Restoring Life-giving Water to Chiwaukee Prairie
A TNC restoration project will protect groundwater flows that are vital to people and the globally important wetlands at Chiwaukee Prairie.
From marsh marigolds and shooting stars in spring to gentians and blazingstar in late summer and fall, Chiwaukee Prairie State Natural Area is beautiful in all seasons. A restoration project The Nature Conservancy is launching in January 2019 will protect the life-giving water that is vital to the prairie’s survival.
Chiwaukee Prairie is a series of undulating sandy ridges and wet swales that developed as water levels in Lake Michigan dropped after the last glacier retreated from Wisconsin. This mix of wet and dry habitats is one of the reasons the prairie is home to more than 400 different wildflowers, grasses and other plants.
GROUNDWATER IS VITAL TO DIVERSITY
“A consistent flow of groundwater is a key ingredient to the diversity of life at Chiwaukee Prairie,” says Nick Miller, TNC science director in Wisconsin. “The water feeds the fens and wet prairies, providing the moisture and nutrients like calcium that enable rare plants like grass-of-Parnassus and lesser fringed gentian to survive.”
A 2004 Southeast Wisconsin Regional Planning Commission report alerted TNC to the fact that the land west of the State Natural Area serves as a critical groundwater replenishment area. When rain falls on the dry, sandy portions of the land, it infiltrates through the soil into the water table below and eventually flows east to the prairie. At some places in the prairie, this groundwater comes to the surface, bathing plants and walking shoes alike.
Proposed development of these higher, drier parts of the property into mixed use residential and commercial space would have threatened the supply of groundwater the prairie depends on. It would also have eliminated one of the largest expanses of plant and wildlife habitat remaining in this rapidly-urbanizing area along the coastal corridor between Milwaukee and Chicago.
“Groundwater modeling done by the U.S. Geological Survey predicts that development of the land west of Chiwaukee Prairie could have dropped groundwater levels in the fens and wet prairies by as much as several feet, threatening some exceptional wetlands and rare native plants,” Miller says.
LAND PROTECTION AND RESTORATION
Over the past 5 years, with support from our members, TNC has worked with local landowners to acquire 150 acres west of the State Natural Area. While the land contains a few acres of healthy wetland, many were damaged or destroyed when a network of drain tiles and ditches was constructed by previous landowners to move water off the property. Much of the land has also become overrun by invasive trees and brush.
Starting in January 2019, TNC launched a major restoration effort to remove the invasive trees and brush, restore wetlands and a more natural surface and groundwater flow, and replant the land to native prairie grasses and wildflowers.
“We plan to improve or restore about 75 acres of wetland habitat and another 75 acres of former prairie and oak savanna on the higher ground,” says Stephanie Judge, TNC land protection specialist who is leading the restoration effort. “Once the ground is frozen, we will start removing the invasive and undesirable trees and shrubs. Eventually we’ll fill the ditches and disable the drain tiles to restore the natural flow of groundwater from our lands east to the State Natural Area.”
THE FUTURE AT CHIWAUKEE PRAIRIE WEST
When restoration is complete, the land will offer substantial habitat for monarch butterflies and other pollinators through reestablishment of native prairie cover. It will feature a mix of grassy habitats and shallow wetlands, which will also provide habitat for shorebirds including greater yellow legs, sandpipers, plovers, dowagers and godwits.
The restoration will also stop the excessive flow of nutrient-laden storm water runoff from this site through its ditch and drain tile network. Instead, the changes we make will capture and keep more of the water on this property, allowing it to infiltrate into the ground, replenishing the supply of groundwater. This will increase the supply of clean drinking water for people and feed the springs that are vital to the health of the adjoining Chiwaukee Prairie State Natural Area.
“Chiwaukee Prairie West will also be a great place to take a walk or run, see a native prairie close up and look for birds and other wildlife,” says Judge.