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|Title:||Water quality studies : Hartwell Lake 1991 summary report|
|Authors:||Jabour, William E.|
Carroll, Joe H.
|Keywords:||Water quality management--Hartwell Lake (S.C. and Ga.)--Environmental aspects|
Hartwell Lake (S.C. and Ga.)
|Publisher:||Environmental Laboratory (U.S.)|
U.S. Army Engineer Waterways Experiment Station.
|Series/Report no.:||Miscellaneous Paper (U.S. Army Engineer Waterways Experiment Station.) ; EL-93-20|
|Abstract:||Hartwell Lake, located between Georgia and South Carolina along the Savannah River basin, was the site of an extensive water quality study during 1991. Temporal and longitudinal trends were identified through monthly in situ monitoring and bi-annual chemical analyses. The onset of thermal stratification began on Hartwell Lake during late March. By May, extensive stratification was present from headwaters to the forebay. Anoxic conditions were first observed in the middle reaches of the Seneca and Tugaloo River embayments during the July sampling. The greatest concentrations of chemical constituents within the tributary embayments were recorded during the mid- to late summer period. Progression of the anoxic zone from the mid-embayments towards Hartwell Dam was observed during the July through October period. Stratification and accompanying anoxia in the upstream regions were diminished by early October due to seasonal cooling and mixing processes. In the deepwater near-dam areas, anoxic conditions persisted until November. An intensive physicochemical sampling effort during July revealed the presence of increased concentrations of specific nutrients and organic carbons associated with anoxic conditions in the bottom waters of each tributary embayment. Chemical concentrations within the mid-reaches of the Seneca River embayment were consistently greater than those observed within the Tugaloo River arm. July was significant in that the sampling study coincided with the greatest monthly rainfall of the 1991 year. A second intensive sampling trip conducted in late October revealed that, due to autumnal mixing, anoxia within the tributary embayments no longer existed. Consequently, chemical constituents found in high concentrations within the Seneca and Tugaloo embayments during July were greatly diminished during October. Anoxic conditions were observed in the bottomwaters of the deep near-dam stations. Maximum concentrations of chemical variables were recorded in these areas during October. Continuous data for temperature, dissolved oxygen, pH and conductivity were collected using a Schneider RM-25 monitor in the tailrace below Hartwell Dam. These data reflected seasonal variability and were indicative of water quality conditions within the Hartwell Lake forebay. Hartwell Dam outflows during July and August 1991 were nearly double those for the same months during the previous year. This increased outflow was in response to greater than average rainfall. Inflows during August 1991 were three times greater than during August 1990. In summation, water quality conditions at Hartwell Lake were influenced by multiple factors, including hydrodynamics, loading, climatological conditions, seasonal variability, algal productivity, anoxic development and duration, bottom water-sediment interactions, and additional internal and external limnological processes. Studies conducted on two downstream Savannah River system lakes, Richard B. Russell and J. Strom Thurmond, recorded similar patterns of temporal and longitudinal gradients with regard to in situ and physicochemical parameters. Longitudinal, vertical and temporal variability were readily observed in temperature, dissolved oxygen, pH and specific conductance in situ data during 1991. Nutrient, organic carbon, and alkalinity concentrations were greatly influenced by the presence of anoxia in Hartwell Lake bottom waters.|
|Gov't Doc #:||Miscellaneous Paper EL-93-20|
|Appears in Collections:||Documents|