Abstract: Under the influences of climate change and human activities, the Nenjiang River basin has suffered floods and droughts frequently. This study constructs a distributed hydrological model for this basin and a set of standard runoff drought indexes (SRIs) over various time scales, using its 1980-2013 runoff data measured at the hydrological stations of Shihuiyao, Tongmeng, Jiangqiao, and Dalai. Coupling the Budyko theory and the hydrological simulation method, we conduct an attribution analysis on the changes in its runoff and hydrological drought characteristics caused by the construction and operation of the Nirki reservoir. And how the hydrological drought will evolve in the future is explored using the Coupled Model Intercomparison Project in the sixth phase (CMIP6). Our findings reveal that on an annual scale, human activities are the dominant factor contributing as much as 80% to runoff evolution. The hydrological drought characteristics in the basin manifest a general trend of intensification from its upstream to downstream, with its upstream region primarily influenced by climate change and downstream region by human activities. Under future climate scenarios, its SRI sequence demonstrates an intensified volatility with an alternating dry and wet pattern; its drought duration will be increasing, indicating an elevated risk of future drought in the whole basin.

Key words: attribution analysis, hydrological drought, Coupled Model Intercomparison Project in the sixth phase (CMIP6), Nenjiang River basin