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RISS 인기검색어
- 검색키워드
- 저자 : 유지수(Yu, Ji Soo) (검색결과 78 건)
- 무료
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SWAT-CUP을 이용한 SWAT 모형 검·보정 II: 모의 실행 및 반복 횟수에 따른 불확실성 분석
유지수,노준우,조영현,Yu, Jisoo,Noh, Joonwoo,Cho, Younghyun 한국수자원학회 2020 한국수자원학회논문집 Vol.53 No.5
The main objective of the study is to propose the most efficient SWAT model calibration method using SWAT-CUP with less computing time and high performance. In order to achieve the goal, Case1-3 (250, 500, and 1,000 simulation runs) and Case4 (1,000 simulation runs in the first iteration and then 500 simulation runs for the following iterations) were defined to compare the results. When evaluating the values of the objective function, Case2 and Case3 reached the same value after the fourth iteration, and Case1 reached the closed value of Case2-3 after the eighth iteration. However, the final estimates of the parameters had different ranges in Cases1-3, and only the results of Case3 and Case4 converged similarly. Thus, it can be considered that the parameter calibration results are highly affected by the initial number of simulation runs. On the other hand, SWAT simulation results did not show the significant difference after the first iteration, unlike the parameter ranges. From the analysis results, we can conclude that the most suitable and effective method was to repeat one or two times of iterations with a sufficient number of simulation runs, as in Case4.
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SWAT-CUP을 이용한 SWAT 모형 검·보정 I: 목적함수에 따른 불확실성 분석
유지수,노준우,조영현,Yu, Jisoo,Noh, Joonwoo,Cho, Younghyun 한국수자원학회 2020 한국수자원학회논문집 Vol.53 No.1
This study aims to quantify the uncertainty that can be induced by the objective function when calibrating SWAT parameters using SWAT-CUP. SWAT model was constructed to estimate runoff in Naesenong-cheon, which is the one of mid-watershed in Nakdong River basin, and then automatic calibration was performed using eight objective functions (R<sup>2</sup>, bR<sup>2</sup>, NS, MNS, KGE, PBIAS, RSR, and SSQR). The optimum parameter sets obtained from each objective function showed different ranges, and thus the corresponding hydrologic characteristics of simulated data were also derived differently. This is because each objective function is sensitive to specific hydrologic signatures and evaluates model performance in an unique way. In other words, one objective function might be sensitive to the residual of the extreme value, so that well produce the peak value, whereas ignores the average or low flow residuals. Therefore, the hydrological similarity between the simulated and measured values was evaluated in order to select the optimum objective function. The hydrologic signatures, which include not only the magnitude, but also the ratio of the inclining and declining time in hydrograph, were defined to consider the timing of the flow occurrence, the response of watershed, and the increasing and decreasing trend. The results of evaluation were quantified by scoring method, and hence the optimal objective functions for SWAT parameter calibration were determined as MNS (342.48) and SSQR (346.45) with the highest total scores.
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코플라 함수를 활용한 이변량 가뭄빈도해석을 통한 우리나라 가뭄 위험도 산정
유지수,유지영,이주헌,김태웅,Yu, Ji Soo,Yoo, Ji Young,Lee, Joo-Heon,Kim, Tea-Woong 한국수자원학회 2016 한국수자원학회논문집 Vol.49 No.3
The drought is generally characterized by duration and severity, thus it is required to conduct the bivariate frequency analysis simultaneously considering the drought duration and severity. However, since a bivariate joint probability distribution function (JPDF) has a 3-dimensional space, it is difficult to interpret the results in practice. In order to suggest the technical solution, this study employed copula functions to estimate an JPDF, then developed conditional JPDFs on various drought durations and estimated the critical severity corresponding to non-exceedance probability. Based on the historical severe drought events, the hydrologic risks were investigated for various extreme droughts with 95% non-exceedance probability. For the drought events with 10-month duration, the most hazardous areas were decided to Gwangju, Inje, and Uljin, which have 1.3-2.0 times higher drought occurrence probabilities compared with the national average. In addition, it was observed that southern regions were much higher drought prone areas than northern and central areas.
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점근유출곡선지수법을 이용한 소유역 유출곡선지수 산정 및 최적 초기손실률 결정
유지수,박동혁,안재현,김태웅,Yu, Ji Soo,Park, Dong-Hyeok,Ahn, Jae-Hyun,Kim, Tae-Woong 한국수자원학회 2017 한국수자원학회논문집 Vol.50 No.11
Two main parameters of NRCS-CN method are curve numbers and intial loss ratio. They are generally selected according to the guideline of US National Engineering Handbook, however, they might cause errors on estimated runoff in Korea because there are differences between soil types and hydrological characteristics of Korean watersheds and those of United States. In this study, applying asymptotic CN regression method, we suggested eight modified NRCS-CN models to decide optimum runoff estimation model for Korean watersheds. RSR (RMSE-observations standard deviation ratio) and NSE (Nash-Sutcliffe efficiency) were used to evaluate model performance, consequently M6 for gauged basins (Avg. RSR was 0.76, Avg. NSE was 0.39) and M7 for ungauged basins (Avg. RSR was 0.82, Avg. NSE was 0.31) were selected. Furthermore it was observed that initial loss ratios ranging from 0.01 to 0.10 were more adequate than the fixed ${\lambda}=0.20$ in most of basins.
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