• Proceedings of the Korea Water Resources Association Conference
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• 2020.06a
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• pp.101-101
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• 2020

Traditional stochastic simulation of hydroclimatological variables often underestimates the variability and correlation structure of larger timescale due to the difficulty in preserving long-term memory. However, the Long Short-Term Memory (LSTM) model illustrates a remarkable long-term memory from the recursive hidden and cell states. The current study, therefore, employed the LSTM model in stochastic generation of hydrologic and climate variables to examine how much the LSTM model can preserve the long-term memory and overcome the drawbacks of conventional time series models such as autoregressive (AR). A trigonometric function and the Rössler system as well as real case studies for hydrological and climatological variables were tested. Results presented that the LSTM model reproduced the variability and correlation structure of the larger timescale as well as the key statistics of the original time domain better than the AR and other traditional models. The hidden and cell states of the LSTM containing the long-memory and oscillation structure following the observations allows better performance compared to the other tested conventional models. This good representation of the long-term variability can be important in water manager since future water resources planning and management is highly related with this long-term variability.

• Journal of The Korean Society of Agricultural Engineers
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• v.62 no.1
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• pp.39-50
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• 2020

The objective of this study was to assess the livestock nonpoint source pollutant impact on water quality in Namgang dam watershed using the HSPF (Hydrological Simulation Program-Fortran) model. The input data for the HSPF model was established using the landcover, digital elevation, and watershed and river maps. In order to apply the pollutant load to the HSPF model, the delivery load of the livestock nonpoint source in the Namgang dam watershed was calculated and used as a point pollutant input data for the HSPF model. The hydrologic and water quality parameters of HSPF model were calibrated and validated using the observed runoff data from 2007 to 2015 at Sancheong station. The R² (Determination Coefficient), RMSE (Root Mean Square Error), NSE (Nash-Sutcliffe efficiency coefficient), and RMAE (Relative Mean Absolute Error) were used to evaluate the model performance. The simulation results for annual mean runoff showed that R² ranged 0.79~0.81, RMSE 1.91~2.73 mm/day, NSE 0.7~0.71 and RMAE 0.37~0.49 mm/day for daily runoff. The simulation results for annual mean BOD for RMSE ranged 0.99~1.13 mg/L and RMAE 0.49~0.55 mg/L, annual mean TN for RMSE ranged 1.65~1.72 mg/L and RMAE 0.55 mg/L, and annual mean TP for RMSE ranged 0.043~0.055 mg/L and RMAE 0.552~0.570 mg/L. As a result of livestock nonpoint pollutant loading simulation for each sub-watersehd using the HSPF model, the BOD ranged 16.6~163 kg/day, TN ranged 27.5~337 kg/day, TP ranged 1.22~14.1 kg/day.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.24-27
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• 1996

The storage function method(SFM) is one of hydrologic flood routings which has been used most widely in Korea and Japan. This paper presents a storage function method using multiple model adaptive estimation(MMAE), in which a model set is generated by partitioning storage parameters over feasible range, and each storage function model is estimated, and then the weighted average of them is calculated. Finally, the future runoff is predicted in real time by means of observed data of water level at dam and rainfall. Simulation results applied to actual data show that the proposed method has much better performance than that of conventional SFM.

• Journal of The Korean Society of Agricultural Engineers
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• v.55 no.4
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• pp.13-20
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• 2013

The purpose of this study was to evaluate the applicability of the HSPEXP expert system for the calibration of the Hydrological Simulation Program - Fortran (HSPF) for the study watershed. HSPEXP offers advice to the modeler, suggesting parameter changes that might result in better representation of a river basin and provides explanations supporting the recommended parameter changes. The study watershed, Sancheong, is located within the Nakdong River Basin and having the size of $1,072.4km^2$. Input data for the HSPF model were obtained from the landuse map, digital elevation map, meteorological data and others. Water flow data from 2006 to 2008 were used for calibration and from 2009 to 2010 were for validation. Using the HSPEXP expert system, hydrological parameters were adjusted based on total volume, then low flows, storm flows, and finally seasonal flows. For the calibration and validation period, all the HSPEXP model performance criteria were satisfied.

• Journal of Korea Water Resources Association
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• v.39 no.8 s.169
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• pp.703-716
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• 2006

The flow duration curves in the present and the ideal hydrologic cycle were derived using SWAT model. The present situation is the landuse and the groundwater withdrawal in the year of 2000 and the ideal situation is the landuse of 1975 and no groundwater withdrawal. These results were compared with the previous instream flow requirements which are the larger flow between the average drought flow and environmental control flow. As a result, the present and ideal drought flows of Ojeoncheon, Hakuicheon, Samseongcheon, and Sammakcheon, were the same and the drought flows of Samseongcheon and Sammakcheon were even zero since the baseflow is very little due to the small and mountainous watersheds. The previous instream flow requirement for the riverine function is also larger than the low flow of the ideal hydrologic cycle. The present method to set the instream flow requirement is not proper for the small mountainous watershed since it can be usually overestimated and drive the artificial measures to secure the streamflow Therefore, another method should be developed such as the low flow and the average flow between the drought flow and the low flow of the ideal hydrologic cycle using the proper hydrologic simulation model such as SWAT which can consider the landuse.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.5
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• pp.1334-1343
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• 2008

Growing needs for efficient management of water resources urge the joint operation of dams and integrated management of whole basin. As one of the tools for supporting above tasks, this study aims to constitute a hydrologic model that can simulate the streamflow discharges at some control points located both upper and down stream of dams. One of the currently available models is being studied to be applied with a least effort in order to support the ongoing project of KWATER (Korea Water Resources Corporation), "Establishment of integrated operation scheme for the dams in Han River Basin". On this study, following works have been carried out : division of Han River Basin into 24 sub-basins, use of rainfall data of 151 stations to make spatial distribution of rainfall, selection of control points such as Soyanggang Dam, Chungju Dam, Chungju Release Control Dam, Heongseong Dam, Hwachun Dam, Chuncheon Dam, Uiam Dam, Cheongpyung Dam and Paldang Dam, selection of SSARR (Streamflow Synthesis and Reservoir Regulation) model as a hydrologic model, preparation of input data of SSARR model, sensitivity analysis of parameter using hydrologic data of 2002. The sensitivity analysis showed that soil moisture index versus runoff percent (SMI-ROP), baseflow infiltration index versus baseflow percent (BII-BFP) and surface-subsurface separation (S-SS) parameters are higher sensitive parameters to the simulation result.

• Journal of The Korean Society of Agricultural Engineers
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• v.56 no.2
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• pp.1-9
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• 2014

A modeling system is constructed by integrating an one-dimensional unsteady flow simulation model and a hydrologic model to simulate flood flows in drainage channel networks of paddy field districts. The modeling system's applicability is validated by simulating flood discharges from a paddy field district, which consists of nine paddy fields and one drainage channel. The simulation results are in good agreement with the observed. Particularly, in the verification stage, the relative errors of peak flows and peak depths between the observed and simulated hydrographs range 8.96 to 10.26 % and -10.26 to 2.97 %, respectively. The modeling system's capability is compared with that of a water balance equation-based model; it is revealed that the modeling system's accuracy is superior to the other model. In addition, the simulations of flood discharges from large-sized paddy fields through drainage channels show that the flood discharge patterns are affected by drainage outlet management for paddy fields and physical characteristics of the drainage channels. Finally, it is concluded that to efficiently design drainage channel networks, it is necessary to analyze the results from simulating flood discharges of the drainage channel networks according to their physical characteristics and connectivities.

• Journal of the Korean Society of Hazard Mitigation
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• v.8 no.6
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• pp.137-148
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• 2008

There have been many cases of using wetlands as an alternative in controlling stormwater, treating mining leachate, and agricultural discharge, and so on, recently. The reality is, however, that the wetlands are not properly applicable because of the lack of enough longterm data for wetlands due to the difficulty of long-term monitoring. Therefore, this study tries to analyze the storage of Upo, Mokpo, Sajipo, and Jjokjibeul in Topyeong watershed using SWAT(Soil and Water Assessment Tool) model, one of the long-term runoff hydrologic model, for the purpose of generating the long-term data and analyzing the hydrologic behavior of wetlands based on the generated data. Also, the changes in runoff at the outlet are analyzed after applying the simulation of constructing washland in Topyeong watershed and the storage in Upo is analyzed. The result shows that the runoff at the outlet of the watershed is decreased in rainy season from July to August and increased in dry season from December to February. In addition, the analysis of Upo storage concludes that Upo can be influenced by the construction of the washland. The duration curve of washland is then analyzed in order to evaluate the wetland's sustainability in terms of washland and it appears that the runoff of washland is simulated to be less than that of the existing wetland. Moreover, runoffs of some washlands are simulated to be less even in wet season. These results lead to the fact that there should be further hydrologic management for constructed washland. Then, the changes in loads (TN and TP) because of constructing washland are analyzed. The result shows that the loads are reduced because of the construction. Also, the changes in loads due to the construction of buffer strips are analyzed to compare the load reductions caused by a washland. Finally, REMM model, a riparian management model, is applied to overcome the hydrologic ambiguousness of SWAT model, and then, the SWAT model results are compared to those of REMM.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.1B
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• pp.1-9
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• 2008

The impact of snow accumulation and snowmelt in rainfall-runoff modelling was analyzed for the Soyanggang dam basin by comparing the measured and simulated discharges simulated by the NWS-PC model. Sugawara's conceptual model was used to simulate the snow accumulation and snowmelt phenomena and NWS-PC model was employed to simulate rainfall-runoff. Parameters in model calibration were estimated by the Multi-step Automated Calibration Scheme and optimized using SCE-UA algorithm in each step. The results of the model calibration and verification show that the model considering snowmelt process is better than the one without consideration of snowmelt under the performance criteria such as RMSE, PBIAS, NSE, and PME. The measured discharge time series has over 60 days of persistence. Correlograms for each simulation showed that the simulated discharge with snowmelt model reproduce the persistence closely to the measured discharge's while the one without snow accumulation and snowmelt model reproduce only 20 days of persistence. The study result indicates that the inclusion of snow accumulation and snowmelt model is important for the accurate simulation of rainfall-runoff phenomena in the Soyanggang dam basin.

• Journal of Wetlands Research
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• v.11 no.1
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• pp.49-64
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• 2009

Rainfall-runoff models are used for efficient management, distribution, planning, and design of water resources in accordance with the process of hydrologic cycle. The models simplify the transition of rainfall to runoff as rainfall through different processes including evaporation, transpiration, interception, and infiltration. As the models simplify complex physical processes, gaps between the models and actual rainfall events exist. For more accurate simulation, appropriate models that suit analysis goals are selected and reliable long-term hydrological data are collected. However, uncertainty is inherent in models. It is therefore necessary to evaluate reliability of simulation results from models. A number of studies have evaluated uncertainty ingrained in rainfall-runoff models. In this paper, Meta-Gaussian method proposed by Montanari and Brath(2004) was used to assess uncertainty of simulation outputs from rainfall-runoff models. The model, which estimates upper and lower bounds of the confidence interval from probabilistic distribution of a model's error, can quantify global uncertainty of hydrological models. In this paper, Meta-Gaussian method was applied to analyze uncertainty of simulated runoff outputs from $Vflo^{TM}$, a physically-based distribution model and HEC-HMS model, a conceptual lumped model.