Evapotranspiration (ET) has undergone profound changes as a result of global climate change and anthropogenic activities. The construction of the Three Gorges Reservoir (TGR) has led to changes in its land use/land cover (LUCC) and local climate, which in turn has changed ET processes in the TGR region. In this paper, the CLM4.5 land surface model is used to simulate and analyze the spatiotemporal variability of ET between 1993 and 2013. Four experiments were conducted to quantify the contribution rate of climate change and LUCC to changes in ET processes. The results show that the climate showed a warming and drying trend from 1993 to 2013, and the LUCC indicates decreasing cropland with increasing forest, grassland, water bodies and urban areas. These changes increased the mean annual ET by 13.76 mm after impoundment. Spatially, the vegetation transpiration accounts for the largest proportion in ET. The decreasing relative humidity and increasing wind speeds led to an increase in vegetation transpiration and ground evaporation, respectively, in the center of the TGR region, while the LUCC drove changes in ET in water bodies, urban areas and high-altitude regions in the TGR region.

Since 2000, the vegetation cover in the Yellow River Basin (YRB) has significantly increased. However, the responses of carbon and water cycles to large-scale vegetation recovery in the basin and their driving mechanisms remain unclear. This study employs methods such as Sen’s slope trend test, partial correlation analysis, residual analysis, and interpretable machine learning models to investigate the variations in gross primary productivity (GPP), evaporation (ET), and water use efficiency (WUE) in the YRB. It aims to reveal the spatial differentiation mechanisms that drive GPP, ET, and WUE. The results indicate the following: (1) From 2001 to 2020, significant increasing trends were observed in GPP, ET, and WUE across the YRB (p < 0.05), with the most pronounced vegetation recovery observed in the middle reaches. (2) GPP, ET, and WUE are most strongly correlated with the Leaf Area Index, with median values of 0.78, 0.30, and 0.70, respectively. (3) On average, climate change contributes spatially 24.8%, 35.6%, and 24.3% to GPP, ET, and WUE, respectively, while human activities contribute, on average, 75.2%, 64.4%, and 75.7%. (4) Regarding their synergistic evolution, GPP changes predominantly drive WUE changes in the YRB relative to ET. (5) The contributions of NDVI changes to WUE, GPP, and ET changes are 60.4%, 73.1%, and 14.9%, respectively. Overall, NDVI changes dominate the changes in GPP and, by extension, in WUE. This research sheds light on the pathways toward ecological restoration and sustainable development in the YRB.