## 3 Results
### Reservoir Simulation Result
#### 3.2.2 Zone B Simulation Results  
In the case of Zone B, unlike Zone A, the average measured water quality (0.101 mg/L) slightly exceeded the target water quality (0.1 mg/L). Figure 11 shows the simulation results of the T-P water quality changes in the reservoir from 2015 for the corresponding scenarios with regard to Zone B. The annual average T-P concentration of the water quality was 0.101 mg/L when no measure was applied, whereas the concentrations for S1, S2, S3, and S4 were 0.089 mg/L, 0.086 mg/L, 0.090 mg/L, and 0.086 mg/L, respectively. In the case of Zone A, as the flow is not smooth owing to the narrow waterway resulting from the high soil pollution level and benthic flux, the downstream water quality is improved owing to the influence of Zone A water quality in the case of dredging (Zone A). Regarding the change tendency of the overall water quality, similar to Zone A, the slope is gradual when no measure is applied during the water quality improvement process after deterioration. This implies the water quality resilience of the estuarine reservoir is low when the load is high. Therefore, even though it is difficult to achieve the water quality goal of an estuarine reservoir merely by dredging, it can enhance the resilience of estuarine reservoir systems.  
In particular, Scenarios 1-4 show similar results, which implies Zone B has a lower soil pollution level than Zone A and is unlikely to be influenced even with dredging, while the elution speed is not fast. In addition, as Zone B shares a large reservoir area with Zone C, dredging does not have a considerable impact. Thus, when comprehensively comparing with the results of Zone A, dredging in Zone B has an insignificant influence on water quality improvement and increases upstream resilience. Particularly, as it does not have a major influence on the downstream water quality, the water quality improvement from dredging is not significant.  
A comparison of the annual average T-P water quality concentration (Figure 12) shows that the water quality concentrations in Scenarios 5 and 6 were 0.094 mg/L and 0.089 mg/L, respectively. The dredging scenario results (S1-S4) of Zone B are better than those of Scenarios 5 and 6, unlike in Zone A. As stated previously, even if the inflow load in the upstream is reduced when the flow is not smooth owing to the embankment located in the middle, the influence on the downstream appears to be insignificant. In other words, when compared with Zone A, Zones B and C are less influenced by the contaminant delivery ratio of the load from the PSTWs. In addition, as reservoir dredging is a method to enhance internal resilience, it is important to prioritize the removal of high concentrations of contaminated soil for overall water quality improvement.  
Figure 11: Simulated results of T-P concentration (Zone B, S0, S1–S4).  
Finally, Figure 13 shows the results of the combined scenarios. The annual average T-P concentrations of Scenarios 7 and 8 are found to be 0.08 and 0.074, respectively. The results show that the water quality concentration was recovered considerably owing to the effect of water quality improvement in Zone A.