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Island Building in Pool 8, Upper Mississippi River


Wigwam Slough, Pool 8, Upper Mississippi River

Wigwam Slough, Pool 8, Upper Mississippi River

Goose Island: Wigwam Slough

La Crosse County, Wisconsin

Contradictory processes happen along the margins of Goose Island, a classic V-shaped island off the Wisconsin bank, south of LaCrosse. Running Slough, which flows out of a large complex of backwater sloughs and ponds, runs between Goose Island and the delta of Mormon Creek. Together, they form a mosaic of marshes and bottomland forests. The complex was silting in with sediment carried to the Mississippi from the Black, La Crosse, and Root Rivers, and Mormon Creek. On the riverside of Goose Island, Wigwam Slough runs between the island and the transitional backwaters in the mid-section of Pool 8, where wind fetch and wave wash eroded the islands.

Between 1989 and 1999 the Corps of Engineers and the Minnesota and Wisconsin Departments of Natural Resources through the Environmental Management Program reconstructed islands that had washed away, using dredge materials. The agencies completed the first two phases of stages 1 and 2 of the 5 stages of the project by 1999. In 2002 they completed design of stage 3, parts of which were scheduled for construction as soon as the work on Stage 2 is complete.

 Beginning in the summer of 2001, the Corps of Engineers drew down Pool 8 by eighteen inches to expose submerged sandbars and allow dormant seeds to germinate. The Flood of 2001 delayed start of the drawdown by three weeks and shortened its duration to forty days. It did, however, expose two thousand acres of sediment. The seeds responded: arrowhead, nutgrass, rice cutgrass, millet, smartweed, and American lotus. Fifty species of moisture-loving plants, emergent plants, and aquatic plants took root. Shore birds and wading birds patrolled the exposed mud flats. Swimmers basked on the sandy islands; campers pitched their tents; anglers cast their lines.

Plants in the mid-section of the pool remained above water longer than those in the lower regions of the pool, which were reinundated in mid-August. In October migrating waterfowl–tundra swans, ducks, and geese–stopped to rest and feed on the new plants.

U.S. Geological Survey personnel from the Upper Midwest Environmental Sciences Center at Onalaska, Wisconsin monitored the growth of the vegetation in eight backwater areas in Pool 8, including the pond between Goose Island and the delta of Mormon Creek. There they found an increase in both submergent plants–coontail and various pondweeds and rooted floating leaf plants–water lilies. The agencies repeated the drawdown in 2002.[i]

All this is good news because more and more ducks are depending on the Upper Mississippi Wildlife Refuge.  A half million birds migrated through the refuge in the fall of 2008, bypassing lakes in Minnesota and Wisconsin, which have become unsuitable for them. Their numbers have been growing for 10 years.

[i]             Eberhard, Christina, Drawdown, habitat restoration may be coming to Pool 5 soon,” Winona Post Online, Sunday, August 11, 2002; USGS, Upper Midwest Environmental Sciences Center, Vegetation Response to a Water-Level Drawdown of Pool 8 of the Upper Mississippi River,” http://www.umesc.usgs.gov/aquatic/drawdown_p8_veg.html; USGS, Upper Midwest Environmental Sciences Center, “ Pool 8 Transect Data Summary,”  http://www.umesc.usgs.gov/data_library/vegetation/transect/pool8/p8_summary.html; Verstegen, Peter, “Pool 8 drawdown recharges plants, helps waterfowl,” Crosscurrents, October, 2002, St. Paul District, U.S. Army Corps of Engineers, http://www.mvp.usace.army.mil/docs/crosscurrents/October2002a.pdf.

2 Responses

  1. My friend on Orkut shared this link and I’m not dissapointed at all that I came here.

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