Agriculture is a major consumptive user of water through evapotranspiration (ET). Quantification of actual ET (ET_a) is of significant interest to better address water management and improve decision making in the agricultural sector. Many methods to estimate ET are available. However, due to the increasing need of validation of estimates of ET from various techniques, there arises a call for a critical comparison of ET_a estimated from a combination of methods. This research presents a critical comparison of ET_a estimates obtained using ground based (eddy covariance), remotely sensed (ET ensemble), and simulated data (a crop-soil-water balance model, SIMETAW#). The study focuses on experimental sites in Nebraska, Oklahoma and California (USA). Results show a relatively small and consistent variation between the three methods. The results are relatively close giving a reasonable impression of the expected ET_a at a site including variability which is useful to address agricultural practices. The estimates from remote sensing deviate from the other two methods since the method used is relatively new and requires further research to improve measurements and ET estimation. This study offers water managers at the sites new information for reliable, multi-source ET estimation for water resources planning and the study is in principle replicable at different locations.

农业是通过蒸散（ET）消耗水的主要使用者。为了更好地解决水资源管理问题并改善农业部门的决策，对实际ET（ET _a）进行量化非常重要。估计ET的方法很多。然而，由于越来越需要从各种技术ET的估计验证，出现了ET的一个比较关键的调用_一个从相结合的方法来估计。这项研究提出了ET _a的关键比较使用基于地面的（涡动协方差），遥感的（ET系综）和模拟数据（作物-土壤-水平衡模型，SIMETAW＃）获得的估算值。该研究的重点是内布拉斯加州，俄克拉荷马州和加利福尼亚州（美国）的实验点。结果显示这三种方法之间的变化相对较小且一致。结果相对接近，给人对预期ET_的合理印象在包括变异性的地点，这对解决农业实践很有用。由于使用的方法是相对较新的方法，因此遥感估算与其他两种方法有所不同，需要进一步研究以改进测量和ET估算。这项研究为现场的水资源管理者提供了新的信息，以进行可靠，多源的ET估算，以进行水资源规划，并且该研究原则上可以在不同的地方进行复制。