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Featured
Activity - November, 2001
MISSISSIPPI RIVER
MANAGEMENT
- A String of Pearls
-
by
Mike Giffin
Iowa sits between the Mississippi and Missouri
rivers but on paper is placed in the Mississippi Flyway as most migratory
birds that are raised in Iowa head southeast and migrate along the Mississippi
river. The Mississippi River provides a corridor stretching North
to South from near Canada to the Gulf of Mexico. The river along
Iowa’s border is comprised of many beautiful backwater lakes, marshes,
sloughs, islands and open impounded pools. Birds migrating in the
fall and spring use this corridor. Many species of birds use this
habitat including small song birds, hawks and falcons, herons and egrets,
and of course waterfowl.
Management of the river corridor is complex.
In 1930, Congress authorized the Nine-foot Navigation Project and charged
the Army Corps of Engineers with ensuring that barge traffic on the Upper
Mississippi River would have a nine-foot channel for shipping. The
Corps proposed placing 26 Locks and Dams on the Upper Mississippi River.
These dams impound water during periods of low flow to create pools that
insure that the main shipping channel of the river is at least nine-foot
deep. This project was completed in the early 1940’s.
The pools created by the locks and dams filled
with water submerging islands, flooding fields, wet meadows and creating
many backwater lakes and marshes. These newly formed marshes and
backwater areas then began to do what lakes and marshes do; provide habitat
for fish and wildlife and trap sediments. Now many of these areas
have filled in to the point where their value to wildlife and fish is diminished.
The Nine-foot Channel Project increased the
amount of water in the lower sections of the pools. These deeper
water areas changed the vegetation to submergent aquatic plants such as
wild celery, sago pondweed, and in addition produced large numbers of fingernail
clams, all great food sources for diving ducks. This was good news
for the migrating waterfowl that need these valuable food sources during
migration. Almost two thirds of the continental population of canvasbacks
stop, feed and stage on pool 9 of the Upper Mississippi River every year,
and Tundra swans congregate in the rich arrowhead stands of pool 8 as they
migrate east to the Chesapeake Bay.
Not only did diving ducks benefit from the pooling of the Mississippi,
but so did dabbling ducks, as the middle sections of the pools created
many marshes where lotus and Sagitaria (arrowhead or duck potato) thrived.
These moist soil areas dry out after the spring flood, become mudflats
and germinate with moist soil plants. The river under natural water
hydrology (without the nine foot navigation project) would flood many areas
in the spring but then go to a very low flow condition in the summer. Then
as the fall rains came, the river would rise a couple of feet and create
a valuable food resource at a time that coincided with the fall waterfowl
migration.
The Current Problem
Historically, the fall rise would flood many acres
of former mudflats that had seeded to moist soil plants like smartweed,
beggertick, and wild millet; however, under current Lock and Dam regulations,
to maintain the nine-foot channel, the river never goes to a low stage
in the summer. The marshes and backwater lakes are filling in with
sediment and not providing the good high quality food resources for migrating
waterfowl in the fall as they did in the past.
Habitat Rehabilitation and Enhancement Projects.
The Iowa DNR as a partner in the Upper Mississippi
River Environmental Management Program proposes projects that will help
rehabilitate the Upper Mississippi River system for fish and wildlife habitat.
These projects include: dredging backwater lakes and marshes, constructing
water control structures to provide the ability to manage water levels
independent of the nine-foot navigation project, and creating islands to
protect areas from wind driven waves and provide loafing and nesting areas
for water birds. Water control is key to providing quality
habitat along the river and it is important that habitat be provided all
along the river corridor.
The most ambitious work currently under way,
is investigating modifying how the Corps manages water levels. The
Iowa DNR and the other states along the corridor are studying where, and
under what water regime, pools can be drawn down to establish preferred
vegetation, while maintaining the nine-foot navigation channel. To
date experimental drawdowns have been tried in pool 26, 13 and 8.
Research indicates that a one-foot drawdown in pool 13 near Clinton Iowa
would expose 443 acres of aquatic area that has not been exposed since
the late 1930’s. These acres would initially provide mudflat habitat
beneficial to shorebirds, before being taken over by emergent vegetation,
which, when flooded, would provide marsh vegetation benefiting both fish
and waterfowl. Also submergent vegetation would increase in deeper
areas of the pool as a result of a drawdown because light would penetrate
to the bottom of the water column and stimulate plant growth.
Ideally the Corps would annually manage each pool to provide
wildlife habitat, but realistically politics, weather and other variables
cannot guarantee that ideal habitat conditions will be available each year.
As an alternative, the Iowa DNR has adopted a long-range plan to provide
a series of habitat areas along the Mississippi River. Biologists
have learned that high quality food sources need to be present about every
50 to 70 miles along the migration route to maintain the body condition
of migrating waterfowl. To provide this food resource, the Iowa DNR
Wildlife section is working to provide management areas with water control
capabilities every 50 miles along the Mississippi River. Currently
three areas owned by the DNR along the river allow such water control,
Green Island, Princeton, and Odessa, and the DNR is working to improve
water control abilities at two other DNR areas at Poole Slough (near New
Albin) and Blackhawk bottoms (near Burlington). In addition and in
partnership with the Fish and Wildlife Service additional water control
has been proposed for Guttenberg waterfowl ponds (near Guttenberg), John
Deere Marsh (above Dubuque), and Pleasant Creek (below Bellevue).
For additional information regarding
the Iowa DNR and Mississippi River management individuals can contact Mike
Griffin, the Mississippi River biologist at (319) 872-5700.
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Last Update November
2001
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