Mequon Nature Preserve: Constructed Wetlands
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An EarthCache adventure is treasure hunting for the caches that the Earth has stored. EarthCache sites do not use stored containers; their treasure is the lessons people learn about our planet when they visit the site. Visitors to EarthCache sites can see how our planet has been shaped by geological processes, how we manage the resources and how scientists gather evidence to learn about the Earth.
The Streich Family Wetlands is a complex of wetlands around the PieperPower Education Center on the Mequon Nature Preserve that includes artesian springs, ephemeral and man-made ponds, a watershed divide and Trinity Creek. The subject of this EarthCache, however, will be the concept of man-made or constructed wetlands.
WHAT GOOD ARE WETLANDS?
Wetlands have been misunderstood, destroyed and polluted for generations, and yet wetlands make very important contributions to the surrounding natural and human communities. They absorb rainwater and spread excess water out so it can slow down, soak in, and reduce flooding and erosion. They help purify water by filtering out sediments. They also help to replenish ground water.
The function of most natural wetland systems is not to manage to wastewater, however, their high potential for the filtering and the treatment of pollutants has been recognized by environmental engineers that specialize in the area of wastewater treatment. Constructed artificial wetland systems are highly-controlled environments that intend to mimic the occurrences of soil, flora, and microorganisms in natural wetlands to aid in treating wastewater effluent.
MAN-MADE PONDS
Tile drainage is an agriculture practice that removes excess water from soil subsurface. By adding drain tile, the water table is effectively lowered, and plants can properly develop their roots. The lack of water saturation allows oxygen to exist in the soil around the roots. Drain tile prevents the roots from being under the water table during wet periods that could cause excessive plant stress. By removing excessive water, crops use water they have more effectively. An increase in crop yield can be simply summarized by the following: Simply by forcing the plants to have more developed roots, the plants can more effectively absorb more nutrients and water.
Ecologically, however, the expansion of drainage systems has had tremendous negative effects. Hundreds of thousands of wetland species experienced significant population declines as their habitat was increasingly fragmented and destroyed. Further, in bypassing the natural flow of water from the surface to the water table, drainage systems often prevent the natural filtration of water provided by soils and wetlands.
Agricultural drain tiles were removed from the area east of the Education Center by the Wisconsin Waterfowl Association in 2007 and the first ponds were excavated. Twenty-four hours after the ponds were excavated, artesian springs filled the ponds with water. Within days, quick-growing grass seed was broadcast over the ground to stabilize the bare soil and prevent erosion. In the weeks and months that followed, volunteers planted thousands of native wildflowers and pounds of grass seed.
The ponds were divided by partial rock dams that provide habitat and force the water to meander and slow down. After a rainstorm, water running off the parking lots and the surrounding land joins water from the Trinity Creek and flows into the series of ponds. There the water is filtered and cleaned. Any silt or undesirable material carried by the water settles to the bottoms of the ponds before the creek continues on its path. In 2009, two more ponds were excavated between County Line Road and the parking lot at the Education Center. They are not spring-fed, but ground water and precipitation have filled them.
DE-CHANNELIZING TRINITY CREEK
Like many creeks and rivers in agricultural, suburban and urban settings, the Trinity Creek was channelized in this area – its bed was dug out and deepened. Waterways that are channelized are often straightened at the same time. In urban areas, the new stream or riverbed may be lined with concrete, so the water is confined to a straight, man-made path. Why? Channelization was done for flood control, because water can flow faster in a straight, deep trench than when the stream is winding across the landscape. When the path of the water is regulated, the land nearby can be reclaimed for farming.
But, channelization also has some significant downsides. It wipes out the wetlands along the shorelines of rivers and streams, so all of the “pluses” of wetlands are lost. The zones of shallow water along unchannelized rivers are important habitat, populated by emergent plants and by a huge number of animals including spawning fish. The faster-flowing water can also increase erosion, and the flooding that is avoided in one spot may happen farther downstream. The Milwaukee Metropolitan Sewerage District has spent millions of dollars to remove concrete channels and return streams to a more natural condition. De-channelizing the Trinity Creek is part of the recovery plan for the Mequon Nature Preserve.
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QUESTIONS: From the educational signs, fill in the blanks and email your answers to the Cache Owner (NOT in your "Found It" log).
About _____ of the world’s fresh water is found in the ground.
Some water that soaks into the ground enters a saturated zone called the _____.
When it is stopped by a _____ that it can’t get through, water seeks a sideways path, eventually reappearing at the surface as a _____.
Underground water that is trapped under a _____ may escape to the surface under pressure, forming an _____.
Creeks confined to straight channels flow _____ and cause more _____ than creeks that curve across the countryside.
As the creek passes through the pond system, its current _____ and dirt carried in the water _____.
This cleaner water leaves the ponds as _____ and continues on its path to _____ and then on to _____.
How many artesian springs feed these wetlands?
As this is a constructed wetland, there was a choice of where to locate it on the Nature Preserve property. Looking at the lay of the land, explain why this area might have been chosen. Your explanation should include a discussion of the change in elevation across the property, the direction of water flow and use of the term “water table” in it. You get a feel-good bonus if you can also determine which direction the watershed divide is located.
OPTIONAL: Although not required, your photographs of the Nature Preserve are welcome in your "Found It" log.
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My THANKS go out to the following people for their approval and guidance in setting up this EarthCache at the Mequon Nature Preserve:
Kristin Gies (Director), Jason Nickels (Education and Restoration Manager), Christine Nuernberg (Secretary/Treasurer, Board of Directors), Kate Redmond (Teacher-Naturalist author of the Mequon Nature Preserve Field Guide)
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