Date of Award
Master of Science
Glenn A. Tootle
John S. Schwartz, Henri D. Grissino-Mayer
Tennessee Valley surface water is important to economic and population growth in the southeastern United States. By expanding streamflow records, water planners and managers can make decisions based on hydrologic events not appearing in current instrumental records. In the following research, monthly flow data from six USGS streamflow gages on the Clinch, Emory, Holston, and Nolichucky Rivers is used to create seasonal and annual streamflow seasons. Approximately 70 tree-ring chronologies across the Southeast U.S. are prescreened by length and correlation analysis against 38 streamflow seasons revealing that the May-June-July (MJJ) streamflow period displays the best tree-ring climate signal. The screened chronologies are then entered into stepwise linear regression, and R2 values for the six models range from 0.36 to 0.52. Reconstruction models range indicate estimation errors due to multicollinearity of the streamflow and tree-ring chronology datasets are minimal. The Durbin-Watson statistics indicate the model residuals do not autocorrelate, except for the Nolichucky River streamflow model, which may possess serial correlation. The positive values of the RE parameter indicate each of the models have statistical skill, and the RMSE parameter provides error ranges equal to 18 to 44% of the average observed instrumental flows. Based on the results, three gages, the Nolichucky, NF Holston, and SF Holston, were deemed acceptable. These models represent the first statistically skillful streamflow reconstructions in the Tennessee Valley. The reconstructions range from 209 to 295 years in length ending in 1980 and extending as far back as 1686. Examination of the reconstructions shows extreme drought in the 1770s. The wettest periods occurred from the 1970s to the mid-2000s. Other severe drought events occurred in the 1700s, the 1840s, and the early 1910s proving current records do not provide full accounts of Tennessee Valley streamflow variability.
Ogle, Ross William, "Streamflow Reconstructions in the Tennessee Valley Using Tree-Ring Chronologies. " Master's Thesis, University of Tennessee, 2010.