Knowledge Bank

Dissolved oxygen (DO) concentrations in the summer of 1987 did not change significantly along the Ohio River between Wheeling, WV and Louisville, KY. Depth variation was evident but no temperature stratification was observed. DO concentrations downstream of hydroelectric dams decreased in each case. Degassing of the water passing through the turbines may have accounted for this decrease. No correlation was found between DO concentration and volume of effluent discharged from waste water treatment plants (WWTP). Elevated DO concentrations existed at and below WWTPs, indicative of the general effectiveness of WWTP reaeration on DO concentrations at the point of discharge and approximately one mi down river. WWTPs in the highly urbanized Cincinnati area yielded results similar to the WWTPs as a whole, but a slight sag was evident at the Dry Creek WWTP. A hypothetical grab-sample taken at 1.5 m depth at mid-channel was compared to the mean obtained from a nine-sample-profile. The variation was not significant, indicating that grab-sampling would be equivalent to more detailed and expensive profile sampling under similar flow conditions in the river.