• Economic and Environmental Geology
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• v.41 no.4
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• pp.443-451
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• 2008

Memon(1995) pointed out that the groundwater recharge from the precipitation is affected by various factors such as the occurrence, intensity, duration, and seasonal distribution of rainfall; air temperature, humidity, and wind velocity; the character and thickness of the soil layer above the water table; vegetated cover, soil moisture content, depth to the water table, topography; and land use. To reflect above factors, groundwater recharge in Chungju basin is computed by using the SWAT-K which is a longterm continuous watershed hydrologic model. Frequency analysis is adopted to evaluate the existing values of potential amount of groundwater development which is made by the 10 year drought frequency rainfall multiplied by recharge coefficient. In this work, the recharge rates of 10 year drought frequency in subbains were computed and compared with the existing values of potential amount of groundwater development. This process could point out the problems of existing precesses used for computing potential amount of groundwater development.

• Journal of Korea Water Resources Association
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• v.40 no.5
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• pp.419-430
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• 2007

Integrated modelling of surface water and groundwater has become important to satisfy the growing demands for sustainable water resources and improved water quality. In this study, the integrated model of the semi-distributed watershed model, SWA T and the fully-distributed groundwater flow model, MODFLOW is applied to Musirn river basin for the purpose of investigating its applicability to reproduce watershed-scale hydrological processes. This objective is accomplished by first demonstrating good agreement between the simulated discharge hydrographs with the measured hydrographs for the period of 2001 -2004 while simultaneously calibrating the calculated groundwater level distribution to observation wells. Next, the integrated model is used to evaluate the effect of different temporal precipitation averages on hydrodynamic processes of streamflow, percolation, recharge and groundwater discharge. Moreover, comprehensive simulations are performed to present the relationships between monthly precipitation and each hydrological component, and to analyze the temporal-spatial variability of recharge. The results show that the components are highly interrelated, and that the heterogeneity of watershed characteristics such as subbasin slope, land use, soil type causes a significant spatial variation of recharge. Overall it is concluded that the model is capable of reproducing the temporally and spatially varied surface and subsurface hydrological processes at the watershed scale.

• Journal of the Korean Association of Geographic Information Studies
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• v.14 no.2
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• pp.28-39
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• 2011

This study estimates the characteristics of flow loads by classification items of the Ministry of Environment and by land cover change using HyGIS-SWAT. The result of analyzing the land cover change using the classification items shows that the urban area and the farmland area in Mishim-cheon and Gap-cheon are expanding while the forest area is decreasing. The result of analyzing the characteristics of classification items shows that peak discharge increases and total yearly discharge decreases in Mushim-cheon. The result of analyzing the characteristics by data-construction period shows that peak discharge decreases but total discharge increases in Gap-cheon. Three land cover change scenarios are applicable to the expansion of urban area and farmland area. According to the result of application, urbanization influences and Farmland area expansion influences increase peak discharge, total yearly discharge and sediment concentration.

• Journal of Korea Water Resources Association
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• v.49 no.11
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• pp.951-959
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• 2016

This study was conducted to evaluate observed runoff data collected every 10 minutes at stream gauging stations in Jeju Island using a physically-based model, SWAT. The Hancheon watershed was selected as study area, and ephemeral stream algorithm suggested by previous research was incorporated into the model, which is able to simulate ephemeral runoff pattern of Jeju streams. Simulated runoff and runoff rates were compared to observations during 2008-2013, which showed 'very good' performance rating in Nash-Sutcliffe model efficiency (ME) and determination coefficient ($R^2$). Some observations had problems such that runoff rates were very high for some rainfall events with little amount of antecedent rainfall, and were very low or missing with much rainfall comparing to previous researches. Additionally, regression equation between precipitation and simulated runoff was generated with high degree of correlation. The equation can be utilized to simply predict reasonable runoff, or to investigate and complement the abnormal or missing data of observations on the assumption that modelling results were sufficiently reliable and satisfactory. As results, minimizing the error in calibrating the model by evaluation of observed data would be helpful to accurately model the rainfall-runoff characteristics and analyze the water balance components of watersheds in Jeju Island.

• Journal of Korea Water Resources Association
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• v.39 no.11 s.172
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• pp.947-960
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• 2006

This study shows the application of sustainable water resource planning procedure developed in the previous paper. Its goal is to prevent the streamflow depletion in upstream watershed of the Anyangcheon which is a typical urban stream. The pressure-state-response model which is the framework to reflect the sustainability was applied. The composite programming which is the multilevel multicriteria decision making technique is also used in the calculation of state and evaluation index. The feasible alternatives were proposed and hydrologically analyzed by SWAT(Soil and Water Assessment Tool) and the priority ranking of alternatives were proposed based on the results of SWAT.

• Journal of Environmental Impact Assessment
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• v.20 no.1
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• pp.25-36
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• 2011

In this study, the accurate water quality analysis in rivers, including the non-point source is performed. First of all, watershed model, SWAT(Soil and Water Assessment Tool) was applied to analyze the impact of the non-point source in study area. And then, water quality analysis integrating the point source and the non-point source is implemented using QUALKO model. For more exact simulation, it should be the calibration and verification of variables and parameters which are needed for simulation. In addition, the importance of considering the non-point source was confirmed in river water quality simulation. BOD, TN, TP were analysed, and the results shows that BOD, TN and TP concentration was increased to 16.8%, 8.2% and 25.8% respectively. The more accurate estimate will be carried if use of reliable measurements and watershed simulation be done in models linking process. The suggested technique will improve the accuracy of the water quality analysis. The methodologies presented in this study will contribute to basin-wide water quantity and quality management.

• Journal of Environmental Science International
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• v.23 no.4
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• pp.723-735
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• 2014

Sediment discharge by long-term runoff in the Nakdong River watershed should be predicted for the maintenance and management of the Nakdong River newly changed by the four major river restoration project. The data establishment by the analysis of runoff and sediment discharge using the long-term watershed model is necessary to predict possible problems by incoming sediments and to prepare countermeasures for the maintenance and management. Therefore, sediment discharges by long-term runoff in the main points of the Nakdong River were calculated using SWAT(soil and water assessment tool) model and the relations and features between rainfall, runoff, and sediment discharge were analyzed in this study. As a result of sediment discharge calculation in the main points of the Nakdong River and tributaries, the sediment discharge at the outlet of the Naesung Stream was greater than the Jindong Station in the Lower Nakdong River from 1999 to 2008 except the years with low precipitation. The sediment discharge at the Nakdong River Estuary Barrage (NREB) was corresponding to 20% of the Jindong Station which is located about 80 km upstream from NREB.

• Economic and Environmental Geology
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• v.44 no.5
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• pp.433-442
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• 2011

In Korea, groundwater management has been conducted based on the estimation of annual average of groundwater recharge. Since groundwater recharge and surface water-groundwater interactions show spatiotemporal variation, continuous monitoring and dynamic analysis must be carried out to evaluate the sustainability of groundwater resources. In this study, SWAT-MODFLOW, an integrated surface water-groundwater model was used to analyze surface-groundwater interactions for various groundwater pumping scenarios in Musimcheon watershed. When current usage is applied, the baseflow reduction is about 16%, and annual averaged storage reduction is about 27 mm for whole watershed. As a holistic approach to groundwater sustainability considers the hydrological, ecological, socioeconomic, technological aspects of groundwater utilization, the exploitable groundwater should be determined by physical analysis as well as social compromise in a community.

• Journal of Korean Society on Water Environment
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• v.31 no.5
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• pp.482-490
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• 2015

In this study, considering the factors that affects sediment trapping efficiency of Vegetative Filter Strips (VFS), the scenarios were designed to develop a regression equation to estimate sediment trapping efficiency of VFS for agricultural fields in South-Korea. For this, general conditions of agricultural fields in South-Korea were investigated. Then, based on these results, total 53,460 scenarios were set and simulated by Vegetative Filter Strip MODel (VFSMOD-w). Two variables were determined from the results of 53,460 scenarios. These two variables were applied to CurveExpert for development of a equation, which can estimate sediment trapping efficiency of VFS. The equation developed in this study can be used in SWAT model for estimation of sediment reduction efficiency of VFS to upland field in Korea. Moreover, it is expected that VFS will be effectively applied to agricultural fields in South-Korea.

• Journal of Korea Water Resources Association
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• v.42 no.11
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• pp.921-931
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• 2009

For the assessment of climate change impacts for the Byeongseong stream, CGCM 3.1 T63 is selected as future climate information. The projections come from CGCM used to simulate the GHG emission scenario known as A2. Air temperature and precipitation information from the GCM simulations are converted to regional scale data using the statistical downscaling method known as MSPG. Downscaled climate data from GCM are then used as the input data for the SWAT model to generate regional runoff and water quality estimates in the Byeongseong stream. As a result of simple sensitivity analysis, the increase of CO2 concentration leads to increase water yield through reduction of evapotranspiration and increase of soil water. Hydrologic responses to climate change are in phase with precipitation change. Climate change is expected to reduce water yields in the period of 2021-2030. In the period of 2051-2060, stream flow is expected to be reduced in spring season and increased in summer season. While soil losses are also in phase with water yields, nutrient discharges (i.e., total nitrogen) are not always in phase with precipitation change. However, it should be noted that there are a lot of uncertainties in such multiple-step analysis used to convert climate information from GCM-based future climate projections into hydrologic information.