• Journal of Korean Society on Water Environment
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• v.27 no.1
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• pp.61-72
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• 2011

In order to assess hydrologic and nonpoint source pollutant behaviors in a watershed with Soil and Water Assessment Tool (SWAT) model, the accuracy evaluation of SWAT model should be conducted prior to the application of it to a watershed. When calibrating and validating hydrological components of SWAT model, the Nash-Sutcliffe efficiency coefficient (EI) has been widely used. However, the EI value has been known as it is affected sensitively by big numbers among the range of numbers. In this study, a Web-based flow clustering EI estimation system using K-means clustering algorithm was developed and used for SWAT hydrology evaluation. Even though the EI of total streamflow was high, the EI values of hydrologic components (i.e., direct runoff and baseflow) were not high. Also when the EI values of flow group I and II (i.e., low and high value group) clustered from direct runoff and baseflow were computed, respectively, the EI values of them were much lower with negative EI values for some flow group comparison. The SWAT auto-calibration tool estimated values also showed negative EI values for most flow group I and II of direct runoff and baseflow although EI value of total streamflow was high. The result obtained in this study indicates that the SWAT hydrology component should be calibrated until all four positive EI values for each flow group of direct runoff and baseflow are obtained for better accuracy both in direct runoff and baseflow.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.2
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• pp.529-536
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• 2013

The semi-distributed rainfall runoff model of SWAT is applied to the Seom-river experimental watershed. The simulations of various antecedent periods before the targeted simulation periods of 2002 to 2009 are not necessary despite of the slight appearance of corresponding changes in simulated total runoff. The simulated results of total runoff by using various numbers of soil layer maps have little differentiated nevertheless the slight changes in simulated results have been appeared. The 7 parameters of CANMX, $CN_2$, ESCO, GW_REVAP, SOL_ALB, SOL_AWC, and SOL_K greatly govern the rainfall runoff are confirmed and their sensitivity analyses have been carried out. The optimal parameters used in SWAT are derived by SUFI-2 of SWAT-CUP. The NS and $R^2$ are 0.99 and 0.98, respectively which is shown the good agreement between the observed and the simulated results. The uncertainty factors of P-factor and R-factor are 0.85 and 0.06, respectively which is also shown the high efficiency of the model. The high applicability is also shown with improving the RMSE in SWAT model simulation using the parameters estimated by SUFI-2 of SWAT-CUP.

• Proceedings of the Korea Water Resources Association Conference
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• 2009.05a
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• pp.2068-2072
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• 2009

본 연구에서는 국내에서 널리 사용되는 대표적 유역모형인 SWAT 모형의 한계를 인식하고 유출해석모듈과 하도수질모듈을 개선한 SWAT-K(Korea) 모형이 현재 오염총량관리 대상물질로 지정되어 있는 BOD 모의에 미치는 영향을 분석하기 위하여 충주댐유역을 대상으로 각 개선모듈별 BOD 모의 결과를 분석하였다. 유출해석모듈의 개선결과 하도의 흐름을 따라 이동하는 BOD 항목의 모의 특성 상 유출 구조의 개선에 의하여 BOD 부하량의 지체가 감소되며 첨두 부하량이 증가한 것을 확인할 수 있었다. 하도수질모듈의 개선결과 저유량 시 매개변수 산정에도 불구하고 증가하지 않던 값들이 모형의 개선에 의하여 정상적인 범위로 상승한 것을 확인할 수 있었다. 전체적인 개선에 의하여 각 모듈별 개선효과와 함께 충주댐 지점의 개선 전 후 일대일 비교를 수행한 결과 결정 계수($R^2$)가 0.54에서 0.88로 상승하며 개선 후 모의값이 실측값에 근사하게 모의되는 것을 확인할 수 있었다.

• Journal of the Korean Association of Geographic Information Studies
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• v.9 no.3
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• pp.136-145
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• 2006

SWAT includes a lot of parameters related with geography, hydrological time series, land management and water pollution, etc. So, it needs many spatial, non-spatial and time series data to run SWAT. If SWAT is operated in conjunction with GIS, we can use database which includes model input data and do all the processes which covers data creation, model input and analysis of simulation results in a system. The objective of this study is to develop HyGIS-SWAT which is the interface system to couple the SWAT model and HyGIS. To achieve this object, system operation process based on HyGIS-SWAT data model is evaluated and databases are designed and established. As a result, HyGIS-SWAT prototype system is developed. HyGIS data model and HyGIS-Model operation process can be applied effectively to the development of HyGIS-SWAT. The technologies from this study can be used as base technology to develop another HyGIS application which connect HyGIS with models.

• Proceedings of the Korea Water Resources Association Conference
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• 2009.05a
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• pp.2014-2017
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• 2009

유출량과 수질자료는 하천을 관리하는데 있어 필수적인 수문자료이다. 미계측 유역의 경우 유출량은 면적비유량법 및 강우-유출모형을 통해서 유출량을 산정하고 있다. 강우-유출 모형에는 HEC-1, HEC-HMS, SWMM등의 여러 가지 모형이 쓰이고 있으며, 수질자료는 Qual2K, Qual2E 등의 모델을 이용하여 자료를 산출하고 있다. 기존의 모델들은 토지이용과 토양의 특성을 반영하기 어렵다. 토지이용과 토양의 특성을 반영하기 어려웠던 기존의 모형과는 달리 SWAT(Soil And Water Assessment Tool) 모형의 경우 GIS(Geographic Information system)를 이용함으로써 정확한 토지이용과 토양특성을 적용할 수 있다는 장점이 있으며, 시 공간적 변화를 고려할 수 있다. 또한, 유역을 소유역으로 세분화함으로써 수문학적 응답 단위(Hydrologic Response unit : HRU)로 계산이 가능하여 더욱 세밀한 모의가 가능하다. 본 연구에서는 SWAT모형을 전남 나주시와 화순군에 걸쳐 흐르는 지석천 유역에 적용하여 유출량과 수질을 모의함으로써 실제유역과 유사한 물리적 모의를 실행하였다. 그 결과 SWAT모형이 대상지역의 부하량과 유출량 모의에 높은 적용성을 나타냈다.

• Proceedings of the Korea Contents Association Conference
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• 2010.05a
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• pp.325-327
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• 2010

장기강우유출 현상에 대한 정확한 이해는 수자원의 질과 양적 관리를 위한 필수적 사항으로 수자원 분야에서 활발히 연구되어 왔다. 특히 수자원의 보존 및 관리측면에서 장기강우에 의한 정확한 유출량 예측은 매우 중요하다. SWAT 모형은 토양과 토지이용 및 관리상태에 따라 복잡하게 반응하는 유역의 유출거동 모의를 위해 개발된 모델이다. 본 연구에서는 GIS를 이용하여 복잡한 유역에 대한 지형인자정보를 효과적으로 구축하여 SWAT 모형을 사용함으로써 진양호의 일유입량을 추정하였다. GIS와 연계된 SWAT 모형을 통해 남강댐으로 유입되는 일유입량을 예측하고자 관련매개변수들을 최적화하였으며, 검증기간에 대한 모의를 통하여 본 모델이 장기 일유출량 뿐만 아니라 유역의 연유출량 추정에도 효과적으로 적용될 수 있음을 확인할 수 있었다.

• 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.

• Journal of The Korean Society of Agricultural Engineers
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• v.54 no.2
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• pp.137-145
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• 2012

본 연구에서는 2005년부터 2006년까지 충청남도 공주시 반포면에 위치한 봉곡천 유역의 경사지 밭을 포함하고 있는 산지하천에서 유출량, 총인, 총질소를 측정하였고 측정된 자료는 SWAT 모형을 통하여 장기간의 배출부하량 산정을 위해 모형의 보정 및 검정자료로 사용하였다. SWAT 모형의 보정 및 검정결과는 유출량은 일별자료를 이용하여 보정 및 검정을 실시하였다. 그 결과 결정계수 ($R^2$)가 0.80~0.83의 값을 보였으며 일별 T-N, T-P 부하량에 대한 보정 및 검정결과는 결정계수 ($R^2$)가 0.62~0.86의 값을 보였다. 모형의 보정 및 검정을 통해 결정된 최적매개변수를 적용하여 1997년부터 2006년까지 관측된 강우자료로 장기간의 유출량, T-N, T-P 배출부하량에 대한 SWAT 모형 시뮬레이션을 수행하였다. 또한 이를 바탕으로 하여 산지와 밭에 대한 원단위를 산정하였으며, 그 결과 산지에 대한 T-N의 원단위는 3.29 $kg/km^2/day$이었고 T-P에 대한 원단위는 0.15 $kg/km^2/day$로 나타났다. 또한 밭에서의 T-N에 대한 원단위는 11.15 $kg/km^2/day$이었고 T-P에 대한 원단위는 0.70 $kg/km^2/day$로 나타났으며 강우의 시간 및 공간적 변화에 따른 유출량을 고려한 산지와 밭에서의 영양염류 배출부하량을 산정하는데 SWAT모형을 적용하는 것이 타당성이 있는 것으로 판단되었다.

• Journal of Korea Water Resources Association
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• v.41 no.10
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• pp.969-982
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• 2008

As hydrological models have been progressively developed, they are recognized as appropriate tools to manage water resources. Especially, the need to evaluate the effects of landuse and climate change on hydrological phenomena has been increased, which requires powerful validation methods for the hydrological models to be employed. As measured streamflow data at many locations may not be available, or include significant errors in application of hydrological models, streamflow data simulated by models only might be used to conduct hydrological analysis. In many cases, reducing errors in model simulations requires a powerful model validation method. In this research, we demonstrated a validation methodology of SWAT model using observed flow in two basins with different physical characteristics. First, we selected two basins, Gap-cheon basin and Yongdam basin located in the Guem River Basin, showing different hydrological characteristics. Next, the methodology developed to estimate parameter values for the Gap-cheon basin was applied for estimating those for the Yongdam basin without calibration a priori, and sought for validation of the SWAT. Application result with SWAT for Yongdam basin showed $R_{eff}$ ranging from 0.49 to 0.85, and $R^{2}$ from 0.49 to 0.84. As well, comparison of predicted flow and measured flow in each subbasin showed reasonable agreement. Furthermore, the model reproduced the whole trends of measured total flow and low flow, though peak flows were rather underestimated. The results of this study suggest that SWAT can be applied for predicting effects of future climate and landuse changes on flow variability in river basins. However, additional studies are recommended to further verify the validity of the mixed method in other river basins.

• Journal of Korea Water Resources Association
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• v.45 no.3
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• pp.301-316
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• 2012

Two models, TANK and SWAT (Soil and Water Assessment Tool) were compared for simulating natural flows in the Paldang Dam upstream areas of the Han River basin in order to understand the limitations of TANK and to review the applicability and capability of SWAT. For comparison, simulation results from the previous research work were used. In the results for the calibrated watersheds (Chungju Dam and Soyanggang Dam), two models provided promising results for forecasting of daily flows with the Nash-Sutcliffe model efficiency of around 0.8. TANK simulated observations during some peak flood seasons better than SWAT, while it showed poor results during dry seasons, especially its simulations did not fall down under a certain value. It can be explained that TANK was calibrated for relatively larger flows than smaller ones. SWAT results showed a relatively good agreement with observed flows except some flood flows, and simulated inflows at the Paldang Dam considering discharges from upper dams coincided with observations with the model efficiency of around 0.9. This accounts for SWAT applicability with higher accuracy in predicting natural flows without dam operation or artificial water uses, and in assessing flow variations before and after dam development. Also, two model results were compared for other watersheds such as Pyeongchang-A, Dalcheon-B, Seomgang-B, Inbuk-A, Hangang-D, and Hongcheon-A to which calibrated TANK parameters were applied. The results were similar to the case of calibrated watersheds, that TANK simulated poor smaller flows except some flood flows and had same problem of keeping on over a certain value in dry seasons. This indicates that TANK application may have fatal uncertainties in estimating low flows used as an important index in water resources planning and management. Therefore, in order to reflect actually complex and complicated physical characteristics of Korean watersheds, and to manage efficiently water resources according to the land use and water use changes with urbanization or climate change in the future, it is necessary to utilize a physically based watershed model like SWAT rather than an existing conceptual lumped model like TANK.