Runoff change point detection and its association with monsoons in the Lancang-Mekong River Basin

Climate change has substantially altered the variability of runoff in the Lancang-Mekong River Basin (LMRB) over the last few decades. Previous studies have analysed the trend of runoff in the LMRB in detail. However, little is known about the spatial distribution of runoff change points and its association with the attribution analysis, in which change point plays a key role when assessing the impacts of climate change and human interventions on runoff. In this study, the spatial distribution of change points for runoff and precipitation as well as their relation to monsoon indices in the LMRB are investigated. We found that the change points for both runoff and precipitation show a trend of occurring earlier from upstream to downstream in the lower LMRB. In addition, the hydrological processes were significantly influenced by monsoon fluctuation. The western North Pacific summer monsoon has significantly influenced runoff (precipitation) over the southeastern basin with 39.6% (34.6%) explained variance, whereas the Indian summer monsoon has predominantly influenced the mid-low area of the basin with 48.4% (40.8%) explained variance. The comprehensive effects of the change points of monsoon indices contributed greatly to the abrupt change of precipitation in the overlapped region such as the mid-low LMRB. Our findings indicate that understanding the mechanism of monsoon fluctuation on abrupt changes in streamflow, runoff, and precipitation in the basin will offer a better understanding of climate change impacts on water resources, which can provide support for optimizing forecasting and improving water resources management in the basin.