Effects of forest cover change on catchment evapotranspiration variation in China

Several large-scale revegetation programs in China have resulted in significant changes in forest cover (Delta F) during the past three decades. As forests have important effects on catchment hydrology, evaluating the effects of Delta F on hydrology is essential. Using data from 44 catchments across China, this study derived a rational analytical equation to link changes in actual evapotranspiration (Delta ET) with those in F within the Budyko framework, and further quantified the effects of Delta F on ET variation during 1976-2015. The elasticity of ET to Delta F was found to be the greatest in the dry catchments in northwest China, followed by the humid catchments in south China, and was the smallest in the subhumid and semiarid catchments in north China. F averaged across all the catchments has increased, and has further led to the increase in ET. The F-ET relationship has become more prominent in the recent decade (2006-2015), with 68.0% of the catchments showing an average increase in F of 4.5% and a resultant average increase in ET of 8.2% compared with the baseline period (1976-1985). These results are helpful for quantitative assessment of hydrological responses to afforestation, especially in water-limited regions.