Upper Miss Refuge at Spring Lake EC #41
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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
Requirements for logging the cache:
1. Upload a picture of you and GPSr and Spring Lake.
2. Email through our profile, the answer to the following question, do not post it on the cache page: When you stand at this overlook which river zone is represented? (braided stream, central or open water) Read the information, look at a river pool map and visit the site and you’ll be able to answer the question.
The original Spring Lake was a spring fed lake of about 20 acres with an average depth of 4-5 feet. After World War I, local farmers diked and ditched the area to plant crops, primarily corn and wild hay. Some islands still show remnants of the buildings and farmsteads constructed in the past. Spring Lake was destined to be inundated by the construction of Lock and Dam 13 so it was purchased by the federal government and Spring Lake was no longer farmed.
Seepage and springs gradually filled the area and by 1946, a 3,500 acre lake had formed within the diked area. Black bullhead populations provided excellent fishing opportunities until the flood of 1951 which broke the west dike followed by a flood in 1952 that broke the south dike. The breaks were repaired. The historic flood of 1965 broke the west dike and south dike was intentionally breeched to reduce water levels. The south break remains today.
After the dike broke, Spring Lake fluctuated with river levels which severely impeded the growth of aquatic plants that provided food and cover for fish and food for migratory waterfowl. Fish populations changed dramatically from bullhead to carp, buffalo, perch and channel catfish. The cost to repair and maintain the entire outer dike was prohibitive so a crossdike was constructed in 1968 to regain water level control on the upper portion of the area. Another historic flood in 1993 caused significant dike damage again. This flood, combined with the large amount of sedimentation occurring before and after, filled the lake to an averaged depth of less than 2 feet. In 1996, the Environmental Management Program provided $6M to rehabilitate the Spring Lake dike system.
As part of the Upper Mississippi River National Wildlife and Fish Refuge, Spring Lake is managed for wetland dependent wildlife and fish. It is an important rest stop for tens of thousands of waterfowl.
Lower Spring Lake contains 3,000 acres of backwater lake habitat which is connected to the Mississippi River but is protected from direct river flows by a dike on the west side. This diversion dike keeps heavy silt loads from directly flowing into and being deposited in Lower Spring Lake. The south end of the dike is open so that water backs into the area and water levels are equal to river levels. This helps to prevent breaching of the dike. Two water control structures in the dike allow control of water flows directly from the river in winter to increase oxygen levels for fish survival during periods of ice and snow buildup.
Upper Spring Lake contains 500 acres within 3 moist soil impoundments that are isolated from the Mississippi River by dikes. The water levels in the impoundments are intensively managed to produce natural plants that are high quality foods for waterfowl. Management of water levels also improves habitat for shorebirds, wading birds and other wetland dependent wildlife. During winter, the 3 interior water control structures and pump station are opened to allow fish passage.
The construction of Locks and Dams reshaped the character of the Upper Mississippi River National Wildlife and Fish Refuge habitats. Behind each dam is a navigation pool with three distinct zones. The braided stream zone is found in the upper portion of each pool, where narrow cuts and channels snake between islands of floodplain forests. This zone resembles the area prior to lock and dam construction. Here you might see wood ducks, woodpeckers or an elusive river otter. The central zone in the middle of each pool is where shallow water lies over old hay meadows and the stumps of trees cut before impoundment. This zone supports the best marsh development and is the haunt of dabbling ducks, muskrats, bass and panfish. The open water zone just upstream of each lock and dam, is the deep, open water where canvasbacks and other dividing ducks can be found.
Geological Features:
The Refuge lies within the Mississippi River floodplain, an ancient river valley filled with alluvial material (mud, sand, and gravel) carried and deposited by surface water. The river and its tributaries traverse sedimentary rock formations (dolomite, sandstone, and shale) that accumulated under inland seas during the early Paleozoic Era about 400
to 600 million years ago (Fremling and Claflin,1984).
In more recent geologic times, the river valley has taken shape due to the presence (and absence) of glacial action. Global warming ended the last period of glaciation, about 12,000 years ago, and melted glaciers created huge clear-water lakes. Glacial Lake Agassiz covered much of northern Minnesota, the Dakotas, and central Canada. Most of that lake emptied to the south via the River Warren through which water ran in torrents for about 3000 years, trenching the Mississippi River valley by as much as 200 feet (Fremling and Claflin, 1984). Once the flow from glacial lakes subsided, the river lost
much of its velocity and sediment transport capabilities. Sediment deposition ensued, and the valley partially refilled with sand and gravel. Several episodes of flushing and filling of the river valley have followed. Sand terraces that presently flank the river valley are remnants of ancestral floodplains not scoured during the most recent postglacial
floods.
Today, over 30,700 miles of streams course through the basin, merge, and eventually enter the Upper Mississippi River Basin (Figure 3). That number does not include many smaller streams not detected by large-scale mapping techniques (Gowda, 1999). The Refuge receives water from 530 of the estimated 1300 streams that occur within the
Upper Mississippi River Basin. The illustration of sub-basins by stream order helps depict the relative size of drainage areas and channel lengths. The ordering system (Strahler, 1957) starts with the uppermost channels in a drainage network, they are
the first-order streams downstream to their first confluence. A second-order stream is formed below the confluence of two first-order channels. Third order streams are created when two second-order channels join, and so on. “Tributaries of the Mississippi
have steeper gradients than the master stream and they now deliver sediments faster than the Mississippi can remove them; thus the valley floor is slowly agrading once more” (Fremling and Claflin,1984).
Much of the Refuge follows the Mississippi River as it flows through the carved Driftless Area, a nonglaciated “island” within a huge area of central North America shaped by a series of glaciers (Albert, 1995). This region has minimal amounts of glacial deposits known as “drift” and is therefore known as the Driftless Area. This landscape features
a combination of steep, exposed bluffs and eroded ravines that bound the wide floodplain of the Upper Mississippi River, creating an unmatched wild and scenic character so prized by many viewers.
The blufftops mark the edge of a plateau, extending many miles from the river, that is capped with loess soils that range in depth from 2 to 20 feet, the thinnest being along the valley walls. The Driftless Area includes parts of southwest Wisconsin, southeast Minnesota, northeast Iowa, and northwest Illinois. It also is called the Blufflands or Paleozoic Plateau.
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