Paradise Lost, phosphorous contributes to ecological perfect storm
May 29, 2011
By Nancy Turyk & Chris Arnold
Sediment flowing directly into Park Lake after heavy rain in June 2008. Manicured lawns engird much of the lake. Stormwater runoff carries eroded sediment, as well as lawn-care fertilizer and chemicals, directly into the water, where each contribute to algal growth. ~photo Chris Arnold
Bob Lambert still remembers when Park Lake in Wisconsin’s Columbia County was known for its healthy fishery. When he was a kid in the ’60s, Park Lake was a hot spot for fishing. Lambert can remember going with his dad and grandfather and always catching a lot of fish. People would even come for bluegills, he said. “There was plenty of action from crappie, perch, once in a while northern, and the elusive walleye.”
But in the 1970s, the 312-acre lake started to change.
Aquatic plant growth that clogged boat motors made fishing difficult. By the mid ’80s, the proliferation of aquatic plants united a group of property and business owners and the nearby city of Pardeeville, who started to fight back. They formed the Park Lake Management District and attempted to curb the nuisance growth through harvesting and herbicides.
It shouldn’t have been surprising that Park Lake—a flowage created by humans in 1856 by the damming of the Fox River—would promote aquatic plant growth. It’s shallow and its rich sediments provide a perfect aquatic plant environment. The real surprise came around the turn of this century when the aquatic plants disappeared—replaced by algae.
By 2001, the algae grew so thick that light no longer penetrated into the water, killing more aquatic plants, whose detritus provided more nutrients for algal growth. A vicious cycle of ecological transformation had begun. Over time, even the more sensitive aquatic insects, such as mayflies and caddis flies, were replaced by pollution-tolerant lake flies and sludge worms.
Scientists and resource managers suspected that the algae proliferated due to a “perfect storm” of factors affecting Park Lake: the aquatic plant manipulation by humans, the unintentional introduction of bottom-disturbing fish like shad and carp, and a significant inflow of nutrients and sediments which enter the lake from the Fox River.
One of those nutrients is phosphorous.
Eerily reminiscent of clogged arteries prior to a heart attack, this map shows the 172 lakes and streams in Wisconsin that are on the Impaired Waters list as of 2010. Test results from these waterways exceeded the state standards for phosphorous and have led to biological problems. Once a waterway gets on this list, the state is required to develop a strategy for improvement. Park Lake and its tributaries are shown in the inset. ~maps courtesy the Center for Watershed Science and Education, UW-Stevens Point
Water Quality Follows Land Use
Most of the phosphorus entering the lake runs off the land. In the Park Lake watershed, 78 percent of the land is agricultural cropland or pasture. Across the 34,432 acres that drain into the lake, there are 26 farms raising 1,920 dairy cattle and 21 with 1,612 beef cattle—not to mention 401 hogs and 181 sheep. This livestock generates an estimated 5,780,245 gallons of manure annually.
At this farm in the Park Lake watershed, manure was being stacked in a hole in the ground that had a spring in it. Runoff travels into the road ditch, then into a culvert and straight to the tributary. ~photo Chris Arnold
While farmers stockpile manure for use as fertilizer, it doesn’t all stay piled up. When it rains or if not adequately contained, manure can—and does—run off into streams that feed Park Lake. The accumulation of manure in the watershed has actually overwhelmed the ability of the wetlands to soak up the phosphorus.
Another source of phosphorus was lawn fertilizer. Although only 1.2 percent of the Park Lake watershed is developed, much of this property is close to its shore. Removing shoreline vegetation buffers and chemically treating green lawns has translated to lots of fertilizer flowing directly into the lake.
Based on decades of research that recognized its harmful effect on aquatic communities, the state of Wisconsin in 2010 enacted a statewide ban on fertilizers containing phosphorous. However, Governor Walker’s proposed state budget would change these phosphorus rules, which could jeopardize the future of lakes like Park Lake, which, for its high concentrations of phosphorus and suspended solids, was added to Wisconsin’s list of Impaired Waters in 2006.
Education & Action
The Park Lake Management District realized their lake’s problem was getting too big to solve by citizen action alone. So in 2001, the district contacted Kurt R. Calkins, director of Columbia County’s Land and Water Conservation Department.
“Early on it became evident we had to bring in experts to help people understand the current state of the system,” Calkins recalled. A collaborative process emerged that led to water-quality monitoring, a watershed inventory of land management practices, and the development of a citizen-based plan for the lake.
In 2007, the Wisconsin Department of Natural Resources conducted a fish-netting survey. They quantified what fishermen like Bob Lambert had already noticed. Between 1996 and 2007 bluegill numbers dropped from 458 per net-day to 62, crappie from 340 to 26, and largemouth bass from 23 per mile of shocking to seven.
“When the good diversity and density of aquatic plants disappeared… so did the desirable fish species,” explained Tim Larson, retired DNR fisheries biologist who conducted the study. “A good fishery and aquatic plants coexist.”
By the Numbers
In the Park Lake Watershed
1,920 dairy cattle
1,612 beef cattle
5,780,245 gallons of manure annually
In 2009, Columbia County and the University of Wisconsin-Stevens Point began a two-year study to understand where the sediment and phosphorus was highest in the watershed. Sampling sites were established in streams in four locations above Park Lake and one downstream.
The study revealed that high levels of phosphorus routinely moved through the streams. All but one stream site showed median concentrations well above Wisconsin’s phosphorus criteria level for streams (75 parts per billion), and during 2010, samples from the three had double this value.
Until this recent study, many landowners wouldn’t accept the relationship between their land use and nearby water quality. Some still don’t.
Harold McElroy, a farmer in the watershed, was initially skeptical but he’s been persuaded by the evidence.
“I was surprised by how quickly sediment [in the stream] that was washed out by the flooding filled in again. Within a year, areas that had water depth of three to four feet were filled in, only to be six to eight inches deep,” said McElroy, now also a conservation technician with Columbia County.
Resource managers say changes in land use are the only way to address the lake’s phosphorus and sediment levels, but they acknowledge that landowners face financial challenges—concrete bunker-like storage facilities for manure that could make a difference are not cheap, and erosion-control efforts require technical expertise.
Everyone acknowledges there’s a lot of work ahead.
“Park Lake has great potential,” said Bruce J. Rashke, Park Lake Management District chair. “With community support, that potential can be realized in the form of clearer water and a better fishery while maintaining areas for other recreation. The challenge is finding the community energy to realize that potential.”
Nancy Turyk is a water resource scientist for the Center for Watershed Science and Education at the University of Wisconsin-Stevens Point. Chris Arnold is a water resource specialist for Columbia County and is working on his master’s degree with this project.
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