# Evaluation of Remote Sensing-Based Evapotranspiration
## 4 Results and Discussion
### Multi-Variable Calibration (Scheme II)  
#### 4.3.1 Performance Analysis at Different Temporal Resolutions  
All three multi-variable calibrations (namely Scheme II (PML), Scheme II (FLUXCOM), and Scheme II (GLEAM)) are applied in this section for parameter calibration. Both the KGE and PBIAS of runoff and ET are utilized as objective functions. To investigate the utility of the three remote sensing-based ET datasets in improving hydrological model simulation (runoff and ET simulations), the hydrological model performance at different temporal resolutions is analyzed. Regarding the daily temporal resolution, Table 4 presents the evaluation indices of runoff and ET simulations. As shown in Table 4, the performance of runoff simulations based on all three variants of Scheme II is comparable with that based on Scheme I. The KGE values of the runoff simulations based on all three variants of Scheme II are above 0.72 in the calibration period and above 0.85 in the validation period. Furthermore, the value of KGE reaches up to 0.91 in the validation period under Scheme II, and the value is higher than that under Scheme I. In addition, compared to Scheme I, the PBIAS in the validation period for all three Scheme II variants is slightly reduced, but not for the calibration period. A similar situation occurs for ME. The R values under Scheme II are almost the same as that under Scheme I. For RMSE, the values based on Scheme II are slightly increased, but  
Figure 5: Comparison of observed and simulated daily runoff in the calibration (2004) and validation periods (2009) based on Scheme I.  
they are still acceptable. For the three ET datasets, the runoff simulation based on Scheme II (PML) has the highest KGE and lowest PBIAS in the calibration period, which are 0.87 and 1.46%, followed by those based on Scheme II (GLEAM) (KGE = 0.75, PBIAS = 9.34%) and Scheme II (FLUXCOM) (KGE = 0.72, PBIAS = 11.82%). Moreover, the RMSE and ME values of the runoff simulation based on Scheme II (PML) are the lowest in the calibration period (RMSE = 74.72, ME = 1.56), followed by those based on Scheme II (GLEAM) (RMSE = 76.10, ME = \(-\)9.98) and Scheme II (FLUXCOM) (RMSE = 75.16, ME = \(-\)12.62). The relative performance of runoff and ET simulations from all three variants of Scheme II to those from Scheme I are also calculated. The evaluation indices of the ET simulation from Scheme I are based on GLEAM, because of its better accuracy, as stated in Section 4.1. ET simulations from all three variants of Scheme II are greatly improved. The KGE and R values of the ET simulations based on all three variants of Scheme II are increased by up to 45.55% and 35.47% in the calibration period, respectively. The values of PBIAS, RMSE, and ME are decreased by up to 95.85%, 50.97%, and 96.72% in the calibration period, respectively. ET simulations in the validation period show similar performance to those in the calibration period. Figure 6 shows a temporal comparison of the simulated and observed daily runoff for the calibration (2004) and validation (2009) periods. The figure shows that the DHSVM model calibrated by all three variants of Scheme II can generate reliable runoff simulations. Compared to Scheme I, peak flow simulation based on all three Scheme II variants is greatly improved in the calibration and validation periods. For instance, the observed peak flow is 823 m\({}^{3}\)/s in June 2009, and the model-generated simulated peak flows are 570 m\({}^{3}\)/s, 585 m\({}^{3}\)/s, and 595 m\({}^{3}\)/s under Scheme II (PML), Scheme II (FLUXCOM), and Scheme II (GLEAM), respectively, while the model under Scheme I generates a simulated peak flow of 468 m\({}^{3}\)/s. Furthermore, for the peak flow in August 2009, the observation is 965 m\({}^{3}\)/s; for the model under Scheme I, the simulated peak flow is 643 m\({}^{3}\)/s, while, for the model under Scheme II, the simulated peak flows are 779 m\({}^{3}\)/s, 821 m\({}^{3}\)/s, and 849 m\({}^{3}\)/s for PML, FLUXCOM, and GLEAM, respectively.