Impact ways and their contributions to vegetation-induced runoff changes in the Loess Plateau

Sixteen typical watersheds with long-term continuous runoff monitoring within the Loess Plateau (100°54′∼114°33′E, 33°43′∼41°16′N), Northwest China. Focusing on the period before and after implementing China's "Grain-for-Green" Program (GFGP) (started in 1999), this study analyzed runoff and vegetation changes and how the latter affects the former. The results show that the vegetation change effect was the main driver of runoff reduction over the LP from 1982–1999 to 2000–2015 and accounted for 78.94% (59.71–97.25%) of the reduced runoff. Changes in vegetation under multiple anthropogenic and natural influences are mainly characterized by increases in greenness, growing season length, and woodland and grassland area (along with a decrease in cultivated area). These changes have altered the repartition of precipitation in favor of evapotranspiration rather than runoff. The GFGP-led LULC shift, particularly the reduction of cropland, plays a vital role (GRD > 0.80) in vegetation-induced runoff losses, which may exacerbate future water stress in the region. To curb the LP's continuous attenuation of river runoff and promote the Yellow River Basin's ecological protection and high-quality development, we suggest focusing on the vegetation change effects on runoff and optimizing afforestation measures.