Spatial disparity in runoff variability between Southwestern China's River Basin headwaters during 1981-2020
Headwaters of China's southwestern river basins,including headwaters of the Yarlung Zangbo,Nujiang,Lancang,Yangtze,and Yellow river basins,are nestled in the southeastern part of the Tibetan Plateau and highly sensitive to climate change.These river basins play a pivotal role as vital freshwater sources for China and neighboring Southeast Asia countries,and have important impacts on downstream agricultural irrigation,hydropower,and ecological and environmental stability.In recent decades,the Tibetan Plateau has generally experienced a warming and wetting climate,which could alter runoff trends and variability over headwaters of China's southwestern river basins.Most previous studies explored runoff changes over a typical basin of headwaters of China's southwestern river basins,but they lack the analysis of the spatial disparities and driving mechanisms of runoff changes across the headwaters of China's southwestern river basins.Recent studies used proxy sets of paleoclimate data to extract low-frequency signals of changes in climate variables over the eastern Tibetan Plateau,and revealed some north-south symmetrical changes of hydrological variables in some historical periods.These studies implied that there could exist north-south disparities in the response of meteorological and hydrological variables to climate change over headwaters of China's southwestern river basins,but the underlying climate mechanisms need to be further investigated.In particular,over the past four decades when the Tibetan Plateau showed significant changes in regional hydrothermal conditions,there is still a lack of comprehensive understanding of spatial disparity in runoff variability between headwaters of China's southwestern river basins.This study integrates observed runoff data,reanalysis information,and remote sensing retrievals to examine the spatial disparity in runoff variability and their underlying climatic mechanisms across the headwaters of China's southwestern river basins from 1981 to 2020.We analyzed runoff trends and abrupt changing years,annual runoff variations responding to precipitation variations,changes in the westerly-monsoon atmospheric circulations represented by the defined westerly and monsoon indices,and spatial patterns of water vapor changes.Our findings show the following insights:(1)A distinct change occurring at the end of the 20th century(1997)in the southern portion(comprising the headwaters of the Yarlung Zangbo and Nujiang River basins),and in the early 21st century(2004-2007)in the northern portion(encompassing the Sanjiangyuan basin,inclusive of headwaters of the Lancang,Yangtze,and Yellow River basins).(2)Precipitation emerges as a pivotal influencer of runoff variations,with an abrupt change year in runoff similar to that of precipitation and a strong correlation exceeding 0.8 across all basins.(3)Driven by shifts in the westerly-monsoon circulation,which points to the weakening of the South Asia Summer Monsoon and the strengthening of the westerly,the spatially heterogeneous distribution of water vapor and precipitation facilitated the transition of runoff trends around year 2000.Southern basins witnessed an increasing trend,followed by a decline,while northern basins demonstrated an inverse trajectory in both periods.In summary,our study reveals substantial spatial divergence in runoff behavior across China's southwestern river basins over the last four decades,characterized by contrasting annual runoff trends between the southern and northern basins.This hydrological variability is primarily attributed to shifts in atmospheric circulation patterns influencing water vapor and precipitation dynamics.This study could enhance our understanding of hydrological responses to climate change over the headwaters of China's southwestern river basins,providing valuable insights on water resources management over this vulnerable region.
runoff variationheadwaters of China's southwestern river basinswesterly-monsoon systematmospheric water vaporprecipitation
万方数据
维普
