A suspended sediment budget for Pool 13 and La Grange Pool of the UMRS

Gaugush, R. F. 2004. A suspended sediment budget for Pool 13 and La Grange Pool of
the Upper Mississippi River System. Final report to U.S. Army Corps of Engineers. U.S.
Geological Survey, Upper Midwest Environmental Sciences Center, La Crosse,
Wisconsin. September 2004. LTRMP 2004-T004. 13 pp. + Appendixes A D.


ABSTRACT

The suspended sediment budget for Pool 13 of the Mississippi River and La Grange Pool
of the Illinois River was examined over a 3-yr period (October 1995 through September
1997). Pool 13 output was between 3.07 and 3.64 million t (metric tons) of suspended
sediment annually during the study period. Loads to Pool 13 were dominated by those
delivered by the Mississippi River (76%, 74%, and 66% in the 1995, 1996, and 1997
water years, respectively). Pool 13 exhibited sediment export (output greater than input)
in 1995, a balance in 1996, and marked sediment trapping (output less than input) in 1997.
Within the three study years, Pool 13 received its highest water and sediment loads during
spring (March through May) and this period was marked by sediment export. Suspended
sediment loads were trapped during the remainder of the year. La Grange Pool output was
between 3.71 and 5.04 million t of suspended sediment annually during the 1995 97
water years. The Illinois River accounted for less than 50% of the suspended sediment
load to the pool (19%, 25%, and 45% in the 1995, 1996, and 1997 water years,
respectively. La Grange Pool exhibited considerable sediment trapping in 1995 whereas
the 1996 and 1997 water years were much closer to a balance wherein output was within
5% of input. Generally, La Grange Pool received its largest water and sediment loads
during the late spring early summer period (April through June), but in 1997 the late
winter loads predominated. In all years, La Grange Pool trapped the sediments during
these high discharge, high loading periods and exported suspended sediments for the
remainder of the year. The distinct differences in the manner in which these pools process
suspended sediment loads may be related to the considerable differences between the
morphometry of these pools.

KEYWORDS

La Grange, Mississippi River, Pool 13, river, sediment budget, sediment load