Water Resources Investigations Report 95-4021
Water Resources Investigations Report 95-4021
Data on water velocity, temperature, specific conductance, pH, dissolved oxygen concentration, chlorophyll concentration, suspended sediment concentration, fecal-coliform counts, and the percentage of suspended sediment finer than 62 micrometers were collected at 3-25 verticals at each of 8 river cross sections in the upper Illinois River Basin from March 1987 through September 1988. Cross-sectional coefficients of variation of temperature, specific conductance, and pH ranged up to 6 percent; cross-sectional coefficients of variation of the concentration of dissolved oxygen and the percentage of suspended sediment finer than 62 micrometers ranged up to 21 percent; and cross-sectional coefficients of variation of the concentrations of suspended sediment, fecal coliform, and chlorophyll ranged from 7 to 115 percent. Midchannel measurements of temperature, specific conductance, and pH were within 5 percent of mean cross sectional values of these properties at the eight sampling sites, most of which appear well mixed because of the effect of dams and reservoirs. Measurements of the concentration of dissolved oxygen at various cross-section locations and at variable sampling depths are required to obtain a representative value of this constituent at these sites. The large variability of concentrations of chlorophyll and suspended sediment, and fecal coliform counts at the eight sampling sites indicates that composite rather than midchannel or mean values of these constituents are likely to be most representative of the channel cross section.
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