Estimating the Increase in Regional Evaporative Water Consumption as a Result of Vegetation Restoration Over the Loess Plateau, China

One of the world's largest revegetation programs, the Grain for Green Project (GfGP), has been taking place on the Loess Plateau of China since 1999. Such massive revegetation causes changes in the region's hydrological cycle, water availability, and ecological sustainability through enhanced evapotranspiration (ET). Here we quantify effects of the GfGP's revegetation on ET over this water-stressed region. Our approach involves use of a modified Priestley-Taylor Jet Propulsion Laboratory (PT-JPL) model, incorporating vegetation dynamics as a new component. The original PT-JPL model has been expanded from site scale to regional scale, thereby allowing its application to the Loess Plateau. The modified PT-JPL model was calibrated and validated against flux tower-measured and water balance-based ET observations. The model performed well at a regional scale with the incorporation of vegetation dynamics. To quantify the net effect of revegetation on evaporative water consumption after the GfGP, we compared scenarios with and without revegetation. We find the revegetation has led to a significant increase in ET across the Loess Plateau, of 4.39 mm/yr averaged over the past 15 years (mean annual precipitation was 464 mm). Compared with the no revegetation scenario, the GfGP revegetation appreciably enhanced evaporative water consumption across the Loess Plateau, by approximately 31 x 10(8) m(3)/yr (or 4.90 mm/yr). Our findings suggest that to maintain ecologically sustainable restoration and rational use of water resources, factors including the strength of revegetation and the relationship between evaporative water consumption and revegetation type should be considered.