This article originally appeared in Working for Clean Water: 2015 Iowa Watershed Successes
Once, the marsh supported waterfowl hunting, fishing and other recreation, including a boat livery and beach. But over the years, sediment from surrounding fields created silt plumes that flushed into the main lake during heavy rains, hidden by cloudy lake water. Then two events in 2002 set the marsh on a new course. First, the DNR and Lake Improvement Commission began dredging the main lake and second, Little Storm Lake was identified as a marsh in need of fixing.
It wasn’t long after the water quality began to improve when it became evident just how much silt was entering the lake. About 70 percent of the water entering Storm Lake from its 54-1 watershed-to-lake acreage ratio is delivered by Powell Creek via Little Storm Lake marsh — and Little Storm Lake was not functioning like a healthy marsh.
"Silt plumes were stretching halfway across the lake. It was really apparent after we started cleaning up the big lake," says Kruse. "It was evident how much silt we were putting into the lake."
The Storm Lake Preservation Association developed a marsh restoration proposal, helping it secure funding from WIRB and DNR. In 2008, the City of Storm Lake pledged its support, Ducks Unlimited signed on to provide engineering and design work for the marsh, with the Storm Lake Improvement Commission, Lakeside, Storm Lake Preservation Association and the DNR contributing to the effort, too. The group wanted to address the potential impact of backing water onto neighboring properties.
"We (DNR) have a very limited footprint in the area and a flat landscape," says Julie Sievers with the Iowa DNR’s Storm Lake office. "We have the Lake Creek Country Club and homeowners association in the watershed and two private landowners on either side that we needed to factor into the plans."
The marsh redesign needed to slow water moving through the system with a way to bypass the marsh if necessary. Step one was to separate the marsh from the lake and Powell Creek by building a 4,000 foot dike with the ability to direct the creek water through a winding channel designed to slow its movement, enter the marsh, return to Powell Creek and finally Storm Lake – free from silt and nutrients. Barriers were added to prevent carp from accessing the marsh. Slowing water allows silt particles to separate from the water, where vegetation can use the nutrients trapped in the silt.
But designers needed flexibility to get water out of the marsh quickly. A pump sends water to a new sediment basin, where it slowly trickles through vegetation and back to Powell Creek before entering the lake. In flood events, the dike was designed to be overtopped to protect its integrity.
"This system was designed to allow periodic draw downs that will solidify sediment and promote emergent and submergent vegetation and kill any carp that got in to the marsh," says Pete Hildreth, southwest Iowa supervisor for the DNR’s Wildlife Bureau.
Construction began in 2010. In 2012, the pump was turned on to dewater the marsh. In 2013, an 11-inch rain over Memorial Day Weekend sent water over the dike, but caused only minimal damage, just as designed. Little Storm Lake is now ringed with 7-foot-tall cattails and serves as a teaching tool to local students, thanks in part to students at Buena Vista University who placed a series of educational panels along a trail and floating dock extending into the marsh.
Improving water quality was the driving factor, but it also created excellent waterfowl habitat. On just one spring day, Kruse saw 12 waterfowl species along with kayakers, wildlife watchers, walkers and bikers using the area.
