Limnological monitoring on the UMRS, 1993 1996: LTRMP Pool 26 Field Station

Soballe, D. M., E. Ratcliff, B. Kerans, and T. Mihuc. 2002. Limnological monitoring on
the Upper Mississippi River System, 1993 1996: Long Term Resource Monitoring
Program Pool 26 Field Station. U.S. Geological Survey, Upper Midwest Environmental
Sciences Center, La Crosse, Wisconsin, October 2002. LTRMP 2002-P002. 18 pp. +
Appendixes A-F (NTIS# PB2003-101577)

ABSTRACT

Since 1988, the Long Term Resource Monitoring Program (LTRMP) staff have
performed basic limnological field measurements in the Upper Mississippi River System.
The period of this report (1993 96) includes a major revision of the LTRMP sampling
design in 1993 that added randomization, broader spatial coverage, and increased
monitoring of tributaries and locations that allow monitoring of material transport. The
1993 96 water quality data for the Pool 26 area show long-term declines in the
concentrations of total nitrogen, nitrate nitrite nitrogen, and soluble reactive phosphorus
after the large flood in 1993. The data also indicate that contiguous backwaters have
unique water quality among the sampling strata, characterized by higher turbidity, volatile
suspended solids, and fluorometric chlorophyll a, and lower total nitrogen and
nitrate nitrite nitrogen. 

The Missouri and Illinois Rivers significantly alter the Mississippi River main stem in the
Pool 26 study area. The Missouri River contributes high turbidity, silicate silica, and total
suspended solids, whereas the Illinois River contributes elevated concentrations of total
nitrogen, nitrate, total phosphorus, and soluble reactive phosphorus. Dissolved oxygen
concentrations (>5 mg/L) were good in the Mississippi River main stem but were
somewhat lower in the Missouri and Illinois Rivers. In the Illinois River, concentrations
fell to or below the Illinois general use water quality standard of 5 mg/L every summer
during 1993 96.

KEYWORDS

Annual report, limnology, LTRMP, Mississippi River, water quality