Runoff spatiotemporal variability driven by climate change and human activity for the Nianchu River Basin in Southwestern Tibet

Nianchu River Basin (NRB), a key agricultural area on the Tibetan Plateau in China. Runoff is recognized as the most important outcome of water resources management, playing a crucial role in both ecology and hydrology. This study analyzes the spatiotemporal variability of runoff in the NRB over the past 48 years and further quantify the impacts of climate conditions, vegetation cover, and irrigation water withdrawal (IWW) on runoff changes. This study aims to improve our understanding of the mechanisms driving runoff changes in alpine mountains. The results indicate that the runoff in the NRB has significantly declined by −0.21 mm per decade. The effects of the various influences on runoff are non-stationary at the spatiotemporal scales, with precipitation (Pre) and temperature (Tmp) as the main factors, and Pre consistently contributing the most to changes in runoff until 2002. However, over time, the contribution of Pre has significantly declined. After 2002, the contribution of Tmp gradually became comparable to that of Pre and eventually surpassed it. IWW extraction generally exerts adverse effects, and in areas with poorer vegetation in NRB, NDVI changes significantly impact runoff. Under the context of global warming and increasing human activities, Tmp and IWW have shown a growing adverse impact on basin runoff, offering new insights for water resource management. • Runoff in the NRB exhibited a decreasing trend from 1970 to 2017. • Spatial patterns of runoff variability change disruptively around 2000. • Temperature and human activity will dominate the reduction in runoff. • Influencing factors' spatial patterns change dynamically over time.