Aquatic harvesting next step in lake restoration
October 18, 2013
A coalition of local governments and community groups in Lake View will soon be the proud owners of a new aquatic vegetation harvester.
The machine will be used to remove excess vegetation from Black Hawk Lake to keep the water open for recreational boating, said Lake View city administrator Scott Peterson.
The Iowa Department of Natural Resources will purchase the machine for use starting next spring if it is operated and maintained by a local entity or partnership of local organizations, said Peterson. The Lake View Community Club has already made a commitment to participate. Peterson expects the City of Lake View to get involved, as well as Sac County and the Black Hawk Lake Protection Association.
According to Ben Wallace, fisheries biologist with the DNR, cost of the machine will be just less than $250,000, including some accessories and shipping charges. There is one other machine of its type in use in the state, at Carter Lake. Based on that experience, Wallace believes the cost of maintaining and operating the machine will cost the local coalition about $2,200 per month.
The aquatic plant growth exploded this summer after removal of the lake's fish last year. Rough fish, like carp, swim through the much at the bottom of a lake, constantly keeping sediment stirred up in the water, explained Peterson. Removing the fish removed the sediment, allowing sunlight to reach the lake bottom, boosting vegetative growth. The 922-acre lake was restocked with high-quality game fish, he added.
"The water is clearer than anybody recalls," said Peterson. "You just have to have different ways to handle different issues."
Removal of the fish was one significant step in a lake-restoration process that will take several years, said Wallace. A common management tool, last year's drought conditions allowed the DNR to save money and made the process very effective, he added.
With the cooperation of adjacent landowners, a coordinated effort led by the Soil and Water Conservation District has also made "significant improvements" to the Black Hawk Lake Watershed, such as developing terraces, designating no-till areas and planting cover crops. The goal is to manage nutrient runoff and reduce the amount of phosphorous that reaches the lake.
"Just like corn or soybeans, aquatic plants need phosphorous and nitrogen to grow," explained Wallace. "The best long-term strategy for aquatic vegetation management is nutrient management. The machine is a tool to get through the years while achieving that goal."
Hopefully, the machine won't be needed five to 10 years down the road, he added. Wallace stressed that aquatic growth is not bad unless the nutrient levels are out-of-balance.
"Aquatic vegetation is a good thing; it helps keep the water clean, reduces wind and wave erosion and feeds the fish," he explained. "You want a healthy balance of open water with some areas of vegetative growth."
Wallace said that the majority of the growth in the lake this year will die over the winter season. The machine will start being utilized in April or May of 2014. The frequency of machine use will depend heavily on the weather.
"It's easier to get in on the early end," he said.
The machine essentially floats on the water, cuts the vegetation down and carries it to a truck to be removed, said Peterson. It has to be removed from the site. If the vegetation was cut and left in the water, it would eventually break down, and could cause full algae blooms, said Wallace. Algae blooms grow on the water's surface, blocking sunlight and inhibiting the growth of the good aquatic plants. If an algae bloom grows too large, there will be on oxygen deficit when the growth dies that can kill the fish in the lake.
Wallace said that the City of Lake View and the DNR are currently exploring disposal options. The aquatic growth is all organic matter. Nutrient concentrations are difficult to determine, but the majority of the matter is water, he added.
The lake restoration process began with local interest that led to water-quality studies and grant applications. The support of local businesses and residents has not only made the work more enjoyable but has contributed to the project's progress, said Wallace.
"There are a lot of eyes on (the Black Hawk Watershed) right now, and people all over the state are looking at what we're doing here," he said. "A lot of it is because of the local leadership and cooperation. Lake restorations are big undertakings that take several years."
For Peterson, the effort is well worth it. According to a Center for Agriculture and Rural Development report, the lake brings about 250,000 visitors who contribute $19.05 million annually to the local economy. Black Hawk Lake also sustains 379 jobs with an annual payroll of $5.09 million.
"It's nice to put a number to it, but everyone generally knows the number of people (the lake) brings in and the money that comes with them are extremely important to the local economy," he said.
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