## 3 Results
### Simulation Results of the Daily FTOP Model  
The NSGA-II algorithm was used to optimize the parameters of the daily scale FTOP model, and the best parameters obtained are shown in Table 2. Table 3 describes the simulation effects of the three TOPMODEL models in different periods. In the calibration period, the NSE of the FTOP model and NTOP model were 0.84 and 0.85, respectively, which were more significant than that of the ITOP model (0.80). The REs of the FTOP and ITOP model were \(-\)0.25% and \(-\)3.50%, respectively, much better than the \(-\)18.60% of the NTOP model. The performances of the FTOP model, NTOP model, and ITOP model were similar in RMSE, being 12.60 m\({}^{3}\)/s, 12.25 m\({}^{3}\)/s, and 13.78 m\({}^{3}\)/s, respectively. In the validation period, the NSEs of the FTOP model and ITOP model were 0.81 and 0.84, respectively, much better than that of the NTOP model (0.72). The REs of the FTOP and ITOP models were \(-\)37.68% and \(-\)40.01%, respectively, slightly better than the \(-\)43.99% of the NTOP model. Similarly, the FTOP, NTOP, and ITOP models showed little difference in RMSE performance. In the whole simulation period, the FTOP model was undoubtedly the best. The NSE, RE, and RMSE of the FTOP model were 0.82, \(-\)11.14%, and 15.25 m\({}^{3}\)/s, respectively, being better than those of the NTOP and ITOP models. Figure 4 compares the simulated flow and the observed flow of the FTOP model, NTOP model, and ITOP model. It can be seen from Figure 4 that the simulated flow curve of the FTOP model fit well with the observed flow curve. Especially in low annual flow, the advantages of the FTOP model were more prominent. At the same time, we can also see that the performance of the NTOP model was the worst among the three TOPMODEL models. Figure 5 illustrates the scatter plots of observed flow and simulated flow of the FTOP model, NTOP model, and ITOP model. When the scatter shown in Figure 5 was closer to the diagonal (that is, the dotted line in Figure 5), it indicated that the simulation was preferable and vice versa. Compared with the NTOP model and ITOP model, it can be seen that the scatter points of the FTOP model were uniformly distributed on both sides of the diagonal, which indicated that the simulation effect of the FTOP model was better than that of the NTOP model and ITOP model. \begin{table}
\begin{tabular}{c c c} \hline
**Parameter** & **Value** & **Unit** \\ \hline \(T_{0}\) & 2.06 & m\({}^{2}\)/d \\ \(S_{zm}\) & 0.02 & m \\ \(S_{tmax}\) & 0.96 & m \\ \(S_{ro}\) & 0.10 & m \\ \(td\) & 3.17 & d \\ \(k\) & 6.28 & / \\ \(n\) & 2.17 & / \\ \(\alpha\) & 0.35 & / \\ \hline \end{tabular}
\end{table} 
Table 2: Parameter values of the daily FTOP model. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline  & \multicolumn{3}{c}{**NSE**} & \multicolumn{3}{c}{**RE**} & \multicolumn{3}{c}{**RMSE**} \\ \cline{2-10}  & **FTOP** & **NTOP** & **ITOP** & **FTOP** & **NTOP** & **ITOP** & **ITOP** & **NTOP** & **ITOP** \\ \hline Calibration period & \multirow{2}{*}{0.84} & \multirow{2}{*}{0.85} & \multirow{2}{*}{0.80} & \multirow{2}{*}{\(-\)0.25\%} & \multirow{2}{*}{\(-\)18.60\%} & \multirow{2}{*}{\(-\)3.50\%} & \multirow{2}{*}{12.60} & \multirow{2}{*}{12.25} & \multirow{2}{*}{13.78} \\ (1989–1994) & & & & & & & & \\ \hline Validation period & \multirow{2}{*}{0.81} & \multirow{2}{*}{0.72} & \multirow{2}{*}{0.84} & \multirow{2}{*}{\(-\)37.68\%} & \multirow{2}{*}{\(-\)43.99\%} & \multirow{2}{*}{\(-\)40.01\%} & \multirow{2}{*}{21.29} & \multirow{2}{*}{25.72} & \multirow{2}{*}{19.26} \\ (1995–1996) & & & & & & & & \\ \hline Simulation period & \multirow{2}{*}{0.82} & \multirow{2}{*}{0.79} & \multirow{2}{*}{0.82} & \multirow{2}{*}{\(-\)11.14\%} & \multirow{2}{*}{\(-\)25.98\%} & \multirow{2}{*}{\(-\)14.11\%} & \multirow{2}{*}{15.25} & \multirow{2}{*}{16.67} & \multirow{2}{*}{15.34} \\ (1989–1996) & & & & & & & & \\ \hline \end{tabular}
\end{table} 
Table 3: Statistical index comparison table of three TOPMODEL models.