The duck are migrating and need to find quiet places to fatten up and rest about every fifty miles. There are refuges on the mainland, like Green Island in Iowa and Spring Lake in Illinois. And there is the river itself, once a maze of islands and sloughs, changed by the construction of the dams:
“From Minneapolis to Alton, the river drops 327 feet in elevation. Along that stretch of the Upper Mississippi, the locks and dams and the nine-foot channel formed a river staircase of twenty-six shallow lakes or pools. The locks lifted or dropped shipping from one pool to the next. The dams created three distinct habitats within each pool: In the tailwater, downstream from the dam, the river remained almost unchanged, a maze of deep sloughs and wooded islands, a home to diving ducks, especially scaup. Here, transitory islands that might have washed away in the next flood became permanent islands. In the mid-section of each pool, there were large areas of shallow, open water where the dams flooded hay meadows and floodplain forests. These areas turned into broad marshlands–Weaver Bottoms, Spring Lake, and others, where wildlife–fish and puddle-ducks like mallards–thrived.”–From The Mississippi: A Visual Biography
At the end of the twentieth century the Wisconsin DNR and the Corps of Engineers made the first attempts to aleviate the flooded conditions of the lower third of the navigation, by drawing down water levels behind the dams. They started on a small scale in the 1990s and graduated to whole pools in the first years of the twenty-first century, when they drew down Pool 8 and watched the grasses grow.
At the beginning of 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]
[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.