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THE CALIBRATION VALIDATION AND SENSITIVITY ANALYSIS OF GEORGIA DOSAG: AN IN-STREAM DISSOLVED OXYGEN MODEL

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

Citation:  Watershed Management to Meet Water Quality Standards and Emerging TMDL (Total Maximum Daily Load) Proceedings of the Third Conference 5-9 March 2005 (Atlanta, Georgia USA) Publication Date 5 March 2005  701P0105.(doi:10.13031/2013.18088)
Authors:   A. M. Cathey, G. Vellidis, M. C. Smith, R. Lowrance, and R. Burke
Keywords:   Dissolved oxygen, DoSag, calibration, validation, sensitivity analysis, long-term BOD, TMDL

Eighty four percent of dissolved oxygen (DO) impaired streams in Georgia occur within five physiographic regions: the Tifton Upland, Vidalia Upland, Okefenokee Basin, Bacon Terraces, and the Barrier Islands Sequence. Such a high number poses the question; is the average daily level of DO in these streams naturally less than the water quality standard of 5.0 mg L-1? Streams in southern Georgia display several characteristics causing low levels of DO. Typically, the streams have low gradient channels, experience high temperatures and low to zero flow in the summer, and initial evidence shows that sediment oxygen demand (SOD) may be high.

Georgia DoSag version 2.1 has been used by the Georgia Environmental Protection Division to model DO and develop Total Maximum Daily Loads (TMDLs) in the Altamaha River Basin. DoSag will continue to be used to model DO as a part of Georgia’s TMDL program. The objective of this research was to determine the applicability of DoSag in coastal plain streams. This paper describes the parameter estimation, calibration, sensitivity analysis, and validation of the DoSag model in the Little River Experimental Watershed (LREW), located in the coastal plain of Georgia. The result of this paper describes a matrix of dominant causes of low DO conditions in the LREW including SOD, reaeration, temperature, and streamflow. An understanding of natural versus anthropogenic causes for low DO will not be fully understood until SOD and reaeration in Georgia’s coastal plain are measured.

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