CR prepress abstract  -  DOI:

Runoff variations at the source of the Yangtze River over the past 639 years based on tree-ring data

Jinjian Li, Xuemei Shao, Ningsheng Qin*, Yuanyuan Li


ABSTRACT: Tree-ring width data collected at five sites near the source of the Yangtze River were used to construct a comprehensive regional chronology in this study. The tree-ring widths exhibited a significant positive correlation with the runoff in the source area of the Yangtze River in multiple months. The correlation between tree-ring width and the annual runoff (calculated from the previous September to the current August) was the most significant (r = 0.665, n = 56, p < 0.0001). A record of the annual runoff of the Yangtze River from 1374-2012 at its source was then reconstructed. The reconstruction equation was stable and explained 44.2% of the variance (R2adj = 43.2%, n = 56, F = 42.86). As indicated by the reconstruction, 17 periods of high flow and 14 periods of low flow occurred during the previous 634 years. The longest periods of high flow occurred during 1615-1643 and 1755-1783, while the longest period of low flow occurred during 1445-1490. The wet and dry periods in the reconstruction coincided with similar periods identified in a time series of Palmer drought severity index (PDSI) values obtained near the research area and a time series of reconstructed streamflow in the upper Yellow River. Several important periods of low flow also coincided with periods of drought that affected broader regions. An analysis using the multi-taper method (MTM) demonstrated that periodic variations in runoff of 2-5 years, c. 20 years, and, c. 50 years have occurred at the source of the Yangtze River. Moreover, the relationships between annual runoff and solar activity and the intensity of the southwest Asian summer monsoon (SASM, also known as the Indian monsoon) are discussed in this article.