Separating the contributions of climate change and human activities to regional AET variability by using a developed analytical framework

Actual evapotranspiration (AET) is a key factor in land-atmosphere interactions and a major hydrological cycle component. Variations in AET have resulted from a combination of climate change (CC) and human activities (HA). Quantifying the contributions of these two factors to AET dynamics is essential for better understanding hydrometeorological and ecohydrological processes under both natural and anthropogenic conditions. In this study, an analytical framework was adopted for AET variance analysis, and the influences of CC and HA on regional AET variabilities were separated by using this method. AET variance is determined by the variance in CC ( σ AETc 2 ) and HA ( σ AETh 2 ); the former is estimated through a synthesis of the variance/covariance of potential evapotranspiration (ET 0 ) and precipitation (P), and the latter is determined from the residual between the total AET variance and σ AETc 2 . Based on a 36-year dataset (1980–2015), this framework is applied to the different regions of the Tao River Basin (TRB). The results reveal that climate was the primary factor influencing AET variance in most parts of the basin. Precipitation (P) dominated the σ AETc 2 and had a positive effect, while the interactions between P and ET 0 tended to suppress this effect, especially in the semihumid areas of the TRB. The contribution rates of CC and HA to basin AET variance were estimated to be 0.76 and 0.24, respectively. The developed analytical framework and its application are beneficial to the management and exploitation of water resources from the perspective of basin ecohydrology.