Spatiotemporal variability and trends in the hydrology of the Xiang River basin, China: extreme precipitation and streamflow

It has been widely recognised that climate changes have significant impacts on hydrological processes and may increase flood risk. In the past 20 years, a frequent occurrence of heavy floods across the Xiang River basin (XRB) was witnessed, a major tributary of the Yangtze River basin (YRB), China. This study quantified impacts of precipitation extremes on streamflow changes across the XRB at annual and seasonal scales using the Mann–Kendall trend test (MK) method and continuous wavelet transform (CWT). Besides, the cross-wavelet transform (XWT) and wavelet coherence (WTC) methods were employed to identify the correlations between extreme precipitation and streamflow. The results indicated no significant trends in annual rainfall and/or streamflow, while the increasing trends in the summer extreme rainfall and streamflow can be observed in the upper and middle XRB. Results by the XWT and WTC indicated highly similar patterns of signal changes at 1–4 and 5–12 years from the 1980s to 2005, between extreme precipitation and streamflow in the upper and middle river basin. Nevertheless, the changes in extreme precipitation in the lower reaches do not always coincide with the extreme streamflow variations. The coherence between extreme precipitation and river flows gradually declines from the upper to the lower basin.