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Dissolved Oxygen Concentrations in Three Coastal Plain Watersheds: Implications for TMDL's

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  Pp. 606-610 in Total Maximum Daily Load (TMDL) Environmental Regulations: Proceedings of the March 11-13, 2002 Conference, (Fort Worth, Texas, USA)  701P0102.(doi:10.13031/2013.8973)
Authors:   David Bosch and Richard Lowrance George Vellidis

Monitoring data developed by the State of Georgia show widespread violations of water quality standards in the Suwannee River Basin due to low dissolved oxygen (DO). TMDL modeling for the impaired streams indicates an average 40% load reduction for Total N and Total P is necessary to relieve the DO impairment. These estimates assume nutrient enrichment is causing excessive algal growth that leads to depleted DO. Because many of the impaired streams do not have point source discharges, these load reductions will need to come from reductions in nonpoint sources, primarily agriculture and silviculture. The GA DNR-Environmental Protection Division sets standards for the various designated uses of the statess surface waters. For fishing, which is the designated use of most rivers in the Georgia Coastal Plain, the DO standard is an average of 5.0 mg L -1 or a minimum of 4.0 mg L -1 . Dissolved oxygen data have been collected at 21 sites in three watersheds in South-central Georgia for four years. DO concentrations observed from 1997 to 2001 ranged from 0.4 mg L -1 to 20.8 mg L -1 . Six measurement sites were found to be below state standards for streams supporting fish. Statistical correlations between DO and other measured parameters, including temperature, pH, conductivity, oxidation-reduction potential, turbidity, and flow depth, were poor. However, there was some indication that low DO levels coincided with periods of low flow. Additional data is necessary to evaluate these relationships and natural levels of DO in streams.

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