Clarification of dominating drivers for streamflow changes in the upper reach of Mekong River Basin

Study region: Lancang River Basin (LRB)Study focus: Previous studies provided different results in terms of the roles played by climate change and human activities, leaving a knowledge gap in the complex streamflow variability and its physical causes in LRB. In the study, a Budyko framework-aided analytical approach was applied to explore the streamflow decrease in LRB and its physical causes, by especially clarifying the different performances of eight Budyko equations and the influences of diverse baseline periods.New hydrological insights for the region: Results revealed that the four parametric Budyko equations can provide proper parameters to reflect changes in catchment characteristics (including human activities) and their influences, and thus, they performed better than the four non-parametric Budyko equations. It was further found that more reasonable attribution results of streamflow change were obtained when a longer baseline period (at least 20 years) was used. Results also indicated that human activities (accounting for-158.9%) dominated the streamflow decrease during the transition period (1986-2004), by offsetting the positive effects of climate change (accounting for 58.9%). During the impact period (2005-2015), human activities (accounting for-65.6%) still dominated the streamflow decrease, and climate change (accounting for-34.4%) further aggravated the streamflow decrease in LRB.