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The majority of streams listed on the 2001 303(d) list in the Coastal Plain of Georgia are in violation of dissolved oxygen (DO) standards established by the Georgia Department of Natural Resources. The highest percentage of DO-impaired streams occurs in the southern Coastal Plain of Georgia (Ochlockonee, Suwannee, Satilla, and St. Marys River Basin Group) where 61 of 67 or 91% of listed streams are in violation of the DO standard. The current Georgia DO standard for most designated uses is a daily average of 5.0 mg/L and a minimum of 4.0 mg/L. Research by University of Georgia and USDA-ARS scientists in 3 Coastal Plain watersheds indicates that low DO in Coastal Plain streams may be a natural condition for summer months. Consequently, it appears that the established State DO standard may not be applicable to Coastal Plain streams particularly during the extended summer period. To address this issue, Georgia DNR-EPD is proposing a new DO standard which will be 90% of natural DO during critical flow conditions. Application of this new standard requires some means of establishing natural DO during critical flow conditions. Yet, an extensive data set which can be used to calculate this parameter for a wide range of streams is currently not available. To allow for a science-based standard, we initiated an extensive research program to establish the natural range of DO at critical flow conditions in the Coastal Plain of Georgia. The project contains monitoring and modeling aspects. Monitoring is taking place in the Ochlockonee, Suwannee, Satilla, and St. Marys river basins.