Variations in actual evapotranspiration and their influence on the seasonal drought in China's Southeastern River basin

Abstract Revealing changes in actual evapotranspiration and their influencing factors is essential to understand regional extreme hydrological events (e.g., droughts). This study utilized the Global Land Evaporation Amsterdam Model (GLEAM) to analyze the spatial and temporal characteristics of actual evapotranspiration over a 40-year period in the Southeast River basin of China. Then it quantified the relationship between changes in actual evapotranspiration and the drought index. Results indicated a significant increase in actual evapotranspiration in the Southeast River basin over the past 40 years (2.51 mm/yr, p < 0.01). From the perspective of actual evapotranspiration components, it was dominated by vegetation transpiration (73.45%) and canopy interception (18.26%). The actual evapotranspiration was closely related to the NDVI (r = 0.78, p < 0.01), and vegetation changes could explain 10.66% of the increase of actual evapotranspiration in the Southeast River basin since 2000. Meanwhile, actual evapotranspiration and SPEI index showed a highly significant negative spatial correlation with a Moran's I index of -0.513. The rise in actual evapotranspiration is an important reason for the frequent seasonal droughts in the region, for example, in 2003 and 2011. Therefore, these results help deepen the understanding of hydro-climatic process changes in the southeast coastal area of China.