Assessing the Impact of Vegetation Variation, Climate and Human Factors on the Streamflow Variation of Yarlung Zangbo River with the Corrected Budyko Equation

The Yarlung Zangbo River (YZR) is the largest river on the Qinghai Tibet Plateau, and changes in its meteorology, hydrology and vegetation will have a significant impact on the ecological environment of the basin. In order to deepen our understanding of the relationship of climate-vegetation-hydrological processes in YZR, the purpose of this study is to explore how vegetation growth in the YZR affects its runoff changes. We first identified the abrupt year of discharge in the YZR using a heuristic segmentation algorithm and cumulative anomaly mutation test approach. After that, the functional equation for NDVI and the Budyko parameter (n) was computed. Finally, the NDVI was introduced into the Budyko equation to evaluate the impact of vegetation changes on the streamflow in the YZR. Results showed that: (1) NDVI and discharge in the YZR both presented an increasing trend, and the mutation year of annual runoff in Nuxia station occurred in 1997. (2) n had a significant negative correlation with NDVI in the YZR (p < 0.01). (3) The contributions of Pr, ET0, NDVI, and n on streamflow change in the S2 period (1998-2015) were 5.26%, 1.14%, 43.04%, and 50.06%. The results of this study can provide scientific guidance and support for the evaluation of the effects of ecological restoration measures, as well as the management and planning of water resources in the YZR.

Automated summary

The purpose of this study is to explore how vegetation growth in the Yarlung Zangbo River affects its runoff changes. The results show that: (1) both the NDVI and discharge in the river exhibit an increasing trend, with the annual runoff mutation occurring in 1997. (2) The Budyko parameter (n) has a significant negative correlation with NDVI in the river. (3) During the period of 1998-2015, the contributions of precipitation, evapotranspiration, NDVI, and n to the streamflow changes in the river are 5.26%, 1.14%, 43.04%, and 50.06% respectively. These findings can provide scientific guidance and support for the evaluation of ecological restoration measures and the management of water resources in the Yarlung Zangbo River.