Runoff reconstruction for the Bailong River from tree rings back to AD 1601, reveals changing hydrological signals of China north-south transition zone

We present a runoff reconstruction for the Bailong River based on the composite chronology developed from four sampling sites of Pinus tabulaeformis in the China north-south transition zone. The runoff reconstruction, spanning 1601-2013 CE, was developed by calibrating tree-ring data with the instrumental runoff record. Runoff reconstruction accounted for 44.3% of the actual runoff variance during the common period 1958-2010 and provided a long-term perspective on hydrological change in the China north-south transition zone. In the past 413 years, high- and low-runoff years accounted for 15.50% and 15.98%, respectively. Of all the 17 extreme hydrological events, 14 of them are extremely high-flow years, and 17th century was the wettest period during the past 413 years. The preliminary analysis results show that there is a relationship between our runoff reconstruction and the Atlantic Multidecadal Oscillation (AMO) at multidecadal scale. Since the 1990s, runoff in the China north-south transition zone has also seen a significant decrease as a result of dry trends of the source region.