Description:
<p>Studies are underway to improve the water qualities by introducing riparian buffers to existing rivers to manage non-point sources (NPSs) pollution, but they were not applied to prevent the inflow of land-based NPSs to coastal regions. Herein, we introduced methodological approach to the application of riparian buffer zones for mitigating NPSs at coastal regions, reflected by river-based simulation. We used hydrological simulation program–FORTRAN (HSPF) for the watershed of Unmun Dam, Korea, which can simulate the watershed hydrology with water quality for NPSs contaminated runoff including the fate and transport of pollutants in stream channels. We applied a riparian buffer to the prepared watershed, which is one of the best management practices, to estimate the reduction efficiency of NPSs according to the size of buffer zone. The model was calibrated and validated using four year records (2012-2015) in various scenario series. We obtained that decision coefficients (R²) were very good level for the flow rate and water quality, but biological oxygen demand (BOD), total nitrogen (TN), and total phosphate (TP) were generally not good. Instead, %difference was evaluated as very good level. Five scenarios (five different zone size of riparian buffer zone: 0.1 ha, 0.2 ha, 0.4 ha, 0.8ha, 1.6 ha) were investigated to determine its optimized zone size at the one site in the Unmun Dam Watershed. In Scenario 5 (1.6 ha), the efficiency reduction of TP was 82.329% when there was more than 30 mm of rainfall. However, simulation results showed lower efficiency of TN than expected, which illustrates that this result does not reflect the watershed’s characteristics well. The efficiency of the reduction of NPSs pollution was greatly increased in Scenario 4 (0.8 ha). It is considered that the construction of more than 0.8 ha of riparian buffer in the watershed of Unmun Dam would be effective in reducing the NPSs pollution (BOD: >32.52%, TN: >20.68%), TP: >61.34%).</p>