Accurate estimations of evapotranspiration (ET) are essential for understanding land-atmosphere coupling and atmosphere-underlying surface energy and water vapor exchanges. Based on input data processing, this paper simulates the temporal and spatial variation of ET in the Dajiuhu Basin from 1990 to 2018 using the BEPS-TerrainLab V2.0 model. Compared with the ET measured by an eddy covariance (EC) tower, the model explained 80.1% of the ET variation. From 1990 to 2018, the average annual ET in the Dajiuhu Basin was 1262.7 mm/yr indicating a downward trend (−27.12 mm/yr). In 2005, a sudden change point was observed based on the Mann-Kendall (MK) test and 3-year moving t-test. Around 2005, the downward trend in ET slowed and the proportional trend of ET to precipitation changed from upward trend to downward trend. Regarding spatial distribution, the ET in the basin's central part was smaller than that in the basin's surrounding area, the ET of the southern slope was higher than that of the northern slope, and the decrease in the ET rate on the sunny side was lower than that on the shady side. ET decreased as the elevation increased, with the fastest decrease observed between 2184 and 2384 m. For different landcover types, the average ET exhibited the following order: deciduous forest > mixed forest > wetland > grass > agriculture land. Decreased solar radiation is the main reason for the decreased ET in the Dajiuhu Basin, followed by increased wind speed and relative humidity, which together contribute 83.9% to the ET trend. This paper provides a theoretical basis for the study of ET changes and the mechanism of ET and provides a decision-making reference for water resource management in the Dajiuhu Basin and even the South-to-North Water Transfer Project.

中文翻译：

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基于BEPS-TerrainLab V2.0的大九湖盆地1990-2018年蒸散模拟

蒸发蒸腾 (ET) 的准确估计对于理解陆地-大气耦合和大气底层表面能和水汽交换至关重要。本文在输入数据处理的基础上，利用BEPS-TerrainLab V2.0模型模拟了1990—2018年大九湖盆地ET的时空变化。与涡流协方差 (EC) 塔测量的 ET 相比，该模型解释了 80.1% 的 ET 变化。1990—2018年，大九湖盆地年均ET为1262.7 mm/yr，呈下降趋势（-27.12 mm/yr）。2005 年，根据 Mann-Kendall (MK) 检验和 3 年移动 t 检验观察到突变点。2005年前后，ET下降趋势放缓，ET与降水的比例趋势由上升趋势转为下降趋势。关于空间分布，流域中部ET小于流域周边，南坡ET高于北坡，向阳侧ET率下降幅度小于阴坡边。ET 随海拔升高而降低，在 2184 至 2384 m 之间观察到的下降最快。对于不同的土地覆盖类型，平均ET呈现出以下顺序：落叶林>混交林>湿地>草地>农田。太阳辐射减少是大九湖盆地ET减少的主要原因，其次是风速和相对湿度增加，两者对ET趋势的贡献率为83.9%。