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Title: FACTORS AFFECTING SEDIMENT OXYGEN DEMAND DYNAMICS IN BLACKWATER STREAMS OF GEORGIA'S COASTAL PLAIN

Author
item UTLEY, BARBRA - University Of Georgia
item VELLIDIS, GEORGE - UGA
item Lowrance, Robert
item Smith, Matthew

Submitted to: Journal of the American Water Resources Association
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/4/2008
Publication Date: 6/1/2008
Citation: Utley, B., Vellidis, G., Lowrance, R.R., Smith, M.C. 2008. Factors affecting sediment oxygen demand dynamics in blackwater streams of Georgia's coastal plain. Journal of the American Water Resources Association. 44:724-741.

Interpretive Summary: Many coastal plain streams have poor water quality because of low dissolved oxygen (DO) levels at certain times of the year. These streams are called blackwater streams because the waters are dark-colored due to dissolved carbon from natural sources. Low dissolved oxygen can affect aquatic life, causing fish kills. These streams are required to have Total Maximum Daily Load (TMDL) plans that often include reduction of nutrient (nitrogen and phosphorus) loads. This approach assumes that low DO is due to excess algae growth in streams and that the algae growth is caused by excess nutrients. In many cases, the only sources of excess nutrients, if they exist, would be nonpoint source (diffuse) pollution from agriculture. TMDL plans have proposed nutrient load reductions up to 40% for both N and P from nonpoint sources. Stream DO levels are due to the complex interplay of biological and physical factors. Until recently, little information was available on the DO producing and consuming processes in these streams. Sediment Oxygen Demand (SOD) is believed to be an important process affecting dissolved oxygen concentrations in these streams. In this study, SOD was measured in seven blackwater streams of the Suwannee River Basin within the Georgia coastal plain for approximately 9 months. SOD was measured using four chambers that are placed over the stream bottom sediments in the field. SOD was found to vary significantly between the watersheds within the Suwannee River, however land use was not found to be the driving force behind SOD values. Results from this study will be used by the Georgia Department of Natural Resources – Environmental Protection Division as model input data for the development and evaluation of DO TMDLs in the Georgia coastal plain.

Technical Abstract: Many coastal plain streams have impaired water quality because of low dissolved oxygen (DO) levels at certain times of the year. These streams are required to have Total Maximum Daily Load (TMDL) plans that often include reduction of nutrient loads. This approach assumes that low DO is due to excess algal production that is stimulated by excess nutrients. In many cases, the only sources of excess nutrients, if they exist, would be nonpoint source pollution from agriculture. TMDL plans have proposed nutrient load reductions up to 40% for both N and P from nonpoint sources. Stream DO levels are due to the complex interplay of biological and physical factors. Until recently, little information was available on the DO producing and consuming processes in these streams. Sediment Oxygen Demand (SOD) is believed to be an important process affecting dissolved oxygen concentrations in blackwater streams of the southeastern coastal plain. Because very few data on SOD are available, it is common for modelers today to take SOD values from the literature for use with DO models. In this study, SOD was measured in seven blackwater streams of the Suwannee River Basin within the Georgia coastal plain for approximately 9 months. SOD was measured using four in-situ chambers, and was found to vary on average between 0.3-2.3 g O2m-2day-1 across the seven study sites. SOD was found to vary significantly between the watersheds within the Suwannee River, however land use was not found to be the driving force behind SOD values. Results from this study will be used by the Georgia Department of Natural Resources – Environmental Protection Division as model input data for the development and evaluation of DO TMDLs in the Georgia coastal plain.