## 3 Results
### Streamflow Calibration and Uncertainty  
The analysis of the results showed that the SWAT model is suitable for flow evaluation in the Lobo watershed at Nibehibe. Indeed, R\({}^{2}\), NSE, and PBIAS had values of 0.63, 0.62, and \(-8.1\), respectively. The values of P_factor and R_factor were 0.48 and 0.52 (Table 4).  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Global** & & & & & \\
**Sensitivity** & **Parameter** & **Description** & **Fitted** & **Minimum** & **Maximum** \\
**Rank** & & & & & \\ \hline
1 & v\_GW\_REVAP &
\begin{tabular}{c} Groundwater \\ evaporation \\ coefficient \\ \end{tabular} & 0.1649 & 0.02 & 0.2 \\ \hline
2 & a\_GWQMN &
\begin{tabular}{c} Threshold depth of \\ water in the \\ shallow aquifer \\ required for return \\ flow to occur (mm) \\ \end{tabular} & \(-162\) & \(-1000\) & \(1000\) \\ \hline
3 & a\_RCHRG\_DP &
\begin{tabular}{c} Deep aquifer \\ percolation \\ fraction \\ \end{tabular} & \(-0.0205\) & \(-0.05\) & \(0.05\) \\ \hline
4 & v\_ESCO &
\begin{tabular}{c} Soil evaporation \\ compensation factor \\ \end{tabular} & 0.5465 & 0.5 & 0.8 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Summary of selected SWAT parameters’ global sensitivity and parameters’ fitted values for simulating streamflow.  
The graph in Figure 5 shows the results of the water flow calibration. SWAT model predictions generally follow the trend of observed flow. However, we note a shift in the flow peaks at the end of the simulation period (1981-1994).  
From 1 January 1981 to 1 January 1990, the model has globally reproduced the observed flow correctly. However, from 1 January 1990 to 31 December 1994, the opposite is observed. Indeed, the SWAT model could not reproduce the peak flows and overestimated the base flow.  
The uncertainties in the predictions are highlighted by P-factor and R-factor. The P-factor and R-factor values obtained were 0.48 and 0.52, respectively. This situation is explained by the fact that the SWAT model could not faithfully restore the peakflow from 1 January 1983 to 1 January 1985.  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Statistic Coefficients** & **Value** \\ \hline R\({}^{2}\) & 0.63 \\ NSE & 0.62 \\ PBIAS & \(-8.1\) \\ P\_factor & 0.48 \\ R\_factor & 0.52 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Summary statistics.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Global** & & & & & \\
**Sensitivity** & **Parameter** & **Description** & **Fitted** & **Minimum** & **Maximum** \\
**Rank** & & **SCS runoff curve** & & & & \\ \hline
5 & r\_CN2 &
\begin{tabular}{c} SCS runoff curve \\ number function \\ \end{tabular} & 0.081 & \(-0.1\) & 0.1 \\ \hline
6 & a\_GW\_DELAY &
\begin{tabular}{c} Groundwater delay \\ (days) \\ \end{tabular} & \(-28.83\) & \(-30\) & 60 \\ \hline
7 & a\_REVAPMN &
\begin{tabular}{c} Threshold depth of \\ water in the shallow \\ aquifer for “rexp” to \\ occur (mm) \\ \end{tabular} & 370.50 & \(-750\) & 750 \\ \hline
8 & v\_ALPHA\_BF &
\begin{tabular}{c} Baseflow alpha factor \\ (days) \\ \end{tabular} & 0.945 & 0.00 & 1.00 \\ \hline
9 & r\_SOL\_AWC &
\begin{tabular}{c} Available water \\ capacity of the soil \\ layer \\ \end{tabular} & \(-0.0143\) & \(-0.05\) & 0.05 \\ \hline
10 & v\_CANMX &
\begin{tabular}{c} Maximum canopy \\ storage \\ \end{tabular} & 14.1749 & 0.00 & 15.00 \\ \hline \hline \end{tabular} a: Add parameter value to an existing value; v: Replace the given value with another; r: Multiply the existing parameter value by (1 + a given value of the same parameter).  
\end{table}
Table 3: Summary of selected SWAT parameters’ global sensitivity and parameters’ fitted values for simulating streamflow (continued from Table 2).