• 한국물환경학회지
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• 제25권3호
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• pp.351-362
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• 2009

The Soil and Water Assessment Tool (SWAT) model, semi-distributed model, first divides the watershed into multiple subwatersheds, and then extracts the basic computation element, called the Hydrologic Response Unit (HRU). In the process of HRU generation, the spatial information of land use and soil maps within each subwatershed is lost. The SWAT model estimates the HRU topographic data based on the average slope of each subwatershed, and then use this topographic datum for all HRUs within the subwatershed. To improve the SWAT capabilities for various watershed scenarios, the Spatially Distributed-HRU (SD-HRU) pre-processor module was developed in this study to simulate site-specific topographic data. The SD-HRU was applied to the Hae-an watershed, where field slope lengths and slopes are measured for all agricultural fields. The analysis revealed that the SD-HRU pre-processor module needs to be applied in SWAT sediment simulation for accurate analysis of soil erosion and sediment behaviors. If the SD-HRU pre-processor module is not applied in SWAT runs, the other SWAT factors may be over or under estimated, resulting in errors in physical and empirical computation modules although the SWAT estimated flow and sediment values match the measured data reasonably well.

• 한국농림기상학회지
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• 제13권1호
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• pp.20-27
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• 2011

북한지역에 대해 좌표내장 수치기후지도를 제작하기 위한 선결조건으로서 국지 소기후 추정모형의 최소 공간적용단위인 표준유역(Hydrologic Unit)이 설정되어야 한다. Arc Hydro 기반의 유역추출 알고리즘을 ASTER GDEM에 적용하고, 북한의 5대강(예성강, 대동강, 청천강, 압록강, 두만강) 및 산경도에 나타난 산맥체계에 의해 보완함으로써 신뢰성 높은 북한지역 표준유역도를 제작하였다. 이 표준유역도에 의하면 북한지역은 21개의 대권역, 93개의 중권역, 885개의 소유역으로 구성된다. 기존 남한 표준유역도 840개와 결합하고 각각 소기후모형을 적용할 경우 한반도 전역을 1,725개의 소기후구로 하는 상세 농업기후지대구분이 가능해진다.

• 환경영향평가
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• 제18권5호
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• pp.281-291
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• 2009

In Total Water Pollutant Load Management System of Korea, unit load approach based on land register data is currently used for the estimation of non-point pollutant load. However, a problem raised that land register data could not always reflect the actual land surface coverages which determine runoff characteristics of non-point pollution sources. As a way to overcome this, we tried to establish quantitative relationships between the aerial images (0.4m resolution) which reflect actual land surface coverages and the land registration maps according to the 19 major designated land-use categories in Kyeongan watershed. Analyses showed different relationships according to the land-use categories. Only a few land-use categories including forestry, road and river showed essentially identical and some categories such as orchard, parking lot and sport utility site showed no relationships at all between image data and land register data. Except for the two cases, all the other categories showed statistically significant linear relationships between image data and land register data. The analyses indicate that using high resolution aerial maps is a better way to estimate non-point pollutant load. If the aerial maps are not available, application of the linear relationships as conversion factors of land register data to image data could be an possible option to estimate non-point pollutant loads for the specific land-use categories in Kyeongan watershed.

• 한국농공학회논문집
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• 제63권1호
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• pp.103-116
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• 2021

Analysis of runoff is substantial for effective water management in the watershed. Runoff occurs by reaction of a watershed to the rainfall and has non-linearity and uncertainty due to the complex relation of weather and watershed factors. ANN (Artificial Neural Network), which learns from the data, is one of the machine learning technique known as a proper model to interpret non-linear data. The performance of ANN is affected by the ANN's structure, the number of hidden layer nodes, learning rate, and activation function. Especially, the activation function has a role to deliver the information entered and decides the way of making output. Therefore, It is important to apply appropriate activation functions according to the problem to solve. In this paper, ANN models were constructed to estimate runoff with different activation functions and each model was compared and evaluated. Sigmoid, Hyperbolic tangent, ReLU (Rectified Linear Unit), ELU (Exponential Linear Unit) functions were applied to the hidden layer, and Identity, ReLU, Softplus functions applied to the output layer. The statistical parameters including coefficient of determination, NSE (Nash and Sutcliffe Efficiency), NSEln (modified NSE), and PBIAS (Percent BIAS) were utilized to evaluate the ANN models. From the result, applications of Hyperbolic tangent function and ELU function to the hidden layer and Identity function to the output layer show competent performance rather than other functions which demonstrated the function selection in the ANN structure can affect the performance of ANN.

• 한국지리정보학회지
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• 제16권3호
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• pp.68-80
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• 2013

본 연구는 미계측유역의 설계홍수량 산정을 목적으로 영국의 강우-유출모형인 FEH-ReFH(Flood Estimation Handbook-Revitalised Flood Hydrograph)의 국내 적용성을 평가하기 위해 위천유역의 일부인 남천유역($165.12km^2$)을 대상으로 한 강우-유출 모형을 구성하는데 있다. 모형의 입력자료인 유역 및 수문특성인자를 한국 실정에 맞게 구축하기 위해 GIS기반 전처리 프로그램을 개발하였다. 모형은 남천 유역에 대하여 관측된 6개의 강우-유출 사상을 이용한 보정을 실시하여, 모형의 적용 적합성을 분석하였다. 모형의 손실율 및 단위유량도 매개변수를 대상으로 실측자료를 이용한 보정을 실시하였다. 본 연구의 결과는 기존의 설계홍수량 산정과정에 있어, 영국의 방법을 고려한 국내의 표준 설계홍수량 산정과정을 정립하는데 기여할 것으로 판단된다.

• 대한환경공학회지
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• 제38권3호
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• pp.117-127
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• 2016

새만금유역을 대상으로 수질개선을 위한 다양한 방법을 검토하고 환경유지용수 확보에 따른 수질개선 효과를 평가하였다. 만경강과 동진강의 환경유지용수 확보를 위해 강변저류지설치, 저수지증고, 신규댐 건설, 용수 취배수체계 조정, 용담댐, 섬진강댐 물 이용체계를 조정하는 방안을 선정하였다. 환경유지용수 확보 가능한 방안에 따른 시나리오 구성을 통해 수질개선효과를 예측하기 위하여 유역모형 SWAT과 수질모델 QUAL2K를 연계하여 BOD와 T-P항목에 대해 수질변화를 모의하였다. 시나리오 적용을 통한 모의 결과 총량관리단위유역말단인 만경B 지점의 경우 관개기 BOD 수질개선율은 28.70%, T-P의 수질개선율은 17.09%로 나타났고, 비관개기BOD 수질개선율은 28.51%, T-P의 수질개선율은 28.68%로 나타났다. 동진 A 지점의 경우 관개기 BOD 수질개선율은 14.39%, T-P 수질개선율은 14.59%, 비관개기 BOD 수질개선율은 15.54%, T-P 수질 개선율은 19.46 %로 나타나 환경유지용수가 수질개선에 효과가 있는 것으로 분석되었고 특히, 비관개기 수질개선에 효과가 크다는 것을 알 수 있었다.

• 한국방재학회 논문집
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• 제6권1호
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• pp.49-58
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• 2006

본 연구는 미계측이나 자료가 결핍된 유역에서 지리정보시스템을 이용하여 유역의 지형학적 매개변수를 얻어 유도된 지형학적 순간단위유량도에 의한 강우-유출의 특성을 분석하였다. 횡성댐 상류 섬강시험유역에서 얻어진 실측자료를 사용하였고, 직접유출을 분석하기 위하여 가변기울기법을 이용하였다. 아울러 4차 하천유역인 섬강시험유역은 Horton-Strahler의 차수법칙에 따라 일정한 규칙을 가지고 발달한 수계임을 확인하였다. GIUH의 사용에 따른 섬강시험유역의 규모계수 결정식의 변형을 하였고, 유출특성속도는 1.0m/s으로 나타났다. 4차 하천유역인 섬강시험유역의 출구인 매일교수위국과 3차 하천유역의 출구인 소군교와 농거리교수위국에서의 GIUH에 의한 수문곡선은 첨두시간이후의 유역의 저류능에서 약간의 차이를 보이나, 실측값과의 비교에서 잘 일치하였다. 아울러 유역을 보다 세분화하여 적용한 GIUH모형에 의한 수문곡선을 상류유입수문곡선으로 하여 HEC-HMS를 이용하여 수문 추적한 결과가 전체유역을 대상으로 한 GIUH모형에 의한 수문곡선보다 실측치에 잘 일치하였다. 전반적으로 GIUH에 의한 강우-유출해석은 미계측 유역에 사용성이 있는 것으로 평가된다.

• Environmental Engineering Research
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• 제25권3호
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• pp.267-273
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• 2020

This Hydrokinetic energy system is the process of extracting energy from rivers, canals and others sources to generate small scale electrical energy for decentralized usage. This study investigates the application of Soil and Water Assessment Tool (SWAT) in Geographical Information System (GIS) environment to evaluate the theoretical hydrokinetic energy potentials of selected Rivers (Asa, Awun and Oyun) all in Asa watershed, Kwara state, Nigeria. SWAT was interfaced with an open source GIS system to predict the flow and other hydrological parameters of the sub-basins. The model was calibrated and validated using observed stream flow data. Calibrated flow results were used in conjunction with other parameters to compute the theoretical hydrokinetic energy potentials of the Rivers. Results showed a good correlation between the observed flow and the simulated flow, indicated by ash Sutcliffe Efficiency (NSE) and R² of 0.76 and 0.85, respectively for calibration period, and NSE and R² of 0.70 and 0.74, respectively for the validation period. Also, it was observed that highest potential of 154.82 MW was obtained along River Awun while the lowest potential of 41.63 MW was obtained along River Asa. The energy potentials obtained could be harnessed and deployed to the communities around the watershed for their energy needs.

• 한국가시화정보학회지
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• 제19권1호
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• pp.28-35
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• 2021

In this study, an image processing method for the measurement of two-phase bubbly flow is developed. Shadowgraphy images obtained by high-speed camera are used for analysis. Some bubbles are generated as single unit and others are overlapped or clustered. Single bubbles can be easily analyzed using parameters such as bubble shape, centroid, and area. But overlapped bubbles are difficult to transform clustered bubbles into segmented bubbles. Several approaches were proposed for the bubble segmentation such as Hough transform, connection point method and watershed. These methods are not enough for bubble segmentation. In order to obtain the size distribution of bubbles, we present a method of splitting overlapping bubbles using watershed and approximating them to ellipse. There is only 5% error difference between manual and automatic analysis. Furthermore, the error can be reduced down to 1.2% when a correction factor is used. The ellipse fitting algorithm developed in this study can be used to measure bubble parameters accurately by reflecting the shape of the bubbles.

• 물과 미래
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• 제9권2호
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• pp.76-86
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• 1976

The 30-year design flood hydrograph for the Musim Representative Basin, one of the study basins of the International Hydrological Program, is synthesized by the method of unit hydrograph. The theory of unit hydrograph has been well known for a long time. However, the synthesis of flood hydrograph by this method for a basin with insufficient hydrologic data is not an easy task and hence, assumptions and engineering judgement must be exercized. In this paper, the problems often encountered in applying the unit hydrograph method are exposed and solved in detail based on the theory and rational judgement. The probability rainfall for Cheonju Station is transposed to the Musim Basin since it has not been analyzed due to short period of rainfall record. The duration of design rainfall was estimated based on the time of concentration for the watershed. The effective rainfall was determined from the design rainfall using the SCS method which is commonly used for a small basin. The spatial distribution of significant storms was expressed as a dimensionless rainfall mass curve and hence, it was possible to determine the hyetograph of effective design storm. To synthesize the direct runoff hydrograph the 15-min. unit hydrograph was derived by the S-Curve method from the 1-hr unit hydrograph which was obtained from the observed rainfall and runoff data, and then it was applied to the design hyetograph. The exsisting maximum groundwater depletion curve was derived by the base flow seperation. Hence, the design flood hydrograph was obtained by superimposing the groundwater depletion curve to the computed direct runoff hydrograph resulting from the design storm.