Submitted to: Watershed Management Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 11/5/2001
Publication Date: 3/11/2002
Citation: Bosch, D.D., Lowrance, R.R., Vellidis, G., Sheridan, J.M., Williams, R.G. 2002 Dissolved oxygen concentrations in three coastal plain watersheds: implications for tmdl's. Watershed Management Conference Proceedings of the Total Maximum Daily Load (TMDL) Environmental Regulations Conference. Ali Saleh (ed). Fort Worth, Texas, March 11-13, 2002. pp. 92. Interpretive Summary: Adequate concentrations of dissolved oxygen (DO) in the water are necessary for fish life and other aquatic organisms and the prevention of offensive odors. DO levels are considered the most important and commonly employed measurement of water quality and an indicator of a water body's ability to support desirable aquatic life. Monitoring data developed by the State of Georgia show widespread violations of water quality standards in the Suwannee River Basin due to low DO. The factors which contribute to the low DO are poorly understood. Dissolved oxygen data were collected at 21 sites in three watersheds in South-central Georgia for four years. Six out of the 21 sites were found to be below state standards for streams supporting fish. Low flow and high temperature conditions appeared to contribute to the low DO conditions. These data are critical for determining background DO conditions and for determining the factors controlling oxygen depletion in streams throughout the U.S. The data will assist in the development of effective land management programs for improving and maintaining stream water quality.
Technical Abstract: 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 states's 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 fou 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.