## 3 Results and Discussions
### Derivation of LDC for Each Point
\begin{tabular}{c} **Water Quality** \\ **Factor** \\ \end{tabular}  & **High Flows** & \begin{tabular}{c} **Moist** \\ **Conditions** \\ \end{tabular}  & \begin{tabular}{c} **Mid-Range** \\ **Flows** \\ \end{tabular}  & \begin{tabular}{c} **Dry** \\ **Conditions** \\ \end{tabular}  & **Low Flows** \\ \hline \multirow{4}{*}{ \begin{tabular}{c} Phase 1 \\ Target Water \\ Overage Rate \\ \end{tabular}  } & Upper & \ \begin{tabular}{c} BOD \\ T-P \\ BOD \\ T-P \\ BOD \\ T-P \\ BOD \\ T-P \\ BOD \\ T-P \\ BOD \\ T-P \\ \end{tabular}  &
\begin{tabular}{c} 0 \\ 0 \\ 55.56 \\ 5.26 \\ 5.26 \\ 5.26 \\ 5.26 \\ 5.26 \\ 5.  
used as nutrients for crops. This can also explain the increase in the BOD concentration in the lower part of the Gul-po stream during rainfall, due to the high proportions of paddy fields. In addition, the presence of phosphorus can be explained by the inflow of soil with a large amount of phosphorus adsorbed along with the rainfall runoff, because phosphorus has a high soil adsorption capacity [31]. Therefore, in the lower part of the stream, where there is a high proportion of farmland, it was ascertained that the related pollutant load (BOD, T-N) is introduced into the stream, along with rainfall, and affects the water quality. When the target water quality overage rates in phase 2 were compared for each point, it was found that the overage rate increased for all flow sections in the upper, middle, and lower parts. In the case of BOD, in particular, the overage rate was higher than 50% for all flow sections in the middle part and thus could not satisfy the target water quality. This indicates that the water quality management plan must be improved, considering both point and nonpoint pollution sources. Intensive management is required for the DC and LF sections in the upper part that exhibited overage rates of 46.5% and 60%, and the HF section in the lower part that showed an overage rate of 47.37%. As shown in Figure 4 and Table 4, it was found that the target water quality was satisfied in the upper part, since the overage rate was less than 50% for all flow sections. For both BOD and T-P, however, the overage rates for low-flow sections, i.e., normal conditions, were higher than those for high-flow sections, indicating that point pollution sources had a larger influence on the occurrence of water pollution than nonpoint pollution sources. In the middle part, BOD did not satisfy the target water quality for high flows (HFs); this appears to be due to the influence of nonpoint pollution sources and the inflow of the Sam-jeong stream (a tributary) during rainfall in nearby areas. It is suggested that the increase in suspended matter due to the inflow of nearby pollution sources is the cause for the increase in the concentrations of BOD and organic matter. In the lower part of the stream, the target water quality was also satisfied, since the overage rate was less than 50% for all flow sections. Since both BOD and T-P exhibited high overage rates for high-flow sections, however, it is suggested that the nonpoint pollution sources had a significant influence on the occurrence of water pollution when the results of the flow-pollutant loading equation are also considered. In particular, BOD exhibited higher overage rates than T-P. This appears to be due to the high proportions of paddies and fields in the lower part in terms of land use.