Actual evapotranspiration (ETa) is a central process in the climate system and a nexus of the water and energy cycles. This study assesses the hydrological performance of the four categories of ETa products (i.e., land surface models (LSMs), reanalysis, model tree ensemble, and diagnostic models (DMs)) for use in the middle Yellow River Basin (MYRB) using water balance methods. The results show the following. (1) The water storage changes significantly at annual scale and cannot be neglected when calculating the reference ETa by the water balance methods. (2) ETa from LSMs, considering the precipitation input, exhibits the best performance in capturing the reference ETa variation. The MET ETa (AETJUNG), based on eddy covariance, has fair performance with a small underestimation, followed by the DMs, including MODIS and ZhangKe. Poor performance is found in reanalysis ETa (JRA55), due to overestimations precipitation and radiation. (3) The reference ETa showed decreased and then increased trend. ETa from the LSMs-Noah model captures the trend well, followed by the LSMs-variable infiltration capacity model. Our results are not only meaningful for better understanding ETa variability in the MYRB, but also significant for improving global ETa products models' performance in semi-arid and semi-humid regions.

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