Dane County plans to spend $10 million on land that will expand the Pheasant Branch Conservancy by 20 percent, bringing new recreational opportunities to the popular prairie reserve and divert more than 2.6 million gallons of water that would otherwise heighten Lake Mendota flooding concerns.
The 160-acre purchase is the most expensive conservation buy in county history.
"When we look at all of the efforts that we’ve undertaken in order to keep water where it lands to slow down the runoff of that water into the watershed so we can reduce flooding, this is the exact type of project that’s so important,” Dane County Executive Joe Parisi said as shafts of sunlight illuminated the black plowed earth surrounded by prairie on the Acker family farm, a dairy and grain operation in the town of Springfield, northeast of Lake Mendota.
The Acker family will grow one last crop before the county returns the entire farm to prairie, enhancing the land’s ability to retain and store water.
The conservation project will include wildlife areas, add to Pheasant Branch’s network of hiking trials and possibly be the site of a regional bike trail connector to Governor Nelson State Park.
But the main impetus of the purchase is flood control. Parisi recalled last summer’s Aug. 20 storm that pummeled parts of the county with 15 inches of rain in one day, raising concerns that Lake Mendota could breach its dam, with catastrophic results.
“We continue to experience rain events like we really haven’t before,” Parisi said. “With flooding last year, this area was certainly hit hard.”
The restoration of the land is also projected to slow algae growth by reducing phosphorus runoff by more than 550 pounds a year. One pound of phosphorus can produce up to 500 pounds of algae.
The purchase works in concert with other efforts to avoid a replay of last year’s weeks-long flooding event and subsequent rains, which prompted an exhaustive sandbagging campaign in low-lying areas on the isthmus.
Parisi said the county is working with state agencies to open up four key areas that have become clogged with sediment between the four lakes in the Yahara chain that had stifled water flow and prevented the lakes from returning to normal levels.
"The challenge we had last year is we couldn’t move water through and out of the system fast enough,” Parisi said.
Part of the restoration effort will be taken on by the Friends of Pheasant Branch Conservancy, which has been working for 25 years to restore the 550-acre conservancy to prairie. The conservancy is owned by the county, the state Department of Natural Resources and the city of Middleton.
Lloyd Eagan, co-president of the group, said the roots of the plants that will cover the farm field will be key to its ability to retain runoff and improve water quality.
“Prairie plants have very, very deep roots,” she said. “So when you transfer a property to a prairie you greatly increase the amount of water that will infiltrate. So it’s not just where it lands, it’s actually recharging the groundwater.”