물금, 양산천, 화명동 그리고 하단에 이르는 낙동강하류역에서 1983년 5~6월에 조석변동에 따른 수질분석과 유출량을 조사하여 오염부하량을 산출하고, 양산천의 본류에 대한 영향을 평가한 결과는 다음과 같다. 1. 양산천의 총부유물질 값은 6.1~21.3mg/l로 다른 측점에서보다 높았다. BOD의 평균치는 물금에서 1.16mg/l, 양산천 1.83mg/l, 화염동 0.79mg/l, 하단에서 3.56mg/l였다. 2. 영양염류의 농도는 하단에서 가장 높았고, 양산천에서의 값 역시 본류 보다 약간 높게 나타났다. 구리와 아연의 농도는 양산천에서 가장 높았다. 3. 각 측점에서의 평균유출량은 물금 97.02m super(3)/sec 양산천 3.7m super(3)/sec, 화명동에서 98.76m super(3)/sec였고 양산천의 본류에 대한 유출량 비는 약 4% 정도였다. 4. TSS, VSS, BOD에 대한 오염부하량들은 상류인 물금에서 하류인 화명동으로 갈수록 감소하였으나 BOD와 영양염류의 부하량은 화명동에서 높게 나타났다. 5. 물금에서의 평균부하량에 대한 양산천의 평균부하량 비는 약 8.3%로 나타났다.

Electrical Conductivity (EC) or Total Dissolved Solids (TDS) has been often used to evaluate the water quality in some water education program for children and youth. This study attempted to find out whether EC (or TDS) can be used as a water pollution criteria in water education program. To clarify it, we used the water analysis data of July 2019 and January 2020 from Water Environment Information System. Data from 332 points in Han-river were used to investigate correlation between the parameters, such as BOD, COD, TN, TP vs EC. Correlation(r) for all data of BOD vs. EC was 0.347 for July 2019 and 0.483 for January 2020. No correlation was observed for BOD Ia and BOD Ib for July 2019 (r=-0.041, -0.030, respectively) and BOD Ia for January 2020 (r=0.041). Better correlation for all data of COD vs. EC was obtained (r=0.543 for July 2019 and r=0.610 for January 2020). However, no correlation was observed for COD Ia for January 2020. High vlaue of EC or TDS does not always mean water pollution, especially for clean water environment. Thus, EC (or TDS) alone can not be used as a water pollution criteria.

For the development of flow duration curves for the management of 41 Total Maximum Daily Load (TMDL) units of the Nakdong River basin, first, an equation for estimating daily flow rates as well as the level of correlation (correlation and determination coefficients) was extrapolated through regression analysis of discrete (Ministry of Environment) and continuous (Ministry of Land, Infrastructure and Transportation) measurement data. The equation derived from the analysis was used to estimate daily flow rates in order to develop flow duration curves for each TMDL unit. By using the equation, the annual flow duration curves and flow curves, for the entire period and for each TMDL unit of the basin, were developed to be demonstrated in this research. Standard flow rates (abundant-, ordinary-, low- and drought flows) for major flow duration periods were calculated based on the annual flow duration curves. Then, the flow rates, based on percentile ranks of exceedance probabilities (5, 25, 50, 75, and 95%), were calculated according to the flow duration curves for the entire period and are suggested in this research. These results can be used for feasibility assessment of the set values of primary and secondary standard flow rates for each river system, which are derived from complicated models. In addition, they will also be useful for the process of implementing TMDL management, including evaluation of the target level of water purity based on load duration curves.

In recent years, the United States has used the Load Duration Curve (LDC) method to identify water pollution problems, considering the size of the pollutant load in the entire stream flow condition to effectively evaluate Total Maximum Daily Loads (TMDLs). A study on the improvement of the target water quality evaluation method was carried out by comparing evaluations of two consecutive years of water quality and LDC data for 41 unit watersheds (14 main streams and 27 tributaries). As a result, the achievement rate of the target water quality evaluation method, according to current regulations, was 68-93%, and that by the LDC method was 82-93%. Evaluating the target water quality using the LDC method results in a reduction in the administrative burden and the total amount of planning as compared to the current method.

This study evaluated the effect of water level of water resources on water quality in Ulsan. Two reservoirs, Sayeon Dam and Hoeya Dam, were selected and water quality of chemical oxygen demand (COD), total nitrogen (TN) and total phosphorus (TP) were analyzed from 2012 to 2014. And the characteristics of precipitation were also analyzed for 70 years (1945~2014) because runoff of non-point pollutant was strongly affected by precipitation. As a result, water deterioration of Sayeon Dam and Hoeya Dam were affected in accordance with lowering water level. For example, the concentrations of COD and TN was negatively correlated with the water level when the water level of Sayeon Dam was gradually decreased in 2013. The TN concentration was increased to 1.432 mg/L from 0.875 mg/L while the lowest water level of Sayeon Dam was recorded 45 m in 2014. Additionally the concentration of COD and TN was sensitively increased with 0.213 mg/L/m and 0.058 mg/L/m on account of non-point pollutant runoff. It is indicated that hereafter a control of non-point pollutant runoff is the critical factors to maintain water resources because the contribution of non-point pollutant is expected to increase due to the frequent heavy rain events. Therefore, it is necessary to map out a specific plan for non-point pollutant control based on analyses of runoff characteristics, water pollution sources and reduction plans in water pollutants and to establish a water modelling and database system as a preventive action plan.