The coupling impact of climate change on streamflow complexity in the headwater area of the northeastern Tibetan Plateau across multiple timescales

Abstract

The streamflow from the headwater areas of the Tibetan Plateau (TP) provides critical support for downstream regions, yet understanding of the streamflow complexity on the TP, which is essential for hydrological modeling and water resource management, remains scarce. This study aims to measure streamflow complexity in the headwater areas of the TP and investigate the coupling effects of climatic variables (i.e., precipitation and air temperature) on the streamflow complexity across multiple timescales. Using daily streamflow records, we employ permutation entropy as the measure of annual streamflow complexity in the upper Heihe River (UHR) watershed in the northeastern TP from 1960 to 2014. Additionally, wavelet coherence is applied to evaluate the impact of climate (i.e., precipitation and temperature) change. Our results show: (1) due to climate change, streamflow complexity has significantly increased since 1972 in the UHR watershed; (2) the periods of warmer and wetter weather have a longer-term influence on streamflow complexity. Specifically, before 1972, dryer, colder weather in the TP would significantly affect the complexity of the streamflow every three to four years, but after that date, these climatic events occurred less frequently, with gaps of between eight and twelve years, during which the weather was much warmer and wetter; and (3) the influence of precipitation on the streamflow complexity decreased, while that of air temperature increased. Therefore, the impact of climate change on streamflow complexity relating to the dynamic structure of streamflow should be regarded as significant to the work of hydrologists and water resource management agencies.