• Journal of Korean Society on Water Environment
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• v.28 no.3
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• pp.347-358
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• 2012

The SWAT (Soil and Water Assessment Tool) should be calibrated and validated with observed data to secure accuracy of model prediction. Recently, the SWAT-CUP (Calibration and Uncertainty Program for SWAT) software, which can calibrate SWAT using various algorithms, were developed to help SWAT users calibrate model efficiently. In this study, three algorithms (GLUE: Generalized Likelihood Uncertainty Estimation, PARASOL: Parameter solution, SUFI-2: Sequential Uncertainty Fitting ver. 2) in the SWAT-CUP were applied for the Soyang-gang dam watershed to evaluate these algorithms. Simulated total streamflow and 0~75% percentile streamflow were compared with observed data, respectively. The NSE (Nash-Sutcliffe Efficiency) and $R^2$ (Coefficient of Determination) values were the same from three algorithms but the P-factor for confidence of calibration ranged from 0.27 to 0.81 . the PARASOL shows the lowest p-factor (0.27), SUFI-2 gives the greatest P-factor (0.81) among these three algorithms. Based on calibration results, the SUFI-2 was found to be suitable for calibration in Soyang-gang dam watershed. Although the NSE and $R^2$ values were satisfactory for total streamflow estimation, the SWAT simulated values for low flow regime were not satisfactory (negative NSE values) in this study. This is because of limitations in semi-distributed SWAT modeling structure, which cannot simulated effects of spatial locations of HRUs (Hydrologic Response Unit) within subwatersheds in SWAT. To solve this problem, a module capable of simulating groundwater/baseflow should be developed and added to the SWAT system. With this enhancement in SWAT/SWAT-CUP, the SWAT estimated streamflow values could be used in determining standard flow rate in TMDLs (Total Maximum Daily Load) application at a watershed.

• Proceedings of the Korea Water Resources Association Conference
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• 2005.05b
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• pp.143-148
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• 2005

The main purpose of this study is to suggest and evaluate an operational method for assessing the potential impact of climate change on hydrologic components and water resources of regional scale river basins. The method, which uses large scale climate change information provided by a state of the art general circulation model(GCM) comprises a statistical downscaling approach and a spatially distributed hydrological model applied to a river basin located in Korea. First, we construct global climate change scenarios using the YONU GCM control run and transient experiments, then transform the YONU GCM grid-box predictions with coarse resolution of climate change into the site-specific values by statistical downscaling techniques. The values are used to modify the parameters of the stochastic weather generator model for the simulation of the site-specific daily weather time series. The weather series fed into a semi-distributed hydrological model called SLURP to simulate the streamflows associated with other water resources for the condition of $2CO_2$. This approach is applied to the Yongdam dam basin in southern part of Korea. The results show that under the condition of $2CO_2$, about $7.6\% of annual mean streamflow is reduced when it is compared with the observed one. And while Seasonal streamflows in the winter and autumn are increased, a streamflow in the summer is decreased. However, the seasonality of the simulated series is similar to the observed pattern and the analysis of the duration cure shows the mean of averaged low flow is increased while the averaged wet and normal flow are decreased for the climate change.

• Journal of Korea Water Resources Association
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• v.38 no.9 s.158
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• pp.699-711
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• 2005

In this study, the U.S. Geological Survey's DR3M-II(Distributed Routing Rainfall-Runoff Model) was applied for small urban drainage. DR3M-II is a watershed model for routing storm runoff through a branched system of pipes and natural channels using rainfall input. The model was calibrated and verified using short term rainfall-runoff data collected from Sanbon basin. Also, the parameters were optimized using Rosenbrock technic. An estimated simulation error for peak discharge was about 7.4 percent and the result was quite acceptable. Results of the sensitivity analysis indicate that the percent of effective impervious area and ${\alpha}$ defining surface slope and roughness were the most sensitive variables affecting runoff volumes and peak discharge for low and high intensity storm respectively. In most cases, soil moisture accounting and infiltration parameters are the variables that give more effects to runoff volumes than peak discharge. Parameter ${\alpha}$ showed the opposite result.

• Journal of The Korean Society of Agricultural Engineers
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• v.52 no.3
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• pp.97-104
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• 2010

The purpose of this study is to evaluate sediment yield reduction under various field slope conditions with rice straw mat. The Vegetative Filter Strip Model-W (VFSMOD-W) and Soil and Water Assessment Tool (SWAT) were used for simulation of sediment yield reduction effect of rice straw mat. The Universe Soil Loss Equation Practice factor (USLE P factor), being able to reflect simulation of rice straw mat in the agricultural field, were estimated for each slope with VFSMOD-W and measured soil erosion values under 5, 10, and 20 % slopes. Then with the regression equation for slopes, USLE P factor was derived and used as input data for each Hydrological Response Unit (HRU) in the SWAT model. The SWAT Spatially Distributed-HRU (SD-HRU) pre-processor module was utilized, moreover, in order to consider spatial location and topographic features (measured topographic features by field survey) of all HRU within each subwatershed in the study watershed. Result of monthly sediment yield without rice straw mat (Jan. 2000 - Aug. 2007) was 814.72 ton/month, and with rice straw mat (Jan. 2000 - Aug. 2007) was 526.75 ton/month, which was reduced as 35.35 % compared without it. Also, during the rainy season (from Jun. to Sep. 2000 - 2007), when without vs. with rice straw mat, monthly sediment indicated 2,109.54 ton and 1,358.61 ton respectively. It showed about 35.60 % was reduced depending on rice straw mat. As shown in this study, if rice straw mat is used as a Best Management Practice (BMP) in the sloping fields, rainfall-driven sediment yield will be reduced effectively.

• Journal of Environmental Science International
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• v.26 no.4
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• pp.411-420
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• 2017

This research aims at comparing the accuracy of flood discharge estimation. For this, we focused on the Oedo watershed of Jeju Island and compared flood discharge by analyzing the values as follows: (1) the concentration of the lumped model (HEC-HMS) and distributed model (Vflo), and (2) the in-situ data using Fixed Surface Image Velocimetry (FSIV). The flood discharge estimation from the HEC-HMS model is slightly larger than the Vflo model results. This result shows that the estimations of the HEC-HMS are larger than the flood discharge data by 4.43 to 36.24% and that of the Vflo are larger by 8.49 to 11%. In terms of the error analysis at the peak discharge occurrence time of each mapping, HEC-HMS is one hour later than the measured data, but Vflo is almost the same as the measured data.

• Journal of Korean Society of Environmental Engineers
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• v.39 no.10
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• pp.581-590
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• 2017

For effective improvement of water quality in Seokmun reservoir, this study implemented various analyses including the tributary water quality and flowrate monitoring, contamination of sediment, investigation of pollution source, selection of priority management target tributary by stream grouping method. The COD concentration of the majority of tributaries in Seokmun reservoir watershed was relatively higher than BOD concentration. The concentration of water pollutants regardless of water quality parameters in Yeokcheon, Dangjincheon, Sigokcheon, Baekseokcheon, small stream in Jinkwanri and Janghangri were higher than the other tributaries. The pollution sources in the Seokmun reservoir watershed were mostly distributed in the population, livestock, and industry. The pollutants, which located in Yeokcheon, Dangjincheon, Baekseokcheon, and small stream in Janghangri selected as priority management target tributary, should be preferentially reduced for improving the water quality in Seokmun reservoir. As the evaluation results of water quality in Seokmun reservoir for the effect of water quality improvement according to various scenarios using water quality model, it was found that the water quality in Seokmun reservoir due to the construction of a wastewater treatment plant for management of pollutants in the watershed would be satisfied the class V of water environment standard in reservoir.

• Korean Journal of Remote Sensing
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• v.29 no.2
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• pp.263-274
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• 2013

In this study we evaluated the hydrological applicability of multi-satellite precipitation estimates. Three high-resolution global multi-satellite precipitation products, the Tropical Rainfall Measuring Mission (TRMM) Multi-satellite Precipitation Analysis (TMPA), the Global Satellite Mapping of Precipitation (GSMaP), and the Climate Precipitation Center (CPC) Morphing technique (CMORPH), were applied to the Coupled Routing and Excess Storage (CREST) model for the evaluation of their hydrological utility. The CREST model was calibrated from 2002 to 2005 and validated from 2006 to 2009 in the Chungju Dam watershed, including two years of warm-up periods (2002-2003 and 2006-2007). Areal-averaged precipitation time series of the multi-satellite data were compared with those of the ground records. The results indicate that the multi-satellite precipitation can reflect the seasonal variation of precipitation in the Chungju Dam watershed. However, TMPA overestimates the amount of annual and monthly precipitation while GSMaP and CMORPH underestimate the precipitation during the period from 2002 to 2009. These biases of multi-satellite precipitation products induce poor performances in hydrological simulation, although TMPA is better than both of GSMaP and CMORPH. Our results indicate that advanced rainfall algorithms may be required to improve its hydrological applicability in South Korea.

• Journal of Korea Water Resources Association
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• v.46 no.11
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• pp.1053-1067
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• 2013

Distributed ecohydrological model which can simulate hydrological components, vegetation and landsurface temperature using practically available input and observed data with minimum parameters is introduced. This model is designed to properly simulate in area with lack of observed data. Parameter estimation and calibration of the model can be carried out with indirectly estimated data (monthly surface runoff by NRCS-CN method and annual actual vaporization by empirical equation) and remote sensing data (NDVI, LST) instead of observed data. We applied this model in the Naeseong creek basin to evaluate the model validity. Firstly, we found the sensitive parameters which largely influence the simulation results by sensitivity analysis, and then hydrological components, vegetation, land-surface temperature, routed streamflow and water temperature were simulated over 10 years (2001 to 2010) using calibrated parameters. Parameters are estimated by optimization method. It is shown that most of grids are well simulated. In the case of streamflow and water temperature, we checked two observed points in the outlet of watershed and it is shown that streamflow and water temperature are properly simulated as well. Hence, it can be shown that this model properly simulate the hydrological components, vegetation, land-surface temperature, routed streamflow and water temperature as well, even though in despite of using limited input data and minimum parameters.

• Journal of Korean Society on Water Environment
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• v.29 no.4
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• pp.466-475
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• 2013

Non-point source pollution management is one of the most important issues in Korean water quality/watershed management. In recent years, Low Impact Development (LID) has emerged as an effective approach to control stormwater in an urban area. This study illustrates how to design and evaluate the effect of non-point pollutant management using EPA-SWMM LID module and suggests design parameters for modeling LID facilities. In addition, optimal installation locations of LID can be determined by a simple distributed hydrologic model by using SWMM for a long-term.

• Proceedings of the Korea Water Resources Association Conference
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• 2009.05a
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• pp.953-956
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• 2009

본 연구는 농업용저수지유역을 대상으로 분포형 강우-유출모형을 적용해 봄으로서 차후 본 연구대상유역의 분포형 강우유출모형을 이용한 설계홍수량 산정에 활용해 보기 위한 사전연구이다. 농업용저수지유역을 대상으로 모의하기 위하여 자동수위계를 통하여 저수지 수위자료가 주기적으로 기록되고 있는 계룡저수지 유역($15.4km^2$)을 선정하였으며, 주요 공간매개변수는 30m 격자해상도로 구축하였다. 관측유량자료는 수위-내용적-방류량 관계곡선에 의하여 수위변화에 따른 내용적 변화량을 유입량으로 가정하여 환산토록 하였으며, 곡선의 진동이 다소 작고 상태가 양호한 3개 강우사상을 대상으로 분석하였다. 대상유역의 2개 강우관측소(복룡, 반포)의 강우량을 IDW 방법에 의해 공간분포시켜 적용하였으며, 모형의 분석결과, 결정계수($R^2$)는 평균0.88, 용적보존지수(VCI)는 평균 0.14, 첨두유량의 상대오차 ($EQ_p$)는 평균 $0.11m^3/s$로 분석되었다.