Runoff variations affected by climate change and human activities in Yarlung Zangbo River, southeastern Tibetan Plateau

Abstract

The runoff in Tibetan Plateau (TP) is sensitive to environmental changes, and it is thus challenging to assess the variations and influencing factors of runoff in the context of global warming and increased human activities. We addressed this challenge by using the most comprehensive dataset, Budyko hypothesis, and wavelet theory to attribute runoff variations in the Yarlung Zangbo River Basin (YZRB), and its interaction with regional environmental variables (e.g., precipitation PCP, relative humidity RH, average temperature TMPave, maximum temperature TMPmax, minimum temperature TMPmin, wind speed WS, snow depth SD, potential evapotranspiration ET0, and normalized difference vegetation index NDVI). The results indicated that, 1) the warming of the YZRB was 0.47, 0.36, and 0.65 °C/decade in TMPave, TMPmax, and TMPmin, two to three times the global mean rate, and the increasing trend of precipitation was nonsignificant; 2) ET0 increased significantly by 2.25 mm/decade, and SD decreased rapidly at a rate of 2.54 mm/decade. 3) The streamflow (lower Nuxia) showed a decreasing trend from 1960 to 2015, primarily caused by climate change, which accounted for 78.81%. Human activities contributed 21.19%; 4) Seasonal streamflow increased in Spring and Winter and declined in Summer and Autumn. 5) PCP was the single variable mostly associated with runoff. When PCP-SD and PCP-RH-ET0 were combined, they demonstrated the most robust relationships with runoff, respectively; 6) A modest increase in PCP and accelerating snowmelt may not offset water dissipation due to severe warming. Further research is necessary to improve understanding of the driving mechanisms behind seasonal and inter-annual variability in the runoff and to provide strategies for mitigation and adaptation to environmental change.