Simulation of Actual Evapotranspiration and Its Multiple-Timescale Attribution Analysis in the Upper Reaches of the Jinsha River, China

For quantifying the contribution rates of climatic variation and anthropogenic activities on the actual evapotranspiration at multiple timescales in the URJR, based on the monthly meteorological and hydrological data of the URJR, this study first used the BG mutation method to determine mutation years of runoff depth to divide the research period into base and variation periods. Then, the ABCD hydrological model was used to simulate the runoff variation process during the base period and the variation period, and the actual evapotranspiration data at the monthly scale was simulated. Finally, a multiple-timescale Budyko model was applied for quantitatively computing the impacts of climatic variation and anthropogenic activities on multiple-timescale actual evapotranspiration in the URJR. The results demonstrated the following: (1) The mutation years of runoff depth at the Batang and Shigu hydrological stations were 1988 and 1987. (2) The actual evapotranspiration at multiple timescales (quarterly and monthly) in the upper reaches of the Jinsha River all presented a significant increase (p < 0.01), with a growth rate ranging from 0.02 mm/a to 0.22 mm/a. (3) Climatic variation is dominant factor leading to actual evapotranspiration growth at multiple timescales (quarterly and monthly) at the Batang Hydrological Station, with a contribution ranging from 0.71 mm to 8.50 mm. (4) Human activities are dominant factors leading to actual evapotranspiration growth at multiple timescales (quarterly and monthly) at the Shigu hydrological station, with a contribution ranging from 0.60 mm to 9.62 mm.