View of the Refuge from Buena Vista EC #3
In Wisconsin, United States
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This is one of a series of EarthCaches along the Upper Mississippi River.
Enjoy learning about these wild places on the Upper Mississippi River National Wildlife and Fish Refuge. This area is open 24 hours a day and 365 days a year.
Post a picture of yourself holding your GPS with the Lock and Dam seen on this stretch of the Upper Mississippi River National Wildlife and Fish Refuge. Send your answers to the profile email:
What geological process occurred above the Lock and dam that removed all the islands?
What river features do you see downstream of the Lock and Dam?
A Natural River
Prior to 1866, the Upper Mississippi River was a mosaic of channels, sand bars and wooded islands. In spring, the river flowed fast and furious, scouring new channels and forming sandbars in unexpected places. In summer, it was so shallow in places that a person could walk across it. But the natural river was too dangerous and unreliable for commercial boat traffic, so, in 1866, the 4-foot channel project was begun. It was the first of several channel improvement projects that would eventually result in the building of the locks and dams in the 1930s to maintain a 9-foot shipping channel. When the system of locks and dams was completed, the free flowing river had been transformed into a series of navigation pools. The locks and dams maintained high and relatively stable water levels in the lower portion of the pools, which ensured the passage of tows and barges even in the middle of summer.
Pools on the River
Each lock and dam creates a pool upstream of it. So at lock and dam 5 the stretch of river above at lock and dam 5 is called Pool 5. There are 29 locks on the Upper Mississippi maintained by the U.S. Army Corps of Engineers. There are some quirks in the numbering of the dams. There is Lock and Dam 5 and a Lock and Dam 5A and there is no Lock and Dam 23.
Changes in River Habitat
For several decades, these pools supported a wealth of fish, wildlife and aquatic habitat, but it gradually diminished. The high water levels, caused by the locks and dams, made the islands in the lower portion of the pools more vulnerable to erosion from waves, and many of them disappeared. In addition, material carried by the river and soil washed from the nearby eroding islands gradually filled in channels and deep holes. Aquatic plants that grew in the shallow water bordering the islands were affected by these changes, and many formerly lush plant beds either decreased in size or disappeared completely. These plants are part of the foundation for the web of life in the river providing food and shelter for fish and wildlife. Some pools were affected more than others by this chain of events, but many of the pools now have a wide open expanse of shallow water above the lock and dam. These areas are much less productive for fish and wildlife. Areas below locks and dams can be reflective of what it might have looked like prior to dam construction. These areas may have braided streams, running sloughs, islands and channels.
The Mississippi River is world renowned as a migration corridor for waterfowl. Aquatic vegetation provides seeds and tubers, as well as habitat, for an abundance of invertebrates, all of which are a critical food source for migrating waterfowl. Weekly aerial waterfowl surveys have been conducted during the fall by the U.S. Fish and Wildlife Service to estimate total use days (1 use day = 1 waterfowl for 1 day) for puddle ducks (such as mallards and wigeon), diving ducks (such as canvasbacks and scaup), geese, and tundra swans in Upper Mississippi River Pools 4 through 13. Puddle ducks feed primarily in backwater areas on plant seeds, insects, and other items. Flooded annual plants like smartweed are especially attractive.
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Last Updated: on 6/20/2015 2:44:56 PM Pacific Daylight Time (9:44 PM GMT)
Coordinates are in the WGS84 datum