KIMBALL, MINN. – The Clearwater River squiggled toward Hwy. 15, where Dennis Loewen perched on the rim of a box culvert midway down the embankment, lowering a modified snow rake into sluggish, chocolatey water.
At the end of the pole was an instantaneous flow gauge. Moving left to right, at each of 12 stops, Loewen, the Clearwater River Watershed District's assistant administrator, called depth and flow readings back to Cole Loewen, CRWD administrator and Dennis' son.
The river meanderings are man-made. The adjacent Kingston Wetland is altered. A man-made ditch, County Ditch 46, built in about 1916 to drain farm fields, is what led to the wetland alterations and, eventually, the re-meandering.
The Kingston Wetland restoration project, a five-year, $689,248 undertaking meant to clean up downstream lakes by boosting dissolved oxygen and cutting the amount of phosphorus entering the Clearwater River, officially wrapped up in September.
It's the first project in Minnesota to address low dissolved oxygen levels without removing a dam or wastewater treatment plant. A $354,282 U.S. Environmental Protection Agency grant administered by the Minnesota Pollution Control Agency helped pay for testing, design and construction.
Construction — including re-meandered river bends, a rock weir and a limestone filter berm — was finished in March 2013.
The wetland had been altered in the 1980s to divert particulate phosphorus. The ditch was broken where it entered the wetland. A diversion channel routed the river around the wetland; structures forced the water back into the wetland. It worked, bringing summertime total phosphorus levels from 400 to 40 micrograms per liter. Too much phosphorus promotes algae growth and, at the extreme, leads to fish kills.
But after 30 years, Cole Loewen said the wetland had started releasing soluble phosphorus back into the river.
From 2002 through 2008, the MPCA declared Lake Betsy plus five other downstream lakes in the Clearwater Chain impaired for aquatic recreation because of excessive nutrients. Phosphates in particular were blamed for murkier waters and more algae blooms.
Additionally, in 2004 the MPCA found the stretch between Clear Lake and Lake Betsy didn't meet minimum dissolved oxygen concentrations of 5 milligrams per liter. A 2009 study showed altered hydrology in the Kingston Wetland was a factor, and determined increased sediment was a cause. The sediment in the wetland was absorbing oxygen.
This project concentrated on the upper watershed, including the stretch from Clear Lake in Meeker County east to Lake Betsy south of Kimball.
The recommendation: Reduce the sediment oxygen demand by 60 percent, from 812 pounds to 325 pounds a day.
Now, high water levels send overflow into the wetland, which still removes particulate phosphorus. But when the water is low, it stays within the river channel. The diversion channel has been severed. Meanders increase the velocity. The limestone berm filters out phosphorus.
The end result: a reduction in the amount of soluble phosphorus released and carried downstream plus improved dissolved oxygen levels.
The first two years of post-construction test results show the Kingston Wetland Restoration Project is working. Phosphorus, nitrate and dissolved oxygen levels have met project goals. Because flows have remained low, dissolved oxygen remains an issue.
Before the restoration, 69 percent of downstream dissolved oxygen readings violated state standards. After: 27 percent violated standards. Twenty percent less phosphorus was released to Lake Betsy, the first lake downstream from Kingston Wetland.
Phosphorus levels above and below the wetland have evened out — showing the wetland is releasing less soluble phosphorus.