Upper Midwest Environmental Sciences Center

Figure 1.

Long Term Resource Monitoring Program study reaches for macroinvertebrate sampling.

• Pool 4
• Pool 8
• Pool 13

• Pool 26
• Open River Reach
• La Grange Pool

Navigation Pool 4 is 73 km (44 river miles) long and includes 14,700 ha (36,300 acres) of aquatic habitat. It is located between Lock and Dam 3 (above Red Wing, Minnesota) and Lock and Dam 4 (Alma, Wisconsin). Major tributaries include the Cannon and Vermillion Rivers on the Minnesota side and the much larger Chippewa River on the Wisconsin side. Lake Pepin, a riverine lake created by the Chippewa River delta, is located in the middle of Pool 4. The location of Lake Pepin divides the rest of the pool into upper Pool 4 and lower Pool 4. The smaller backwaters of upper Pool 4 have been degraded by sedimentation, whereas the larger backwaters of lower Pool 4 provides much better habitat for vegetation.

Navigation Pool 8 is 39 km (23 river miles) long and is bounded by Lock and Dam 7 (Dresbach, Minnesota) to the north and Lock and Dam 8 (Genoa, Wisconsin) to the south. It encompasses 9,000 ha (22,100 acres) of aquatic habitat. Major tributaries include the Black, Root, and La Crosse Rivers. The upper section of Pool 8 has high bank islands adjacent to the main channel, deep secondary channels, and backwater sloughs. The middle section contains low islands, braided channels, and small backwater sloughs. The lower section is a large open expanse of water.

Navigation Pool 13 is 52 km (34 river miles) in length and is bounded by Lock and Dam 12 (Bellevue, Iowa) to the north and Lock and Dam 13 (Fulton, Illinois) to the south. It encompasses 11,400 ha (28,100 acres) of aquatic habitat. Similar to pools upstream, Pool 13 contains many high bank islands adjacent to the main channel in the upper section, braided backwater channels and sloughs in the middle section, and a large open lake-like area in the lower section of the pool. Major tributaries include the Apple and Plum Rivers on the Illinois side and Maquoketa and Elk Rivers on the Iowa side.

The Navigation Pool 26 study area includes water bodies along the Upper Mississippi River from Lock and Dam 25 (Winfield, Missouri) to Lock and Dam 26 (Alton, Illinois)–63 km (39 river miles) long–and the lower Illinois River from its confluence with the Mississippi River north to Illinois River mile 12. This reach of the two rivers is bordered by high bluffs on the Illinois side and low elevation floodplain on the Missouri side. The reach encompasses 9,500 ha (23,700 acres) of aquatic habitat. Presently, most of the backwaters of the lower Illinois River are isolated from the river by low levees so as to decrease sedimentation and allow management for waterfowl. Likewise, many of the secondary channels of the Mississippi River are isolated from the river on the upstream side to create backwaters and to reduce sedimentation.

The Open River Reach study area in the open river is 84 km (51 river miles, from river mile 29 to 80) long. The study reach has approximately 7,241 ha (17,893 acres) of aquatic habitat in the form of open water, sand and mud flats, and swamps and marsh. The floodplain is extensively disconnected from the mainstem river by levees. Many of the islands are now joined to the mainland and most side channels contain closing structures and become disconnected from the mainstem at moderately low flows. This river reach is characterized by turbid water, high water velocities, and sand substrate; thus, the aquatic communities are dominated by more obligate riverine species than the pooled portion of the Upper Mississippi River. Major tributaries to the Open River study area are the Little River Diversion Channel in Missouri, and the Big Muddy Rivers and Cache River Diversion Channel in Illinois.

La Grange Pool on the Illinois River is about 130 km (80 river miles) long and encompasses 10,750 ha (26,500 acres) of aquatic habitat. It is bounded by Peoria Lock and Dam to the north and La Grange Lock and Dam to the south. This reach has the highest proportion of backwaters, except for Pool 4, but these backwaters are highly degraded by excessive sedimentation over the last 150 years. Many backwaters are isolated by low levees to enhance waterfowl habitat management. Major tributaries include the Sangmon, Mackinaw, and LaMoine Rivers.