• Journal of Korea Water Resources Association
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• v.52 no.3
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• pp.187-194
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• 2019

Intake ratio from river constitutes about 31% (8/26) that beings to "water stress country" as "Medium ~ High" with China, India, Italy, South Africa, etc. Therefore, the present study on a dam that is the most effective and direct for securing water resources has been performed. First of all, climate change scenarios were investigated and analyzed. RCP 4.5 and 8.5 with 12.5 km grid resolution presented in the IPCC (Intergovernmental Panel on Climate Change) 5th Assessment Report (AR5) were applied to study watershed using SWAT (Soil and Water Assessment Tool) and HEC-ResSim models that carried out co-operation. Based on the results of dam simulation, the reduction effects of floods and droughts were quantitatively presented. The procedures of dam projects of the USA, Japan and Korea were investigated. As a result, there are no estimating quantitative criteria, calculating methods or formulas. In the present study, therefore, indexes for selecting suitable dam site through literature investigation and analyzing dam watersheds were determined, Expert questionnaire for various indexes were performed. Based on the above mentioned investigation and expert questionnaire, a methodology assigning weight using AHP method were proposed. The function of suitable dam (FSDS) site was calibrated and verified for four medium-sized watersheds. Finally, automated model for suitable dam site was developed using FSDS and 'Model builder' of GIS tool.

• Journal of Soil and Groundwater Environment
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• v.26 no.6
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• pp.118-129
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• 2021

The sediment transportation caused by soil erosion due to rainfall-discharge in the large watershed scale plays critical role in human society. The relationship between rainfall-discharge-sediment transportation is depending on the start time of rainfall and end of rainfall but, the studies related with rainfall characteristics are insufficient. In this study, The Soil and Water Assession Tool (SWAT) model was used to study the relationship between rainfall-discharge-sediment transportation at the Sook river watershed which is monitored by the Ministry of Environment. To do this, first of all, the sensitivity analysis about model attributes was performed using monitored data. The accuracy analysis of SWAT model was conducted using the model's efficiency index (Nash and Sutcliffe model efficiency; NSE) and the coefficient of determination (R²). After that, it was studied what results could be obtained according to changes in rainfall timing and end points. In the result of discharge simulation, the modified rainfall values (sum of total rainfall starting time and end time) showed more high accuracy values (R²:0.90, NSE: 0.8) than original rainfall values (R²:0.76, NSE: 0.72). In the result of sediment transportation simulation, during calibration had more resonable results(R²:0.87, NSE: 0.86) than compared with original rainfall values (R²:0.44, NSE: 0.41). However, validation results of sediment transportation simulation showed low accuracy values compared with calibration results. This results maybe cause monitoring periods of sediment flow compared with discharge monitoring periods. Nevertheless, since rainfall characteristic plays critical rule in model results, continuous research on rainfall characteristic is needed.

• Journal of Korea Water Resources Association
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• v.40 no.3
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• pp.251-263
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• 2007

In this paper, we constructed the integrated watershed model system, SWAT-Nak Dong that include areal mean precipitaiton, runoff and water balance components in the Nak Dong river basins and with this model system we are capable of estimating streamflows for ungaged river stations and analyzing the variations of the streamflows. SWAT(Soil and Water Assessment Tool) is a conceptual, continous time model that was developed in the early 1990s to assist water resource managers in assessing the impact of management and climate on water supplies and non-point source pollution III watersheds and large river basins. Using the SWAT-Nak Dong system and various scenarios, we analyzed and evaluated the dams and water uses effects on the streamflows.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.101-101
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• 2021

본 연구에서는 금강 유역(9,645.5 km²)을 대상으로 SWAT(Soil and Water Assessment Tool)을 이용하여 장기간 지하수 양수와 산림 성장이 수문에 미치는 영향을 평가하였다. 1976년부터 2015년까지 40년의 지하수 이용량(GU)과 산림 성장(FG) 자료를 10년 단위(1980s; 1976~1985, 1990s; 1986~1995, 2000s; 1996~2005, 2010s; 2006~2015)로 구축하고, SWAT 입력자료와 증발산량 매개변수로 사용하여 연대별 지하수 양수와 산림 생장을 반영하였다. 금강 유역 내 위치한 2개의 다목적댐과 3개의 다기능 보에서 관측된 일별 유량으로 2006년부터 2015까지 10년을 검·보정하여 모델의 적용성을 검증하였다. 5지점에 대한 검보정 결과, NSE는 0.76에서 0.79, R²는 0.78에서 0.81, RMSE는 0.55 mm/day에서 1.96 mm/day, PBIAS는 -5.48%에서 8.56%로 통계적으로 유의한 수준으로 분석되었다. 적용성을 검증한 SWAT에 각 연대에 맞는 GU와 FG 정보를 입력하여 수문을 모의하였으며, 두 요인이 물순환에 미치는 영향을 평가하기 위하여 기상조건은 2010s로 고정하였다. 모의결과, GU와 FG 변화가 주는 영향으로 유역 출구의 총유출량은 7.8%(60.7 mm/year) 감소하였으며, 1980s과 2010s에서 각각 775.0 mm/year, 714.3 mm/year의 값을 보였다. 물순환 분석 결과, 지표유출, 중간유출, 기저유출, 침투량, 토양수분은 감소하는 경향을 보였고, 증발산량과 지하수 충전량(GWR)은 증가하는 경향을 보였다. GU의 증가로 인한 지하수위의 지속적인 감소가 GWR이 증가하는 원인으로 판단하였으며, 강우 기간에 포장용수량 이상의 토양수가 빠르게 흘러 지하수 충전량을 증가시켰다고 추론하였다. 또한, 유황 곡선을 분석한 결과, 유량이 지하수 양수와 산림 생장에 영향을 받은 지역에서 시간 흐름에 따라 감소하였고, 저유량 구간에서 상대적으로 많이 감소하였다.

• Journal of Korea Water Resources Association
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• v.51 no.12
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• pp.1195-1205
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• 2018

In the study, the water shortage of Boryeong Dam watershed ($163.6km^2$) was evaluated under future climate change scenario. The Soil and Water Assessment Tool (SWAT) was used considering future dam release derived from multiple linear regression (MLR) analysis. The SWAT was calibrated and verified by using daily observed dam inflow and storage for 12 years (2005 to 2016) with average Nash-Sutcliffe efficiency of 0.59 and 0.91 respectively. The monthly dam release by 12 years MLR showed coefficient of determination ($R^2$) of above 0.57. Among the 27 RCP 4.5 scenarios and 26 RCP 8.5 scenarios of GCM (General Circulation Model), the RCP 8.5 BCC-CSM1-1-M scenario was selected as future extreme drought scenario by analyzing SPI severity, duration, and the longest dry period. The scenario showed -23.6% change of yearly dam storage, and big changes of -34.0% and -24.1% for spring and winter dam storage during 2037~2047 period comparing with 2007~2016 period. Based on Runs theory of analyzing severity and magnitude, the future frequency of 5 to 10 years increased from 3 in 2007~2016 to 5 in 2037~2046 period. When considering the future shortened water shortage return period and the big decreases of winter and spring dam storage, a new dam operation rule from autumn is necessary for future possible water shortage condition.

• Journal of Wetlands Research
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• v.10 no.2
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• pp.39-51
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• 2008

In recent days, the cases of using wetlands in treating waste water, storm events, mining leachate, and agriculture effluents are increasing. But there is the lack of the data for wetlands because of the difficulty in long term monitoring. Such an aspect makes the proper use of wetland impractical. In this study for the purpose of generating a long term hydrologic data, the time series of storage amount for Upo, Mokpo, Sajipo, and Jjokjibeol in Topyeong watershed is simulated using SWAT model. Based on the SWAT-Topyeong model involved in several scenarios for constructing new washlands in Topyeong watershed, the temporal behavior of new washlands is analyzed. It is also revealed that the constructed washland can affect the Upo in some degrees.

• Journal of Korean Society on Water Environment
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• v.28 no.4
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• pp.495-504
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• 2012

In recent years, urbanization has been a hot issues in watershed management due to increased pollutant loads from impervious urban areas. The Soil and Water Assessment Tool (SWAT) model has been widely used in hydrology and water quality studies at watershed scale. However, the SWAT has limitations in simulating water flows between HRUs and hydrological effects of LID practices. The Storm Water Management Model (SWMM) has LID capabilities, but it does not simulate non-urban areas, especially agricultural areas. In this study, a SWAT-SWMM coupled model was developed to evaluate effects of LID practices on hydrology and water quality at mixed-landuse watersheds. This coupled SWAT-SWMM was evaluated by comparing calibrated flow with and without coupled SWAT-SWMM. As a result of this study, the $R^2$ and NSE values with SWAT are 0.951 and 0.937 for calibration period, and 0.882 and 0.875 for validation period, respectively. the $R^2$ and NSE values with SWAT-SWMM are 0.877 and 0.880 for validation period. Out of four LID scenarios simulated by SWAT-SWMM model, the green roof scenario was found to be most effective which reduces about 25% of rainfall-runoff flows.

• Proceedings of the Korea Water Resources Association Conference
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• 2016.05a
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• pp.291-291
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• 2016

토지이용변화는 환경 변화에 영향을 주는 대표적인 인자이기 때문에 수문 모델링에 있어서 상당히 중요하다. 특히 급격한 도시화가 이루어지는 지역에 대해서는 토지이용변화를 반드시 고려하여야 한다. 인구와 지형자료를 이용하여 토지이용변화를 모의할 수 있는 CLUE-S 모델이 개발되었지만 아직까지 대부분 수문모델은 토지이용변화를 고려하지 못하고 있었다. 이에 Pai, N. 와 D. Saraswat은 SWAT2009_LUC Tool를 개발하여 시공간적으로 변화하는 토지를 고려한 수문모의를 가능하도록 하였다. 하지만 SWAT2009_LUC는 새로운 종류의 토지이용종류를 고려할 수 없어 유역 내 새로운 토지이용도가 추가될 시 이를 모의할 수 없다는 단점을 가지고 있다. 이러한 단점을 극복하기 위해서 Friedrich J. Koch Koch는 Land use Update and Soil Assessment(LUPSA)를 개발하여 새로운 토지이용도 및 변화된 토지이용도의 경사도를 추가적으로 고려할 수 있도록 하였다. 하지만 LUPSA 모듈은 공개되어 있지 않다. 따라서 본 연구에서는 SWAT 사용자들이 토지이용변화를 많이 고려할 수 있도록 Web 기반의 LUC 모듈을 개발하였으며, SWAT BFlow Alpha Factor와 경사도 기반의 CN을 산정할 수 있는 모듈을 추가하였다. 본 연구에서 개발된 Web 기반의 LUC는 국내뿐만 아니라 해외 SWAT 사용자들로 하여금 급격하게 토지가 변화한 유역에 대해 정확한 수문모의를 하는데 기여할 것이라 판단된다.

• Journal of Korean Society on Water Environment
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• v.32 no.2
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• pp.149-162
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• 2016

In recent years, there has been demand for precise estimations of pollutant loads on nationwide scale for the development of appropriate site specific (watershed specific) policies to reduce the negative impact of pollutant loads. River flow data and water quality data that were previously collected by various research institutes and universities for specific research purposes for a limited period was utilized in this study. However, only TMDL 8-day interval flow and water quality data were available in national scale. Three watersheds were selected and pollutant loads were calculated by two methods i.e., Numeric Integration (NI) method and Soil and Water Assessment Tool (SWAT). Subsequently, the results were compared to determine the appropriate method for monitoring nonpoint source networks nationwide. The SWAT model was calibrated and its estimated daily flow data were used in the NI method with estimated sediment data for 8-day monitoring data for three watersheds. The results indicated that the quantity of pollutant loads estimated with the NI and SWAT are different to some degrees especially during the summer season for all the three study watersheds. Thus, more frequent sampling of water quality is needed for nonpoint source pollutant estimation.

• Proceedings of the Korea Water Resources Association Conference
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• 2018.05a
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• pp.43-43
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• 2018

수생태계는 다른 여러 생태계 중에서 가장 위험에 처해있으며, 기후변화로 인한 수온, 수문 수질의 변화는 수생태계와 담수 생물다양성에 가장 큰 영향을 미치는 요인 중 하나이다. 본 연구에서는 생물 생태학적으로 변화하는 세계적인 물 관리 패러다임에 따라 한강유역에서의 미래 수생태계 평가를 수행하였다. 본 연구의 목적은 수생태 건강성 관측자료와 수질자료, SWAT 모형을 이용하여 미래 기후변화에 따른 한강유역의 수생태를 평가하는 것이다. 본 연구에서 선정한 수생태계 건강성 조사자료로 국립환경과학원에서 8년간(2008년~2015년) 봄과 가을 2차례에 걸쳐 모니터링 한 부착돌말류(TDI), 저서형 대형무척추동물(BMI), 어류(FAI)에 대한 수생태 등급자료 및 해당 지점에 대한 수온 및 수질자료를 이용하였다. 수집한 결과를 DB(T-N, $NH_4N$, $NO_3N$, T-P, PO4P)에 대한 수생태 등급의 상관성을 분석하고 수온 수질인자에 따른 수생태 등급을 나타내어 미래 기후변화에 따른 수생태 건강성 평가 및 예측을 실시하고자 하였다. Soil and Water Assessment Tool (SWAT) 모형은 유역의 신뢰성 있는 유역 수문, 수질 모의 및 기후변화 영향평가를 위하여 활용되었다. SWAT 모형을 이용하여 한강유역의 다목적댐(3개), 발전용댐(1개), 다기능보(3개) 운영을 고려하였고, 237개의 표준유역으로 분할한 뒤 수문 및 수질 모의를 수행하였다. 모형의 적용성 평가를 위해 댐 및 보의 유입량, 증발산량, 토양수분, 지하수위, SS, T-N, T-P에 대하여 보정(2005~2009) 및 검증(2010~2015)을 수행하였다. 기후변화에 따른 수문, 수질 및 수생태 평가를 위해 기상청의 HadGEM3-RA RCP 4.5와 8.5 시나리오를 적용하였으며, 기준년(1975-2005)년에 대해 2020s(2010-2039), 2050s(2040-2069), 2080s(2070-2099)의 수생태를 평가하였다.