We report on research to develop quantitative, annually resolved, multi-century, tree-ring reconstructions of streamflow for 12 interstate river systems in eight states (Alabama, Florida, Georgia, Louisiana, Mississippi, North Carolina, South Carolina, and Virginia) in the South Atlantic Gulf Basin (AGB) of the southeastern United States.
We used a nested principal components regression method to develop annually resolved tree-ring reconstructions of warm-season (March-October streamflow for the 12 interstate rivers and select tributaries, for the past ~300-1,000 years, in the AGB. These reconstructions explain between 30 and ~70% of the instrumental streamflow variance at multiple instrumental gages. Our reconstructions demonstrate that recent multi-year average flows (~2000 to present) were in many cases among the lowest in the ~1,000-year record, and although consumptive withdrawals may exacerbate low flow conditions, observed regional precipitation and streamflow from unimpaired gages display substantially similar decadal declines to those shown in the tree-ring reconstructions.
This research will provides insight into not only the long-term variability of streamflow, but also sheds light on the associated physical, social, economic and ecological impacts this variability has on coastal watersheds in the AGB and SE U.S. Improved understanding of streamflow variability will directly benefit the development of water policy in the SE, by informing a variety of socially and economically relevant areas related to water withdrawals, streamflow variability, and drought and flood mitigation.