A summary of water quality characteristics at selected habitat sites in Navigation Pool 8 of the Mississippi River for 1 January-30 December 1989

Five habitats were required to be sampled under the LTRMP: 
Channel Border Unstructured (CB-U), Channel Border - Wing Dam
(CB-W), Backwater Contiguous (BW-C), Backwater Isolated (BW-I),
and Impoundment (IMP).  Similar weekly trends were seen in all
five habitats during the year.  Water clarity as indicated by
nephelometric turbidity and Secchi disk depth transparency
decreased from winter to summer, then increased during late summer
and autumn. Dissolved oxygen (DO) showed similar trends in all
habitats, as did temperature.  A period of severe thunderstorms
during the end of May produced sufficient runoff to increase flows
in the river.  All habitats experienced a very noticeable decrease
in DO levels and a slight increase in average weekly turbidity and
velocity values at that time.  Data collected during comparable
temporal periods in 1988 and 1989 showed similar trends in all
habitats.  Some differences in measurements during the same
periods appeared to be a result of the severe drought conditions
experienced during 1988.  Average velocities were slightly greater
in four habitats during 1989 than during 1988, probably a direct
result of lower flows through the system.  Conductivity was
slightly greater in 1988 for all habitats, indicating a greater
concentrating effect due to low flows and higher average
temperatures during the summer.  Contiguous backwaters commonly
showed the greatest weekly range in DO, temperature, velocity,
specific conductance, and Secchi disk transparency.  This
variability coincides with the diversity found in the physical and
biological characteristics of Pool 8 contiguous backwater
habitats.