In this study, a load duration curve was applied to the Jangseongcheon, one of the tributaries of the Yeongsan River, to assess whether the target water quality was achieved. In addition, pollution of the water body was investigated to develop and suggest the optimal management time with respect to polluted flow sections and monthly conditions. The average flow rates of sections JS1 and JS2 were 0.25 m3/s and 1.08 m3/s , respectively. The BOD and T-P for water-quality standards at JS1 were rated at II, whereas the COD and TOC were rated at III, thus indicating a fair level of water quality. By contrast, the BOD at JS2 was rated at III, the T-P at IV, and the TOC at V, indicating poor water quality in this section. The load duration curve was plotted using the actual flow data measured in eight-day intervals for eight years from 2011 to 2018 at locations JS1 and JS2 in the Jangsungcheon Basin. In an assessment using the load duration curve on whether the target water quality was met at location JS1, all of the water quality parameters (BOD, COD, TOC, T-N, T-P, and SS) satisfied the target water quality. By contrast, at location JS2, parameters COD, TOC, T-N, and T-P exceeded target values by more than 50%, indicating the target water quality was not met. The discharge loads of locations JS1 and JS2 were analyzed to identify the reasons the target water quality was exceeded. Results revealed that the land system contributed considerably. Furthermore, the discharge load of JS2 accounted for more than 80% of the load on the entire basin, excluding that of JS1. Therefore, the best method for restraining the inflow of pollutants into the stream near location JS2 must be applied to manage the water quality of the Jangsungcheon.

Abstract
1. Introduction
2. Materials and methods
    2.1. Study area
    2.2. Methods for measuring water quality and flowrate
    2.3. Load duration curve method
    2.4. Investigation of pollutant sources
3. Results and discussion
    3.1. Analysis of runoff characteristics for measuringpoints using the flow duration curve
    3.2. Analysis of the water quality change in thewatersheds
4. Conclusions
REFERENCES

• Sohyun Cho(Yeongsan River Environment Research Center, National Institute of Environmental Research)
• Jonghun Bak(Yeongsan River Environment Research Center, National Institute of Environmental Research)
• Yeong Jae Lee(Yeongsan River Environment Research Center, National Institute of Environmental Research)
• Kyunghyun Kim(Yeongsan River Environment Research Center, National Institute of Environmental Research)
• Kang Young Jung(Yeongsan River Environment Research Center, National Institute of Environmental Research) Corresponding author