researchers did a complex dance as three people at a time pushed several meters of rods and tubes through holes in the ice, and then pulled them back up to retrieve the sediment cores.
The columns of mud, sliced and analyzed in the lab, will tell the researchers if the water is cleaner today.
“Without this data, we can’t know if all the work is improving water quality,” Engstrom said.
Six feet of mud on the bottom of these lakes can represent hundreds or thousands of years. Each year, another layer of soil, weeds, algae, and even the occasional fish bone is deposited. The chemistry of those layers can tell us much about the lake's historic conditions, from nutrient loads and algae species to even the source of the sediment, and by looking at several different aspects of its ecology, a detailed picture of the lake’s history, and the surrounding country, its history emerges.
Digging through the cores back at the lab would be a little like astronomers looking through giant telescopes to see galaxies billions of years old.
Miller Lake looks like many prairie lakes. It is in a shallow bowl, surrounded by low hills hosting corn fields, a horse farm, and hardwood forest. It seems at first glance like one of Minnesota's many other shallow lakes that grow a lot of algae. But it is a uniquely important lake for the study because it has a substantial stream feeding it and flowing out.
The creek carries the soil and nutrients from a 70-square mile watershed, and as it passes through the lake, much of that material settles in fine layers on the lake bottom. It is an ideal archive of everything that has happened upstream for hundreds of years. The station picked this lake because it would tell a fairly clear story about what has happened in its entire 70-acre watershed.
As the team did its measurements and diagrams and collected core samples at the third site, research station director Dan Engstrom walked over to where Miller Creek rushed out of the lake and out of sight around a bend, singing its ancient song. Between icy banks, it flowed clear over a rocky and sandy bottom. It was easy to see why rivers don’t lay down sediment like lakes, which is why Miller is so valuable.
Using the snow on an ice ledge as a chalkboard, Engstrom drew with a stick to illustrate the term “knick point,” where a tributary stream abandons its slow pace across flat uplands and cuts down the broad bluffs of the Minnesota River Valley.
This ancient geology and modern human behavior have combined to cause increased erosion into the river. Stream bank erosion in the Blue Earth River basin of southern Minnesota.
“The Minnesota River’s gorge was created by a massive flood which drained Glacial Lake Agassiz 10,000 years ago,” Engstrom explained. “It created bluffs where slow prairie rivers pick up speed as they flow into the Minnesota. Now, we are adding more water, because of drain tiles and parking lots, and precipitation patterns are changing, and that’s widening the river, eroding the banks, and sending more soil downstream.”
What we know now
The work has already added one key piece of knowledge to our understanding of Minnesota’s lakes and runoff: sediment is accumulating on the bottom of Minnesota lakes in farm watersheds three to six times faster than natural, pre-settlement periods.
“The bottom line is, we are not very far down the path to clean water,” said Shawn Schottler, senior scientist. “The data says there has been no improvement in many places.”
Despite heroic efforts to improve farming practices, it’s possible the protections are just overpowered by economic pressures. Between 2008 and 2012, Minnesota lands enrolled in the federal Conservation Reserve Program, which pays farmers to keep sensitive lands out of production, dropped by 425,000 acres, or roughly 23 percent.
It’s possible that water quality work is like the Battle of the Alamo: While each Texan surely fought heroically, they were simply outnumbered and poorly deployed against Santa Anna. If there had been more troops, or they had a better strategy, perhaps they could have prevailed.
For Minnesota’s water, it may be time to do more and do it smarter, or watch our lakes go the way of Texas.
Funding for this research was provided by the Minnesota Environment and Natural Resources Trust Fund as recommended by the Legislative‐Citizen Commission on Minnesota Resources (LCCMR).