Abstract: Hydrologic process on the southeast Tibetan Plateau(TP) under climate change is confronted with more uncertainty.A better understanding of streamflow characteristics as well as their spatial distribution and impact factors on the southeast TP will be critical to dealing with the influence exerted by climate change.In this study, we used the runoff and precipitation data to analyze streamflow characteristics and their spatial distribution via five hydrological signals i.e. averaged annual runoff depth, concentration degree, concentration time, baseflow index, and recession coefficient, and then investigated the related impact factors. Our results showed that in the southeast TP, annual runoff depth decreased from southeast (700-1 300 mm) to northwest (less than 400 mm), but concentration degree showed an opposite spatial distribution increasing from lower than 0.44 in southeast to above 0.59 in northwest. Both recession coefficient and baseflow index increased with elevation in lower altitude basins, ranging from 0.55 to 0.69 and from 0.51 to 0.73, respectively, while decreased in higher altitude basins, ranging from 0.74 to 0.72, and from 0.79 to 0.63, respectively. Impact factors showed noteworthy spatial difference in southeast TP basins. In lower altitude basins (average elevation approximately <3 000 m), precipitation was the main factor, whereas in higher altitude basins (average elevation approximately >3 000 m), only annual runoff depth and concentration degree were controlled by precipitation, while temperature and the underlying surface condition such as terrain and permafrost became the main factors of other characteristics. Since precipitation and permafrost conditions are susceptible to climate change, the time-spatial distribution of water resource in the southeast TP is prone to change, which needs sufficient attention.

Key words: streamflow characteristics, spatial distribution, impact factor, regession analysis, southeast Tibetan Plateau