• Magazine of the Korean Society of Agricultural Engineers
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• v.45 no.4
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• pp.78-88
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• 2003

The land use changes from non-urban areas to urban areas lead to the increased impervious areas, consequently increased direct runoff and higher peak runoff. Urban areas have also been recognized as significant sources of Nonpoint Source (NPS) pollution, while agricultural activities have been known as the primary sources of NPS pollution. Many features of the L-THIA/NPS GIS, L-THIA/NPS WWW system have been enhanced to provide easy-to-use system. The L-THIA model was applied to the Little Eagle Creek (LEC) watershed in Indiana to evaluate the accuracy of the model. The L-THIA/NPS GIS estimated yearly direct runoff values match the direct runoff separated from U.S. Geological Survey stream flow data reasonably. The $R^2$ and Nash-Sutcliffe values are 0.67 and 0.60, respectively. The L-THIA estimated runoff volume and total nitrogen loading for each land use classification in the LEC watershed were computed. The estimated runoff volume and total nitrogen loading in the LEC watershed increased by 180% and 270% for the 20 years. Urbanized areas -"Commercial", "High Density Residential", and "Low Density Residential"- of the LEC watershed made up around 68% of the 1991 total land areas, however contributed more than 92% of average annual runoff and 86% of total nitrogen loading. Therefore, it is essential to consider the impacts of land use change on hydrology and water quality in land use planning of urbanizing watershed.nning of urbanizing watershed.

• Journal of Wetlands Research
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• v.11 no.2
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• pp.55-66
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• 2009

The increase of pollutant loadings from nonpoint sources affect the water quality of the major rivers in Korea. Consequently, the need for managing the nonpoint source (NPS) pollution becomes the main concern of the Korean Ministry of Environment (MOE). Recently, the policy was changed from pollutant concentration-restricting approach to the total maximum daily load (TMDL) approach to improve the water quality and protect the aquatic ecosystem. Part of the program is the construction of Best Management Practice (BMP) pilot facilities basically to control NPS. Most of the BMPs adopted were foreign technologies which could not be properly employed in the country due to some limitations such as climate, watershed characteristics, etc. In other words, to be able to apply the BMPs, research on its applicability is necessary. In this study, a three-year monitoring has been conducted to assess the treatment performance of the BMP installed in highway toll plaza and parking lot. The data gathered aid in the characterization of NPS pollutants in runoff and estimation of the pollutant removal efficiency of the BMP. The results will be used for the future implementation of BMP in different land uses as well as for the determination of optimum operation and maintenance.

• Journal of Korean Society on Water Environment
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• v.31 no.2
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• pp.166-180
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• 2015

Pollutant in watersheds comes from two major sources which are NPS (nonpoint source pollution) and PS (point source pollution). Most of the pollutant can be treated by wastewater treatment plants. However, wastewater treatment plants may not be an appropriate practice to improve water quality for the watersheds with large portion of NPS pollutant and NPS pollution from direct runoff and baseflow has different characteristics. Therefore the practices to improve water quality need to be comprehensive for pollutants by both direct runoff and baseflow. Riparian buffer, one of practices to manage pollutant in watershed, has been applied to reduce pollutant not only from direct runoff but also baseflow. In this study, the scenarios for pollutant reduction by wastewater treat plants and the nitrogen reduction by riparian buffer were simulated using SWAT-REMM to suggest an effective plan for pollutant reduction from baseflow. Riparian buffer provided nitrogen reduction of 0.2~75.0% in YbB watershed and 38.0~47.0% in GbA watershed. The result indicates that riparian buffer is effective to reduce the pollutant especially from baseflow, and it suggested as suitable for the a watershed which WWTP discharge is not capable to reduce enough pollutant.

• Journal of Korean Society on Water Environment
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• v.28 no.2
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• pp.255-268
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• 2012

Nonpoint source pollution has become a concern for water quality in the Han River system, especially during the high runoff events during the monsoon season. The patterns in nonpoint source runoff the relationships with land use, rainfall intensity, and stream nutrients concentrations were surveyed in 19 streams in the Han River watershed. The results show that the magnitude of NPS inputs of nutrients and sediment in the Han River watershed are of a serious concern. In the South Han River watershed, event mean concentrations (EMC) for biochemical oxygen demand (BOD), suspended sediment (SS), dissolved organic carbon (DOC), dissolved total phosphorus (DTP), total nitrogen (TN) Nitrate ($NO_3$-N) and total phosphorus (TP) were $1.94mg{\cdot}L^{-1},\;251mg{\cdot}L^{-1},\;2.75mg{\cdot}L^{-1},\;0.076mg{\cdot}L^{-1},\;2.82mg{\cdot}L^{-1},\;2.40mg{\cdot}L^{-1}$ and $0.232mg{\cdot}L^{-1}$, respectively. In the North Han River watershed, EMCs for BOD, SS, DOC, DTP, TN, $NO_3$-N and TP were $1.34mg{\cdot}L^{-1},\;172mg{\cdot}L^{-1},\;2.63mg{\cdot}L^{-1},\;0.032mg{\cdot}L^{-1},\;1.97mg{\cdot}L^{-1},\;1.55mg{\cdot}L^{-1}$ and $0.148mg{\cdot}L^{-1}$, respectively. The specific export coefficients of nutrient and sediments were much higher than those of other reports. Our study also found that the proportion of agricultural field area was significantly correlated with the EMCs for nutrients. Therefore, efforts to reduce NPS loading must focus on agricultural practices in the watershed. The relationships between land use and nutrient and sediment export found in this study can be used to derive estimates of runoff coefficients for agricultural field and as input data for modeling works and to develop total maximum daily load and best management practices in the Han River watershed.

• Korean Journal of Ecology and Environment
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• v.39 no.4 s.118
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• pp.481-488
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• 2006

The field scale experiment was performed to examine the performance of the constructed wetland for nonpoint source (NPS) pollution loading reduction. Four sets (0.88 ha each) of wetland and pond system were used. After three growing seasons of the wetland construction, plant coverage increased to about 90% even without plantation from bare soil surfaces at the initial stage. During the start up period of constructed wetlands, lower water levels should be maintained to avoid flooding newly plants, if wetland plants are to start from germinating seeds. The average removal rate of $BOD_5$, TSS, T-N and T-P during the first two years was 5.6%, 46.6%, 45.7%, and 54.8%, respectively. The $BOD_5$ removal rate was low and it might be attributed to the low influent concentration. The early stage of wetland performance demonstrated the effectiveness of water quality improvement and was satisfactory for treating polluted stream waters. From the first-order analysis, T-P was virtually not temperature dependent, and $BOD_5$ and TSS were more temperature dependent than T-N. A pond-wetland system was more effective than a wetland-pond or a wetland alone system in water quality improvement, particularly to reduce T-P. Overall, the wetland system was found to be an adequate alternative for treating a polluted stream water with stable removal efficiency and recommended as a NPS control measures.

• Journal of The Korean Society of Agricultural Engineers
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• v.50 no.2
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• pp.65-71
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• 2008

A monsoon season monitoring data from June to September, 2005 of a small forested watershed located at the upstream of the North Han River system in Korea was conducted to analyze the flow variations, the NPS pollutant concentrations, and the pollution load characteristics with respect to sampling frequencies. During the 4-month period, 1,423 mm or 79.2% of annual rainfall(1,797 mm) were occurred and more than 77%, 54% and 68% of annual T-N, $NO_3$-N and T-P loads discharged. Flow rate was continuously measured with automatic velocity and water level meters and 58 water quality samples were taken and analyzed. It was analyzed that the flow volume by random measurement varied very widely and ranged from 79% to 218% of that of continuous measurement. It was recommended that flow measurement of small forested watersheds should be continuously measured with automated flow meters to precisely measure flow rates. Flow-weighted mean concentrations of T-N, $NO_3$-N and T-P during the period were 2.114 mg/L, 0.836 mg/L, and 0.136 mg/L, respectively. T-N, $NO_3$-N and T-P loads were sensitive to the number of samples. And it was analyzed that in order to measure the pollution load within the error of 10% to the true load, the rate of sampling frequency should be higher than 89.7% of the sample numbers that were required to compute the true pollution load. If it is compared to selected foreign research results, about 10 water samples for each rainfall event were needed to compute the pollution load within 10% error. It is unlikely in Korea and recommended that thorough NPS pollution monitoring studies are required to develop the standard monitoring procedures for reliable NPS pollution quantification.

• Journal of Korean Society on Water Environment
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• v.39 no.4
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• pp.316-328
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• 2023

In this study, the characteristics of nonpoint pollutant outflow and contribution rate of pollution in Songya-stream mainstream and tributaries were analyzed. Further, water pollution management and improvement measures for pollution-oriented rivers were proposed. An on-site investigation was conducted to determine the inflow of major pollutants into the basin, and it was found that pollutants generated from agricultural land and livestock facilities flowed into the river, resulting in a high concentration of turbid water. Based on the analysis results of the pollution load data calculated through actual measurement monitoring (flow and water quality) and the occurrence and emission load data calculated using the national pollution source survey data, the S3 and S6 were selected as the concerned pollution tributaries in the Songya-stream basin. Results of cluster analysis using Pearson correlation coefficient evaluation and Density based spatial clustering of applications with noise (DBSCAN) technique showed that the S3 and S6 were most consistent with the C2 cluster (a cluster of Songya-stream mainstream owned area) corresponding to the mainstream of Songya-stream. The analysis results of the major pollutants in the concerned pollution tributaries showed that livestock and land pollutants were the major pollutants. Consequently, optimal management techniques such as fertilizer management, water gate management in paddy, vegetated filter strip and livestock manure public treatment were proposed to reduce livestock and land pollutants.

• Journal of The Korean Society of Agricultural Engineers
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• v.56 no.5
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• pp.21-27
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• 2014

Sediment-laden water is problematic in aquatic ecosystem and for hydraulic structures in a watershed, and agriculture area in a watershed is one of source areas of nonpoint source (NPS), since soil surface typically exposures due to agricultural activities. Especially, severe sediment might flow into stream when agricultural area is located near stream like the Imha-dam watershed. Soil erosion is affected by precipitation, therefore there is a need to consider precipitation characteristics in soil erosion and best management practices (BMPs) simulation. The Web-based Spreadsheet Tool for the Estimation of Pollutant Load (STEPL WEB) allows estimating long-term sediment loads and the impact of best management practices to reduce sediment loads. STEPL WEB and predicted precipitation data by MIROC-ESM model was used to estimate sediment loads and its reduction by filter strip and conversion of agricultural area to forest in the future 30 years. The result indicates that approximately 70 % of agricultural area requires filter strip installation or that approximately 50 % of agricultural area needs to be converted to forest, for 41 % of sediment load reduction.

• Journal of Wetlands Research
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• v.19 no.1
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• pp.37-44
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• 2017

Nonpoint source (NPS) pollution continues to degrade the water quality. NPS pollutants signals high concerns against a sustainable environment. Low impact development (LID) is the leading management practice which regulates and treats stormwater runoff especially in highly impervious urban areas. Constructed wetlands are known to have efficient removal capability of NPS pollutants. Likewise, these LID facilities were intended to maintain the predeveloped hydrologic regime through series of mechanisms such as particle settling, filtration, plant uptake, and etc. In this study, the objective was to investigate the characteristics, fate and treatment performance of the two in-campus constructed wetlands (SW1 and SW2) which were installed adjacent to impervious roads and parking lots to treat stormwater runoff. A total of 42 storm events were monitored starting from July 2010 until November 2015. Manual grab sampling was utilized at the inlet and outlet units of each LID facilities. Based on the results, the wetlands were found to be effective in reducing 37% and 41% of the total runoff volume and peak flows, respectively. Aside from this, outflow EMCs were generally lower than the inflow EMCs in most events suggesting that the two wetlands improved the water quality of stormwater runoff. The average removal efficiency of pollutants in facilities were 63~79% in TSS, 38~54% in TN, 54% in TP and 32%~81% in metals. The results of this study recommend the use of constructed wetlands as efficient treatment facility for urban areas for its satisfactory performance in runoff and pollutant reduction.

• Journal of Environmental Impact Assessment
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• v.23 no.5
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• pp.393-405
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• 2014

In this study, the nonpoint sources were evaluated by calculating the Nadonggang basin regional water quality and nonpoint source pollution load discharged. And were selected the banks of first administration based on the results and the direction of the next administration. As a results of estimating the water quality about BOD concentration in the mid influence area in the Nakdonggang basin, it was founded that 10 sites for 'Ia' water quality level, 6 sites for 'lb' water quality level, 5 sites for 'II' water quality level, 1 sites for 'I' water quality level. The estimation of COD concentration in the mid influence area, It showed that 9 sites for 'Ib' water quality level, 6 sites for 'II' water quality level, 6 sites for 'III' water quality level, 1 site for 'IV' water quality level. The assessment of water quality made Mid influence area of Gumhogang, Nakdong Goryung, Nakdong Milyang and Namgang selected as the mid influence area of high pollution. And delivery loads of nonpoint sources were calculated for mid influence area in Nakdonggang basin(max delivery load : 17,706.7 kg/day for Gumhogang influence area). As the result of calculating NPS(nonpoint sources) delivery load and water quality at influence area in Nakdonggang basin, Gumhogang influence area was selected as an area for management priority among nonpoint sources.