Quantifying the effect of vegetation greening on evapotranspiration and its components on the Loess Plateau

Abstract

As one of the largest revegetation projects in China, the Grain for Green Project has dramatically increased vegetation greenness (greening) on the Loess Plateau. Large-scale greening inevitably changed the spatiotemporal pattern of water availability on the Loess Plateau by increasing evapotranspiration (ET). Quantifying the effect of greening on ET is critical for regional water resources management and planning. This study uses the maximum entropy production (MEP) model and two attribution methods (the detrending and extending methods) to quantify the effect of greening on ET and its components (soil evaporation (Es) and transpiration (Et)) on the Loess Plateau from 2001 to 2018. The ensemble-averaged results of two attribution methods are used to reduce the potential uncertainty caused by the choice of attribution methods. The MEP model performs well in capturing the spatiotemporal variability of ET on both the site and basin scales. Greening significantly (p < 0.05) increases Et and decreases Es for the Loess Plateau, and the magnitude of increase in Et exceeds the magnitude of decrease in Es, leading to a nonsignificant (p > 0.05) increase in ET. The contribution of greening to mean annual Es, Et, and ET for the Loess Plateau is −16.6, 20.7, and 4.1 mm/yr, respectively. An increase in ET may further exacerbate water scarcity for the Loess Plateau.