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Duffy's Marsh Wetland Restoration

Aerial Photo of Duffy's Marsh in Marquette County, Wisconsin. [NRCS Photo]

Duffy’s Marsh is a 1,732 acre wetland restoration project in Marquette County, Wisconsin. 

It is the largest wetland restoration in the state, and one of the largest in the nation, covering about 1,000 acres of open water area and 700 acres of grassy wetland and upland. Nine neighboring landowners have worked together with the USDA Natural Resources Conservation Service (NRCS) to restore this marsh to its former beauty and wetland value. The land remains privately owned, with permanent easements to protect it in the future.

Through the Wetlands Reserve Program, private landowners can restore and preserve wetlands that have been previously drained for agricultural land. NRCS purchases a conservation easement and reimburses the cost of construction and seeding to make it affordable for the landowner to retire the wetland from crop production.

Construction began in late July, and was completed in one month. The restoration work consists primarily of plugging the network of ditches that drained these former mint, carrot, onion and corn farms. Embankments and ditch plugs are constructed entirely native soils, which are a mucky peat organic type of soil. The marsh was restored with only 13 ditch plugs. A single rock spillway provides an outlet for the water.

The marsh has the capacity to normally hold 55 million cubic feet of water. When full, water from the marsh will flow out the rock outlet on the north, to the Grand River, to the Fox River, to Green Bay, and into Lake Michigan.

The 3,000 feet of newly constructed dikes connect to remnant spoil piles from old ditching to create a nearly continuous walkable embankment for four miles around the marsh.

Value as Wildlife Habitat

The marsh will provide open water, grassy wetlands and uplands will provide habitat for waterfowl (ducks, geese, swans), wading birds (herons, egrets) and shorebirds such as yellowlegs. It is located within 60 miles of the Horicon National Wildlife Refuge on the flyway for a wide variety of migratory birds.

Flood Reduction 

Duffy’s Marsh will have the capacity to normally hold 55 million cubic feet of water, significantly reducing the risk of flooding and flood damages downstream. NRCS designed the embankments to contain runoff from storms that drop up to 4 inches of rain in 24 hours (a 10 year storm).

Size and Location:

With over 1,700 acres or almost 3 sq. miles., Duffy’s Marsh is the largest Wetlands Reserve project in Wisconsin. It is located in the Grand River Watershed which feeds into the Great Lakes Basin.


The organic soils of Duffy’s Marsh are much like the potting soil available in stores. In their natural state , these mucky peat SOILS have a low fertility and high water-holding capacity. Water and air can move freely through these soils. If water levels are controlled, they can be successfully used for agriculture. Their best use is, naturally, as wetland.

 The mucky-peat soils of Duffy’s Marsh owe their origin to two major geologic events. The glacier ice, advancing across east central Wisconsin, gouged out its original basin. Water from the melting glaciers formed a lake basin. This lake basin was sandy along its beach areas, but the deep water areas had fine water-sorted deposits.

As the climate warmed, vegetation started to encroach upon the water areas. Over the last 10,000 years, sedges and marsh grasses slowly replaced the water areas. The wet environment of the marsh inhibits the decomposition of these plant remains, so it accumulates. The organic soils we see today are simply centuries of decayed plant residues. Each winter, we add another layer of dead plants. Research on bogs in Wisconsin shows that these organic soils form at a rate of one inch every 40 years. Duffy’s Marsh has an organic layer up to 3’-9’ thick. 



In 1918, a local landowner named L.J. Dartt, noticed an old Indian campsite near here and reported it to Samuel Barrett, an archaeologist cataloging sites around Buffalo Lake. Mr. Dartt felt that the site was used only in winter because the ground was too wet at any other time of year. In 1993, archaeologists revisited the site when planning the Duffy’s Marsh restoration. Because the only access to the site was through standing water, the site was re-named the "Dartt Wader" Site (though certainly in this post Star Wars Era, the play on the name of the most dastardly and evil Enemy of the Universe was not ignored).

Artifacts from the Dartt Wader Site suggest use by the Middle Woodland Hopewellian people from 100 AD to 300 AD. Although the primary sphere of Hopewellian influence was in the Ohio River Valley hundreds of miles to the south, they spread their influence through the development of a sophisticated trade network that ranged from Montana to Florida and New York. What did they want from Duffy’s Marsh? The Hopewellians may have camped at the marsh on journeys from the copper deposits in the north to home villages farther south, or it may have been permanently occupied.

Image of Snyder's PointA Snyder’s point similar to this was found at the Dartt Wader Site. Snyder’s points are diagnostic of the early Middle Woodland period and appear with the rise of Hopewellian influence.

Find out more about the Wetland Reserve Program at your local NRCS office.