Unraveling human influence on evapotranspiration over East Asian monsoon river basins by using GRACE/GRACE-FO data and land surface models

Abstract

With intensified human influences on the terrestrial water cycle, evapotranspiration (ET) is changed even at a large river basin scale. However, there is no consensus about the significance of the human-induced ET change across river basins due to the uncertainties from the estimations of both observed and natural ET at a large scale. In this study, the human influence on ET is estimated over seven large river basins in the East Asian monsoon region during 2003–2019, where the actual ET estimations based on the water budget method using the Gravity Recovery and Climate Experiment (GRACE) and GRACE Follow-On terrestrial water storage change and the natural ET estimations based on land surface modeling are compared. The state-of-the-art global reanalyses and the Variable Infiltration Capacity (VIC) land surface model are validated against naturalized runoff from the water resources bulletins, and the VIC model is found to outperform global reanalysis data over most southern river basins. Compared with the selected natural ET model data that has a good performance of naturalized runoff, the annual mean human-induced ET in the East Asian monsoon region is estimated to range from 38 ± 28 to 100 ± 76 mm/year (8 ± 6% to 12 ± 9% of the total ET) during 2003–2019. The reservoir evaporation contributes to 5–18% of the human-induced ET change especially over the Huai river basin. Our results reveal that human-induced ET change is more significant over northern semiarid basins than southern humid basins.