• 한국물환경학회지
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• 제28권3호
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• pp.409-417
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• 2012

SWAT model was applied for the Nakdong River Basin to characterize water quality variability and assess the feasibility of using the load duration curve to water quality management. The basin was divided into 67 sub-basins considering various watershed environment, and rainfall runoff and pollutant loading were simulated based on 6 year measurements of meteo-hydrological data, discharge data of treatment plants, and water quality data (SS, T-N and T-P). The results demonstrate that non-point source loads during wet season increase by 80 ~ 95% of total loads. Although the rate of water flow governs the amount of SS that is transported to the main streams, nutrient concentrations are highly elevated during dry season by being concentrated. This phenomenon is more pronounced in the lower basin, receiving large amounts of urban point source discharges such as treated sewages. Also, the load duration curves (LDC) demonstrate dominant source problems based on the load exceedances, showing that SS concentrations are associated with the rainy season and nutrients, such as T-P, may be more concentrated at low flow and more diluted at higher flow. Overall, the LDC method could be used conveniently to assess watershed characteristics and pollutant loads in watershed scale.

• 한국물환경학회지
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• 제24권4호
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• pp.465-472
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• 2008

Soil and Water Assessment Tool (SWAT) model was selected as a tool for assessing the effect of pollutant sources on the total loads from the Chungju Dam upstream watershed. The model was constructed through calibration of parameters related to nitrogen (N) and phosphorus (P), which was based on the runoff and sediment modeling performed in the previous research. Using this, the spatial and temporal pollutant loadings by source type were investigated. Results of this study indicated that in most forested upstream sub-watersheds, pollutant loadings from point sources were very low, and total loadings by point and non-point sources were also insignificant. On the other hand, in #14 sub-watershed including Jecheon city, the loadings by point source were relatively considerable. For the whole watershed, non-point sources accounted for 99% of sediment, 97% of N, and 93% of P loads. And monthly non-point source loadings were concentrated on rainy summer season, while point source loadings of N and P kept nearly constant throughout the year and were high on dry winter season relative to non-point source.

• 한국농공학회지
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• 제44권7호
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• pp.25-35
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• 2002

In this study, the effect of DEM (Digital Elevation Model) resolution (15m, 30m, 50m, 70m, 100m, 200m, 300m) on the hydrological simulation was examined using the BASINS (Better Assessment Science Integrating point and Nonpoint Source) for the Heukcheon watershed (303.3 ㎢) data from 1998 to 1999. Generally, as the cell size of DEM increased, topographical changes were observed as the original range of elevation decreased. The processing time of watershed delineation and river network needed more time and effort on smaller cell size of DEM. The larger DEM demonstrated had some errors in the junction of river network which might affect on the simulation of water quantity and quality. The area weighted average watershed slope became milder but the length weighted average channel slope became steeper as the DEM size increased. DEM resolution affected substantially on the topographical parameter but less on the hydrological simulation. Considering processing time and accuracy on hydrological simulation, DEM grid size of 100m is recommended for this range of watershed size.

• 농업과학연구
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• 제48권3호
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• pp.629-642
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• 2021

Land-use change has an important role in the hydrologic characteristics of watersheds because it alters various hydrologic components such as interception, infiltration, and evapotranspiration. For example, rapid urbanization in a watershed reduces infiltration rates and increases peak flow which lead to changes in the hydrologic responses. In this study, a physical hydrologic model the soil and water assessment tool (SWAT) was used to assess long-term continuous daily streamflow corresponding to land-use changes that occurred in the Naesungchun river watershed. For a 30-year model simulation, 3 different land-use maps of the 1990s, 2000s, and 2010s were used to identify the impacts of the land-use changes. Using SWAT-CUP (calibration and uncertainty program), an automated parameter calibration tool, 23 parameters were selected, optimized and compared with the daily streamflow data observed at the upstream, midstream and downstream locations of the watershed. The statistical indexes used for the model calibration and validation show that the model performance is improved at the downstream location of the Naesungchun river. The simulated streamflow in the mainstream considering land-use change increases up to -2 - 30 cm compared with the results simulated with the single land-use map. However, the difference was not significant in the tributaries with or without the impact of land-use change.

• 한국농공학회논문집
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• 제61권4호
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• pp.87-96
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• 2019

The objective of this study was to develop a general inundation modeling technique considering the effect of drainage delay in the paddy field districts. In most studies, farmland inundation simulations have been conducted using previously developed watershed models. However, the water cycle in the paddy fields has a different structure from that of the general watershed, and the effect of the drainage delay should be considered. In this study, the drainage delay algorithm was developed using water balance equation, and the inundation modeling was performed for inundation-prone paddy fields located near Doowol stream. As a result, the depth of inundation was 43.1 cm and 45.2 cm, respectively, due to the 100-year and 200-year frequency rainfall. With the operation of drainage pump ($0.1m^3/s$), inundation depths decreased by 5.8 cm and 6.0 cm, respectively, and inundation time reduced by 20 hours and 21 hours, respectively for the 100-year and 200-year frequency rainfall. The result showed that the general inundation modeling technique developed in this study could reflect the effect of drainage delay due to the rise of external water level and the flooding reduction effect by operation of drainage pump. The results of this study are expected to be useful to establish measures for damage caused by farmland inundation.

• 대한환경공학회지
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• 제27권12호
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• pp.1340-1346
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• 2005

소수계 물관리 진단시스템, CREEK-1을 이용하여 합류식 하수관거 월류수 발생시 청계천에서 나타나는 수질변화에 관한 모델 연구를 수행하였다. CREEK-1은 지리정보시스템, 데이터베이스, 경관생태모델(FRAGSTATS), 유역모델(SWMM), 수질모델(WASP5), 그리고 컴퓨터 그래픽으로 구성되어있다. 본 연구에서는 강우시 청계천의 수질변화를 시뮬레이션하기 위해 유역모델과 수질모델이 주로 사용되었다. 유역모델에서 청계천 전체 유역이 18개의 소유역으로, 수질모델에서 대상 하천 구간은 11개의 구획으로 나누어져 모델이 구성되었다. 유역모델은 강우시 현장에서 관측된 BOD, 총질소, 총인 그리고 유량 자료로 타당성이 검토되었으며, 그 결과 모든 항목에서 모델 예측같은 관측값과 비교적 적절한 일치를 보였다. 연구 결과는 하천의 수질이 강우량과 강우 시작 후 경과 시간에 따라 변화가 일어나고 있음을 보여주었다. 강우 초기에는 유역의 초기 세척수와 CSO에서 차지하는 하수 비율이 높기 때문에 수질이 크게 악화되었으나 유출 수량이 증가함에 따라 희석효과에 의해 수질이 개선되는 것으로 나타났다.

• 한국농공학회논문집
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• 제57권4호
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• pp.121-133
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• 2015

The TANK model has been widely used in rainfall-runoff modeling due to its simplicity of concept and computation while achieving forecast accuracy. A major barrier to the model application is to determine parameter values for ungauged watersheds, leading to the need of a method for the parameter estimation. The objective of this study was to develop regression equations for estimating the 3th TANK model parameters considering their variations for the ungauged watersheds. Thirty watersheds of dam sites and stream stations were selected for this study. A genetic algorithm was used to optimize TANK model parameters. Watershed characteristics used in this study include land use percent, watershed area, watershed length, and watershed average slope. Generalized equations were derived by correlating to the optimized parameters and the watershed characteristics. The results showed that the TANK model, with the parameters determined by the developed regression equations, performed reasonably with 0.60 to 0.85 of Nash-Sutcliffe efficiency for daily runoff. The developed regression equations for the TANK model can be applied for the runoff simulation particularly for the ungauged watersheds, which is common for upstream of agricultural reservoirs in Korea.

• 한국물환경학회지
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• 제35권6호
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• pp.470-480
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• 2019

The Doam lake watershed was designated as a non-point pollution management area in 2007 to improve water quality based on watershed management implementation. There have been studies of non-point source reduction with respect to the watershed management impacting the pollutant transport of the reservoir. However, a little attention has been focused on the impact of water quality improvement by the management of the dam operation or the guidelines on the dam operation. In this study, the impact of in-lake management practices combined with watershed management is analyzed, and the appropriate guidelines on the operation of the dam are suggested. The integrated modeling system by coupling with the watershed model (HSPF) and reservoir water quality model (CE-QUAL-W2) was applied for analyzing the impact of water quality management practices. A scenario implemented with sedimentation basin and suspended matter barrier showed decrease in SS concentration up to 4.6%. The SS concentration increased in the scenarios adjusting withdrawal location from EL.673 m to the upper direction(EL.683 m and EL.688 m). The water quality was comparably high when the scenario implemented all in-lake practices with water intake at EL.673 m. However, there was improvement in water quality when the height of the water intake was moved to EL.688 m during the summer by preventing sediments inflow after the rainfall. Therefore, to manage water quality of the Doam lake, it is essential to control the water quality by modulating the height of water intake through consistent turbidity monitoring during rainfall.

• 환경영향평가
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• 제17권4호
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• pp.235-242
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• 2008

To develop a watershed management plan for protection of the lake water quality, the linkages among land use activities, stream water quality, and lake water quality must be understood. This study conducted to develop a Decision Support System(DSS) for the reservoir water quality managers and a comprehensive watershed management plan. This DSS has three main components; database, interactive decision model, and data delivery interface system. Graphic User Interface(GUI) was developed as the interface medium to deliver the data and modeling results to the end users. Water quality management scenarios in Yongdam reservoir consist of two parts. One is the watershed management, and the other is water quality management in the reservoir. The watershed management scenarios that were evaluated include as follows : a removal of point sources, control of waste water treatment plant, reductions in nonpoint sources, and the management of developed land. Water quality management scenarios in the reservoir include to install a curtain wall and to operate an algae removal system. The results from the scenario analysis indicate that the strategy of the reservoir water quality management can promise the best effectiveness to conserve the quality of reservoir water. It is expected that many local agencies can use this DSS to analyze the impact of landuse changes and activities on the reservoir watershed and can benefit from making watershed management decisions.

• 한국농공학회지
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• 제45권4호
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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.