• 한국물환경학회지
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• 제24권1호
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• pp.7-18
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• 2008

The objective of this study was to develop and apply a water quality simulation model for the evaluation of ungaged watershed. The Modified WASP5 consisted of three sub-models, LOAD-M, DYN-M, and EUT-M. LOAD-M, an empirical model, estimates runoff loadings using point and non-point source data of villages. Daecheong Dam watershed was selected for the research to calibrate, verify and application of Modified-WASP5. LOAD-M model was established using field data collected from all items of water quality and water quantity gaging stations of the watersheds, and was applied to the ungauged watersheds, taking the watershed properties under consideration. The result of water quality simulation using ModifiedWASP5 shows that the observed BOD data of Yongpo and Daechong Dam in 1999 were 0.8 mg/L and 1.0 mg/L, and simulated data were 0.9 mg/L and 0.9 mg/L, respectively. In case of 1999, average BOD concentrations were 0.8 mg/L and 1.0 mg/L. Simulated concentration showed 1.1 mg/L and 1.5 mg/L, respectively. Generally, the simulation results were in good agreement with the observed data. This study was focused on formulating an integrated model for evaluating ungauged watersheds. Even though simulation results varied slightly due to limited availability of data, the model developed in this study would be a useful tool for the assessment and management of ungauged watersheds.

• 한국농공학회지
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• 제44권5호
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• pp.96-105
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• 2002

As an useful water purification system for non-point source pollution in rural watersheds, interests in constructed wetlands are growing at home and abroad. It is well known that constructed wetlands are easily installed, no special managemental needs, and more flexible at fluctuating influent loads. They have a capacity for purification against nutrient materials such as phosphorus and nitrogen causing eutrophication of lentic water bodies. The Constructed Wetland Design Model (CWDM), developed through this study is consisted mainly of Database System, Runoff-discharge Prediction Submodel, Water Quality Prediction Submodel, and Area Assessment Submodel. The Database System includes data of watershed, discharge, water quality, pollution source, and design factors for the constructed wetland. It supplies data when predicting water quality and calculating the required areas of constructed wetlands. For the assessment of design flow, the GWLF (Generalized Watershed Loading Function) is used, and for water quality prediction in streams estimating influent pollutant load, Water Quality Prediction Submodel, that is a submodel of DSS-WQMRA model developed by previous works is amended. The calculation of the required areas of constructed wetlands is achieved using effluent target concentrations and area calculation equations that developed from the monitoring results in the United States. The CWDM is applied to Bokha watershed to appraise its application by assessing design flow and predicting water quality. Its application is performed through two calculations: one is to achieve each target effluent concentrations of BOD, SS, T-N and T-P, the other is to achieve overall target effluent concentrations. To prove the validity of the model, a comparison of unit removal rates between the calculated one from this study and the monitoring result from existing wetlands in Korea, Japan and United States was made. As a result, the CWDM could be very useful design tool for the constructed wetland in rural watersheds and for the non-point source pollution management.

• 한국농공학회논문집
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• 제57권5호
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• pp.1-12
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• 2015

The study aimed to project inflows and demmands for the agricultural reservoir watersheds in South Korea considering a variety of regional characteristics and the uncertainty of future climate information. The study bias-corrected and spatially downscaled retrospective daily Global Climate Model (GCM) outputs under Representative Concentration Pathways (RCP) 4.5 and 8.5 emission scenarios using non-parametric quantile mapping method to force Soil and Water Assessment Tool (SWAT) model. Using the historical simulation, the skills of un-calibrated SWAT model (without calibration process) was evaluated for 5 reservoir watersheds (selected as well-monitored representatives). The study then, evaluated the performance of 9 GCMs in reproducing historical upstream inflow and irrigation demand at the five representative reservoirs. Finally future inflows and demands for 58 watersheds were projected using 9 GCMs projections under the two RCP scenarios. We demonstrated that (1) un-calibrated SWAT model is likely applicable to agricultural watershed, (2) the uncertainty of future climate information from different GCMs is significant, (3) multi-model ensemble (MME) shows comparatively resonable skills in reproducing water balances over the study area. The results of projection under the RCP 4.5 and RCP 8.5 scenario generally showed the increase of inflow by 9.4% and 10.8% and demand by 1.4% and 1.7%, respectively. More importantly, the results for different seasons and reservoirs varied considerably in the impacts of climate change.

• Korean Journal of Hydrosciences
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• 제2권
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• pp.1-12
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• 1991

To estimate the peak discharge from the small rural watersheds, 53 storm events of seven small watersheds from 1972 to 1989 were selected and were analyzed by the multiple regression technique. The peak values by the new prediction method developed in this study were also compared to the real data of Banwol Basins and the estimated peaks of the several watersheds which were analyzed by the Korean engineering companies. These values were also compared to the results from the other method, i.e. the Rational Method, the Kajiyama Method, the Nakayasu Unit Hydrograph companies. Through Method, the Area Routing Method, etc., which are favored by the Korean engineering companies. Through these comparisons, it is proved that the proposed method may be used for day-to-day use without any problem. However, there should be some modifications and improvements as more data are available in the future.

• 한국환경농학회지
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• 제26권1호
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• pp.17-24
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• 2007

본 연구는 농업용 하천의 특성별 관리 그리고 농업 환경 및 농업 정책에 있어서의 기초자료로서 활용하기 위하여, 전국의 농촌유역 319 하천에 대한 농업용수 수질분석자료를 이용하여 요인분석과 군집분석을 5가지 Case로 구분하여 실시하였다. 각 Case별 인자추출의 수는, Case 1과 Case 2는 각각 5개 인자(factor)가 추출되어 전체의 73.0%, 76.2%를 설명할 수 있었고 Case 3은 4개 인자가 추출되어 전체의 72.4%, Case 4와 Case 5는 각각 1개 인자가 추출되어 전체의 52.6%, 51.6%를 설명할 수 있었다. 인자분석의 결과 추출된 인자로서 군집분석을 실시한 결과, Case 1과 2의 경우 4개 군집, Case 3의 경우 5개 군집, Case 4와 5의 경우 3개의 군집으로 유형화되었으나, 5개의 Case중 군집에 의한 수질 항목들의 일반적 경향, 그룹화된 군집 내의 하천의 개수 등에 의하여 Case 4의 경우인 7개의 수질항목으로 분석한 군집분석의 결과인, 3그룹으로 우리나라 농촌유역 하천을 유형화하는 것이 가장 바람직할 것으로 생각되었다. A그룹은 대부분의 하천들이 속하는 유형으로 우리나라의 평균적인 하천, B그룹은 충북과 경기의 일부 하천들이 속하는 유형으로 SS의 농도는 평균적인 경향, 질소와 인의 농도가 일반적인 하천보다는 조금 높은 수준을 보이는 하천들로 유기물의 농도도 높은 경향을 보여 도시인근이나 농촌마을 등 점오염원에 의한 영향을 많이 받는 하천들이었다. C그룹은 강원도의 하천들이 대부분 속하는 유형으로 질소와 인의 농도가 낮으며, 특히 SS가 낮아 상대적으로 수질이 우수한 경향을 보이는 하천들이었다.

• 한국농공학회논문집
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• 제58권6호
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• pp.23-30
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• 2016

Soil loss is an accompanying phenomenon of hydrologic cycle in watersheds. Both rainfall drops and runoff lead to soil particle detachment, the detached soil particles are transported into streams by runoff. Here, a sediment-laden water problem can be issued if soil particles are severely detached and transported into stream in the watershed. There is a need to estimate or simulate soil erosion in watersheds so that an adequate plan to manage soil erosion can be established. Universal Soil Loss Equation (USLE), therefore, was developed and modified by many researchers for their watersheds, moreover the simple model, USLE, has been employed in many hydrologic models for soil erosion simulations. While the USLE has been applied even in South-Korea, the model is often regarded as being limited in applications for the watersheds in South-Korea since monthly conditions against soil erosion on soil surface are not capable to represent. Thus, the monthly USLE factors against soil erosion, soil erodibility and crop management factors, were established for four major watersheds, which are Daecheong-dam, Soyang-dam, Juam-dam, and Imha-dam watersheds. The monthly factors were established by recent fifteen years from 2000 to 2015. Five crops were selected for the monthly crop management factor establishments. Soil loss estimations with the modified factors were compared to conventional approach that is average annual estimations. The differences ranged from 9.3 % (Juam-dam watershed) to 28.1 % (Daecheong-dam watershed), since the conventional approaches were not capable of seasonally and regionally different conditions.

• 한국농공학회:학술대회논문집
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• 한국농공학회 2002년도 학술발표회 발표논문집
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• pp.449-452
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• 2002

Characteristics of pollutant load during irrigation and non-irrigation periods was investigated for streamwater from a rural watershed. Water was sampled and discharge was measured at 5-days intervals at outlet of study area. The mean concentrations of TN and TP in an irrigation period are higher than in an non-irrigation period, while mean COD concentration in an irrigation period is lower than in a non-irrigation period. For increasing discharge during an irrigation period, TN concentration increase, TP concentration is nearly unchanged, and COD concentrations decreases.

• 한국물환경학회지
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• 제36권5호
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• pp.405-422
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• 2020

Land use change by urbanization has significantly affected the hydrological process including the runoff characteristics. Due to this situation, it has been becoming more complicated to manage non-point source pollutions caused by rainfall. In order to effectively control non-point sources, it is necessary to identify the reduction efficiency of the various management method based on land use characteristics. Thus, the purpose of this study is to analyze the reduction efficiency of non-point source pollution management practices targeting three different watersheds with the different land use characteristics using the Soil and Water Assessment Tool (SWAT). To do this, the vulnerable subwatersheds to non-point source pollution occurrence within each watershed were selected based on the streamflow and water quality simulation results. Then, considering the land use, low impact development (LID) or best management practices (BMPs) were applied to the selected subwatersheds and the efficiency of each management was analyzed. As a result of analysis of the non-point source pollution reduction efficiency, when LID was applied to urban areas, the average reduction efficiencies of SS, NO₃-N, and TP were 5.92%, 4.62%, and 10.35%, respectively. When BMPs were applied to rural areas, the average reduction efficiencies of SS, TN and TP were 35.45%, 4.37%, and 10.16%, respectively. The results of this study can be used as a reference for determining appropriate management methods for non-point source pollution in urban, rural, and complex watersheds.

• 한국농공학회지
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• 제32권E호
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• pp.33-46
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• 1990

Abstract Over 700/0 of the rural land area in Korea is mountainous and small watersheds provide most of the water resources for agricutural use. To provide an appropriate tool for the agricultural water resource development project, SNUA2, a mathematical model for simulating the physical processes governing the precipitation-runoff relationships and predicting the storm and long-term runoff quantities from the small mountainous watersheds was developed. The hydrological characteristics of small mountainous watersheds were reviewed to select appropriate theories for the simulation of the runoff processes, and a deterministic and distributed model was developed. In this, subsurface flows are routed by solving Richard's two dimensional equation, the dynamics of soil moisture contents are simulated by the consideration of phenological factors of canopy plants and surface flows are routed by solving the kinematic wave theory by numerical analysis. As a result of an application test of the model to the Sanglim watershed, peak flow rates of storm runoff were over-estimated by up to 184.2%. The occurence time of peak flow and total runoff volume of storm runoffs simulated were consistent with observed values and the annual runoff volumes were simulated in the error range of less than 5.8%.

• 한국농공학회논문집
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• 제49권6호
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• pp.3-9
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• 2007

Stream flow and water quality were measured and analyzed with respect to flow-weighted mean concentrations (FWMCs) of 21 rainfall events from a forested watershed (Forest Research Watershed: FRW) and two mixed watersheds of agriculture and forest (YuPo-Ri Watershed: YPW and WolGog-ri Watershed: WGW) located in the middle of the North Han River basin. The monitoring of each watershed was one year and conducted between 2004 and 2006. YPW showed more intensive agricultural practices than WGW where traditional practices were common. The average of the 21 FWMCs were in the order of YPF>WGW>FRW and were significantly different from each other at the level of 0.05. It was shown that the land use with intensive agricultural practices produced and discharged more NPS pollutants than that with traditional practices and forest. Specially, SS concentrations from the mixed watersheds were significantly higher than those from FRW. Influencing factors on runoff were analyzed rainfall and watershed area. And rainfall intensity was greater impact on runoff than daily rainfall. Measured water quality indices were shown positive correlations among them in general. However, no significant correlation was shown between COD and nutrients(T-N and T-P).