Sediment Oxygen Demand of Coastal Plain Blackwater Streams

Abstract

Sediment Oxygen Demand (SOD) has become and integral part of modeling dissolved oxygen within surface water bodies. Because very few data on SOD are available, it is common for modelers today to take SOD values from the literature for use with dissolved oxygen (DO) models. SOD is such an important parameter in modeling DO that this approach may lead to erroneous results. This paper reports on an extensive study to quantify SOD in blackwater streams of the Georgia coastal plain. In-situ SOD measurements are made in the Upper Suwannee, Alapaha, Little River, and Withlacoochee river basins. The subwatersheds within which SOD measurements are taken are chosen to vary from 3000-7000 ha in area and are classified as predominantly forested or predominantly agricultural. SOD is measured using four in-situ chambers. In addition to SOD measurements, a particle size analysis is completed on the sediment and water flow is measured at each site. The result of this paper connects SOD values to specific sediment composition and land use properties. By recording percent sand, silt, clay, organics, and flow, SOD values recorded in one region may be applied to similar conditions in another region. Results from this study will be used by the Georgia Department of Natural Resources – Environmental Protection Division as input data to their Georgia DO Sag model which is used to develop DO TMDLs or evaluate already developed DO TMDLs in the Georgia coastal plain.