Black Hawk Lake in Sac County covers 922 acres and drains into the Raccoon River, which flows into the Mississippi River. The southern-most Iowa lake formed by a glacier, Black Hawk Lake attracts more than 250,000 visitors annually.
“A lake is a reflection of its watershed,” said Ben Wallace, an Iowa Department of Natural Resources (DNR) fisheries biologist. “Concerns about water quality prompted the community to look at various solutions.”
The process started when local leaders commissioned Iowa State University (ISU) to conduct a two-year study of the water quality in Black Hawk Lake, as well as land-use practices in the surrounding watershed.
“We found we needed to reduce the phosphorus load by 80 percent,” said Wallace, who noted that restoration work began after ISU completed its study in 2010. To reach this goal, local leaders are taking a multi-pronged approach, including:
Dredging. Starting in the summer of 2016, a dredging project will begin removing 320,000 cubic yards of sediment from Black Hawk Lake.
Increased agricultural conservation. Many local farmers are participating in the Black Hawk Lake Watershed Project. Through a combination of conservation practices, including livestock nutrient management, no-till and conservation tillage, a Conservation Reserve Enhancement Program (CREP) wetland and streambank stabilization, hundreds of tons of sediment and thousands of pounds of phosphorus have been prevented from entering Black Hawk Lake in recent years.
"This is a win-win for everyone,” said T.J. Lynn, coordinator of the Black Hawk Lake Watershed Project.
Homeowner cooperation. Many Lake View residents use phosphorus-free fertilizer on their lawns. Soil samples pulled by the local FFA chapter in the past few years revealed ample nutrients in homeowners’ yards.
“Everyone can play a role in improving water quality,” said Scott Peterson, Lake View’s city clerk/administrator. He encourages people to participate in IOWATER, Iowa’s citizen volunteer water monitoring program.
Businesses and municipalities. Lake View plans to install a large bioswale, a landscape element designed to remove silt and pollution from surface water. runoff In addition, the City of Lake View is working with Evapco Inc. in Lake View to install a permanent wetland on the manufacturing company’s property to help enhance water quality.
Rough fish removal. Since rough fish like carp and gizzard shad degrade water quality, the DNR depopulated the fish out of Black Hawk Lake a few years ago and repopulated it with more desirable species like bluegill, crappies, large-mouth bass, yellow perch and walleye.
Improved water clarity. While the average clarity in Black Hawk Lake was only 6 inches in 2012 before the rough fish were removed, it has increased to 6 feet, said Wallace, who added the goal is to create water clarity that’s at least 4.5 feet deep.
Vegetation management. Improved water clarity creates more vegetation in the lake, including some plants that grow to the surface of the water. The DNR uses a vegetation harvester to control the plants, which can get tangled in boats. “It’s a delicate balance to manage a dynamic system like a lake,” Wallace said.
Shoreline armoring. Physical structures have been installed to hold shorelines in place and protect them from erosion.
Partnerships. Up to 13 entities have been involved in protecting water quality in Black Hawk Lake. “It takes partnerships to improve water quality,” Peterson said.
Measurable progress. Phosphorus loads in Black Hawk Lake have dropped by 35 percent so far. The lake now includes a more balanced ecosystem and greater biodiversity, from freshwater sponges and mussels.
“It takes time to turn things around, but a lot of good things are happening,” Wallace said. “People love this lake and want to do everything they can to protect water quality.”
Maulsby is a freelance writer from Lake City.
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