• Water for future
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• v.17 no.2
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• pp.125-131
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• 1984

watershed Model by mathematical formulation is one of the powerful tool to analyze the hydrologic process in a watershed. The seasonal watershed model is one of the mathematial model from which the monthly streamflow can be simulated and forcasted for given precipitaion data. This model also enables us to compute the monthly runoff at each subbgasin when the basin is subdivided into several small subbasins. The computation of runoff volume makes a Prediction of the areal distirbution of runoff volume for a given precipitation data. Several basins in Han River basin were chosen to simulate the monthly runoff and compute the runoff at each subbasin. A simple logarithmic regression were conducted between runoff ratio and area ratio. The correlation was very high and the equation can be used for prediciting flood volume when flood at downstream gaging station is know.

• Journal of Environmental Science International
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• v.22 no.5
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• pp.523-531
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• 2013

In this study, a method of simulating ephemeral stream runoff characteristics in Jeju watershed is newly suggested. The process based conceptual-physical scheme is established based on the SWAT-K and applied to Cheonmi-cheon watershed which shows the typical pattern of ephemeral stream runoff characteristics. For the proper simulation of this runoff, the intermediate flow and baseflow are controlled to make downward percolation should be dominant. The result showed that surface runoff simulated by using the modified scheme showed good agreement with observed runoff data. In addition, it was found that the estimated runoff directly affected the groundwater recharge rate. This conceptual model should be continuously progressed including rainfall interception, spatially estimated evapotranspiration and so forth for the reasonable simulation of the hydrologic characteristics in Jeju island.

• Magazine of the Korean Society of Agricultural Engineers
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• v.37 no.5
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• pp.35-42
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• 1995

his paper is to develop a GIS application model (GISCELWAB) for the spatial simulation of surface runoff from a small watershed. The model was constituted by three submodels : The input data extraction model (GISINDATA) which prepares cell-based input data automatically for a given watershed, the cell water balance model (CELWAB) which calculates the water balance for a cell and simulates surface runoff of watershed simultaneously by the interaction of cells, and the output data management model (GISOUTDISP) which visualize the results of temporal and spatial variation of surface runoff. The input data extraction model was developed to solve the time-consuming problems for the input-data preparation of distributed hydrologic model. The input data for CELWAB can be obtained by extracting ASCII data from a vector map. The output data management model was developed to convert the storage depth and discharge of cells into grid map. This model enables to visualize the spatial formulation process of watershed storage depth and surface runoff wholly with time increment.

• Magazine of the Korean Society of Agricultural Engineers
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• v.37 no.3_4
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• pp.23-33
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• 1995

Geographic data which are difficult to handle by the characteristics of spatial variation and variety turned into a possibility to analyze with tlie computer-aided digital map and the use of Geographic Information System(GIS). The purpose of this study is to develop and apply a GIS application model (GISCELWAB) for the spatial simulation of surface runoff from a small watershed. This paper discribes the modeling procedure and the applicability of the cell water balance model (CELWAB) which calculates the water balance of a cell and simulates surface runoff of watershed simultaneously by the interaction of cells. The cell water balance model was developed to simulate the temporal and spatial storage depth and surface runoff of a watershed. The CELWAB model was constituted by Inflow-Outflow Calculator (JOC) which was developed to connect cell-to-cell transport mechanism automatically in this study. The CELWAB model requests detail data for each component of a cell hydrologic process. In this study, therefore, BANWOL watershed which have available field data was selected, and sensitivity for several model parameters was analyzed. The simulated results of surface runoff agreed well with the observed data for the rising phase of hydrograph except the recession phase. Each mean of relative errors for peak discharge and peak time was 0.21% and2.1 1% respectively. In sensitivity analysis of CELWAB , antecedent soil moisture condition(AMC) affected most largely the model.

• Magazine of the Korean Society of Agricultural Engineers
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• v.29 no.2
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• pp.53-63
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• 1987

Due to their wide range of application, deterministic comprehensive hydrologic models using digital computers have been developed in all countries of the world and researches are being undertaken for their appropriate applications. The aim of this study has been to demonstrate the practical implementation of a physically based distributed hydrologic model, the USDAHL-74 model and to investigate its ability to simulate the long term estimate of water balance quantities in a Korean mountainous watershed. Application of the model to Dochuk watershed indicates the following results. 1.Since the USDAHL-74 model includes all the major components of the hydrologic cycle in agricultural watersheds, thus is comprehnsive, the model seems to have a wide range of application from the fact that simulation results obtained are not only runoff volumes m various time units but their spatial variation as well as even soil moisture within the watershed. 2.An approximate calibration to determine the parameter values in the model using various data obtained from D0chuk shed shows that the simulation error of yearly runoff volume is only 0.6 % and a correlation coefficient between observed daily runoff volume and simulated one is 0.91 in all calibrated period.3.As a verification test of the model, runoff volumes are simulated using 1986 year data without changing the parameter values determined by 1985 year data. The tests show that the USDAHL-74 model is a flexible tool and that realistic production to simulate the long term estimate of runoff in Korean mountainous watershed could be obtained using only a short period of calibration.4. Despite of the encouraging results, there still remain minor problems concerning the practical application of the model to improve the result of simulations. Some of these are the small descrepancies between observed and simulated daily runoff volume appeared in the vicinity of peaks and the recession of1 the daily hydrographs and the model performance for the frozen ground and melting process in the model. 5. Alough the use of parameter with physical significance and the ability to improve calibrations on the basis of physical reasoning represents advantages in the simulation for ungaged watersheds, further researches are needed to use the USDAHL-74 mode to simulate runoff in ungaged watersheds.

• Journal of Environmental Science International
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• v.25 no.1
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• pp.31-40
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• 2016

The purpose of this study was to analyse the runoff characteristics of non-point pollution sources in an urban watershed and determine the effectiveness of newly installed riverwater treatment system to reduce water pollution caused by storm runoff in the urban watershed. The results of this study showed that the levels of BOD5 and suspended solid were highly influenced by first-flush effect and the pollutant load of those two parameters were also very high in the urban watershed. Meanwhile, the effectiveness of riverwater treatment system to reduce the levels of BOD5 and suspended solid was relatively high, but those to reduce the levels of T-N and T-P was low, which needs some additional unit treatment process such as filtration and coagulation. Nonetheless, the riverwater treatment system tested was relatively simple in installation and operation, effective in removing many water pollutants and, most importantly, does not require much space as other treatment systems, so it could be an attractive alternative option to reduce riverwater pollution caused by storm runoff in urban watersheds.

• Journal of Environmental Impact Assessment
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• v.15 no.6
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• pp.435-441
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• 2006

For the calibration of rainfall-runoff model, automatic calibration methods are used instead of manual calibration to obtain the reliable modeling results. When mathematical programming techniques such as linear programming and nonlinear programming are applied, there is a possibility to arrive at the local optimum. To solve this problem, genetic algorithm is introduced in this study. It is very simple and easy to understand but also applicable to any complicated mathematical problem, and it can find out the global optimum solution effectively. The objective of this study is to develope a parameter optimization program that integrate a genetic algorithm and a rainfall-runoff model. The program can calibrate the various parameters related to the runoff process automatically. As a rainfall-runoff model, SWMM is applied. The automatic calibration program developed in this study is applied to the Jangcheon watershed flowing into the Youngrang Lake that is in the eutrophic state. Runoff surveys were carried out for two storm events on the Jangcheon watershed. The peak flow and runoff volume estimated by the calibrated model with the survey data shows good agreement with the observed values.

• Journal of Korean Society on Water Environment
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• v.26 no.1
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• pp.61-70
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• 2010

The increase of impervious cover (IC) in a watershed is known as an important factor causing alteration of water cycle, deterioration of water quality and biological communities of urban streams. The study objective was to assess the impact of IC changes on the surface runoff characteristics of Kap Stream basin located in Geum river basin (Korea) using the Storm Water Management Model (SWMM). SWMM was calibrated and verified using the flow data observed at outlet of the watershed with 8 days interval in 2007 and 2008. According to the analysis of Landsat satellite imagery data every 5 years from 1975 to 2000, the IC of the watershed has linearly increased from 4.9% to 10.5% during last 25 years. The validated model was applied to simulate the runoff flow rates from the watershed with different IC rates every five years using the climate forcing data of 2007 and 2008. The simulation results indicated that the increase of IC area in the watershed has resulted in the increase of peak runoff and reduction of travel time during flood events. The flood flow ($Q_{95}$) and normal flow ($Q_{180}$) rates of Kap Stream increased with the IC rate. However, the low flow ($Q_{275}$) and drought flow ($Q_{355}$) rates showed no significant difference. Thus the subsurface flow simulation algorithm of the model needs to be revisited for better assessment of the impact of impervious cover on the long-term runoff process.

• Journal of Korean Society on Water Environment
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• v.27 no.5
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• pp.587-596
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• 2011

The interest in hydrological modeling has increased significantly recently due to the necessity of watershed management, specifically in regards to lumped models, which are being prosperously utilized because of their relatively uncomplicated algorithms which require less simulation time. However, lumped models require empirical coefficients for hydrological analyses, which do not take into consideration the heterogeneity of site-specific characteristics. To overcome such obstacles, a distributed model was offered as an alternative and the number of researches related to watershed management and distributed models has been steadily increasing in the recent years. Thus, in this study, the feasibility of a grid-based rainfall-runoff model was reviewed using the flood runoff process in the Han River basin, including the ChungjuDam, HoengseongDam and SoyangDam watersheds. Hydrological parameters based on GIS/RS were extracted from basic GIS data such as DEM, land cover, soil map and rainfall depth. The accuracy of the runoff analysis for the model application was evaluated using EFF, NRMSE and QER. The calculation results showed that there was a good agreement with the observed data. Besides the ungauged spatial characteristics in the SoyangDam watershed, EFF showed a good result of 0.859.

• Journal of Korean Society of Forest Science
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• v.89 no.5
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• pp.564-575
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• 2000

This study was carried out to reveal characteristics of long-term runoff by using HYCYMODEL in a small forested watershed. From May to September in 1998 and in 1999, the fitness of HYCYMODEL and runoff characteristics were estimated by HYCYMODEL using rainfall and discharge at the experimental watershed. The function of stage and discharge in the experimental watershed was determined as following equation $Q=11.148H^{2.5867}$($R^2=0.9956$). From May to September in 1998 and in 1999, the runoff rates were 57.7% in 1998 and 87.1% in 1999 at the experimental watershed. The discharge was assumed to be increased because of rainfall intensity difference and thinning. By applicability test, the HYCYMODEL showed good estimation of runoff by optimized fifteen parameters. Comparing runoff characteristics before and after thinning by calculating through HYCYMODEL, direct runoff and base runoff increased 4%, 7%, respectively as evapotranspiration decreased 11%. Parameters $D_{50}$ and $K_h$, which were related to the direct run, and a parameter $K_u$, which was related to the baseflow, were assumed to indicate that forest was changed by the effect of thinning and weathering process of bed rock.