Abstract: Tailoring ecological restoration policies to local conditions, such as determining whether to prioritize afforestation programs or grassland restoration, is critical for the sustainable implementation of China’s Grain for Green Project (GGP). However, there remain significant knowledge gaps to understanding the divergent hydrological responses of these programs. This study integrates remote sensing and meteorological data to detect spatiotemporal variations of evapotranspiration and its influencing factors. The eco-hydrological dynamics between two distinct vegetation restoration zones are compared: the northwestern region (grassland restoration) and the southeastern region (afforestation). After implementation of the GGP, a notable greening trend with a significant increase in leaf area index was observed, exhibiting spatial heterogeneity in both regions. At the same time, evapotranspiration showed a distinct NW–SE increasing gradient. Regional drivers also diverged: evapotranspiration in the southeast was primarily leaf area index-driven, while in the northwest, it was controlled by precipitation-to-potential evapotranspiration ratios. This water-carbon coupling disparity amid regional climate variability caused contrasting water yield declines, significant in the southeast compared to the insignificant yields in the northwest. This study contrasts forest versus grassland restoration at a regional scale. The findings underscore ecohydrological feedbacks from ecological restoration, advocating spatially adaptive ecosystem management to balance water-carbon trade-offs.

Key words: Grain for Green Project (GGP), Afforestation and grassland restoration, Evapotranspiration, Ecohydrological feedbacks, Leaf area index · Loess Plateau