Tree-Ring Reconstructions of Streamflow for the Tennessee Valley

Anderson Anderson,Tootle Tootle,Ogle Ogle,Oubeidillah Oubeidillah

doi:10.3390/hydrology6020034

Abstract

This study reports the preliminary results from a statistical screening of tree-ring width records from the International Tree-Ring Data Bank (ITRDB), to evaluate the strength of the hydrological signal, in dendrochronological records from the Tennessee Valley. We used United States Geological Survey (USGS) streamflow data from 11 gages, within the Tennessee Valley, and regional tree-ring chronologies, to analyze the dendroclimatic potential of the region, and create seasonal flow reconstructions. Prescreening methods included correlation, date, and temporal stability analysis of predictors to ensure practical and reliable reconstructions. Seasonal correlation analysis revealed that large numbers of regional tree-ring chronologies were significantly correlated (p ≤ 0.05) with the May–June–July streamflow. Stepwise linear regression was used to create the May–June–July streamflow reconstructions. Ten of the 12 streamflow stations were considered statistically skillful (R2 ≥ 0.40). Skillful reconstructions ranged from 208 to 301 years in length, and were statistically validated using leave-one-out cross validation, the sign test, and a comparison of the distribution of low flow years. The long-term streamflow variability was analyzed for the Nolichucky, Nantahala, Emory, and South Fork (SF) Holston stations. The reconstructions revealed that while most of the Western United States (U.S.). was experiencing some of its highest flow years during the early 1900s, the Tennessee Valley region was experiencing a very low flow. Results revealed the potential benefit of using tree-ring chronologies to reconstruct hydrological variables in the Southeastern U.S., by demonstrating the ability of proxy-based reconstructions to provide useful data beyond the instrumental record.

Highlights

Water planners and managers can make more accurate decisions based on information provided by the expanding hydrological records
Little dendroclimatological research has been conducted within the Southeastern U.S during the past 20 years, when compared to the number of studies conducted in the Southwestern, Northwestern, and Rocky Mountain regions of the U.S In the Southeastern U.S, many misconceptions still linger among scientists that tree-ring research is not possible due to the high decomposition and decay rates, a lack of trees that are long-lived, and the absence of climatically sensitive patterns of tree rings to facilitate cross-dating [5]
As theexamined reconstruction length and across moisture sensitivity of Eastern tree species were unknown at the time ofValley data collection, we initially examined 102 chronologies across 12 states (Figure 1), for the the strength of their responses to the Tennessee Valley streamflow

Summary

Introduction

Water planners and managers can make more accurate decisions based on information provided by the expanding hydrological records. Tree rings have been widely used as a proxy to reconstruct hydrological variables in the Western United States (U.S.) [1,2,3,4]. The limited number of reconstructions for the Southeastern U.S can be explained by several factors. The effects of the topography may explain why tree-ring chronology to a streamflow gage is not always indicative of a statistically significant streamflow–tree-growth relationship. The Southeastern U.S receives more precipitation than most parts of the country, especially when compared to the Western U.S, providing less motivation for water quantity studies. The lack of streamflow gage and tree-ring datasets spanning cooperative lengths, contributes to the difficulty of obtaining long calibration windows

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Conclusion