• Korean Journal of Ecology and Environment
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• v.44 no.3
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• pp.292-302
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• 2011

The Lake Sihwa watershed includes industrial, urban, and rural areas simultaneously. In this study, we analyzed the characteristics of dissolved organic matter (DOM) in spatial-temporal runoff patterns at representative sites having different land use in the watershed of Lake Sihwa. The result of synchronous and 3D-EEMs(3-Dimensional Excitation Emission Matrix Spectroscopy) analysis in 4TG (industrial area), fluorescence distribution and variation clearly appeared in the Fulvic-like fluorescence (FLF) and Humic-like fluorescence (HLF) regions along with the Protein-like fluorescence (PLF) region. A characteristic that Peak A (HLF) region fluorescence intensity did not decrease and the HLF region of fluorescence intensity and spatial-temporal changes clearly appeared during rainfall in AS (urban area). The results of fluorescence analysis in MS did not show great changes in PLF and FLF while showing that fluorescence intensity changes over time in the Terrestrial-like fluorescence (THLF) region increased greatly. In conclusion, our results showed significant differences in the runoff characteristics of DOM particularly in industrial, urban and rural area, and these differences should be considered for the efficient controlling of DOM in the watershed.

• Journal of Korea Water Resources Association
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• v.51 no.2
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• pp.151-163
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• 2018

The objective of this study was to estimate LOADEST (LOAD Estimator) coefficients for simulating pollutant loads in ungauged watersheds. Regression models of LOADEST were used to simulate pollutant loads, and the multiple linear regression (MLR) was used for coefficients estimation on watershed characteristics. The fifth and third model of LOADEST were selected to simulate T-N (Total-Nitrogen) and T-P (Total-Phosphorous) loads, respectively. The results and statistics indicated that regression models based on LOADEST simulated pollutant loads reasonably and model coefficients were reliable. However, the results also indicated that LOADEST underestimated pollutant loads and had a bias. For this reason, simulated loads were corrected the bias by a quantile mapping method in this study. Corrected loads indicated that the bias correction was effective. Using multiple regression analysis, a coefficient estimation methods according to the watershed characteristic were developed. Coefficients which calculated by MLR were used in models. The simulated result and statistics indicated that MLR estimated the model coefficients reasonably. Regression models developed in this study would help simulate pollutant loads for ungauged watersheds and be a screen model for policy decision.

• Journal of Korean Society of Disaster and Security
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• v.14 no.2
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• pp.1-11
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• 2021

Recently, in Korea, the risk of meteorological disasters is increasing due to climate change, and the damage caused by rainfall is being emphasized continuously. Although the current weather forecast provides quantitative rainfall, there are several difficulties in predicting the extent of damage. Therefore, in order to understand the impact of damage, the threshold rainfall for each watershed is required. The damage caused by rainfall occurs differently by region, and there are limitations in the analysis considering the characteristic factors of each watershed. In addition, whenever rainfall comes, the analysis of rainfall-runoff through the hydrological model consumes a lot of time and is often analyzed using only simple rainfall data. This study used GIS data and calculated the threshold rainfall from the threshold runoff causing flooding by coupling two hydrologic models. The calculation result was verified by comparing it with the actual case, and it was analyzed that damage occurred in the dangerous area in general. In the future, through this study, it will be possible to prepare for flood risk areas in advance, and it is expected that the accuracy will increase if machine learning analysis methods are added.

• Journal of Korea Water Resources Association
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• v.54 no.spc1
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• pp.1183-1193
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• 2021

Low flow affects various fields such as river water supply management and planning, and irrigation water. A sufficient period of flow data is required to calculate the Flow Duration Curve. However, in order to calculate the Flow Duration Curve, it is essential to secure flow data for more than 30 years. However, in the case of rivers below the national river unit, there is no long-term flow data or there are observed data missing for a certain period in the middle, so there is a limit to calculating the Flow Duration Curve for each river. In the past, statistical-based methods such as Multiple Regression Analysis and ARIMA models were used to predict sulfur in the unmeasured watershed, but recently, the demand for machine learning and deep learning models is increasing. Therefore, in this study, we present the DNN technique, which is a machine learning technique that fits the latest paradigm. The DNN technique is a method that compensates for the shortcomings of the ANN technique, such as difficult to find optimal parameter values in the learning process and slow learning time. Therefore, in this study, the Flow Duration Curve applicable to the unmeasured watershed is calculated using the DNN model. First, the factors affecting the Flow Duration Curve were collected and statistically significant variables were selected through multicollinearity analysis between the factors, and input data were built into the machine learning model. The effectiveness of machine learning techniques was reviewed through statistical verification.

• Journal of Korea Water Resources Association
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• v.55 no.5
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• pp.371-381
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• 2022

Since tributaries have greater water quality variability than main streams, a comprehensive evaluation method that considers the effects of various parameters rather than one water quality parameter has been introduced for effective water quality management of tributaries, but the characteristic of the watershed is not considered. In this study, the urbanization rate, livestock excreta generation, and industrial wastewater discharge in the Hantan River middle-watershed classify urban and non-urban watersheds, and evaluate the suitability of water quality indexes by watershed characteristics by analyzing water quality characteristics and calculating CCME WQI, RTWQI, and NSFWQI. Factor analysis was used to understand the effect of water quality parameters used to calculate the water quality index on the water quality index results. As a result of the factor analysis, the relationship between CCME WQI, TC, and FC was derived, and the relationship between RTWQI and DO, SS in urban watersheds and NSFWQI and FC in non-urban watersheds was revealed. As a result of evaluating suitability through comparison with BOD and T-P grades, it was interpreted that the suitability of the water quality index was low in urban watersheds and that comprehensive water quality evaluation using RTWQI was possible in non-urban watersheds.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.35 no.3
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• pp.567-577
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• 2015

Climate and land use changes have impact on availability water resource by hydrologic cycle change. The purpose of this study is to evaluate the hydrologic behavior by the future potential climate and land use changes in Anseongcheon watershed ($371.1km^2$) using SWAT model. For climate change scenario, the HadGEM-RA (the Hadley Centre Global Environment Model version 3-Regional Atmosphere model) RCP (Representative Concentration Pathway) 4.5 and 8.5 emission scenarios from Korea Meteorological Administration (KMA) were used. The mean temperature increased up to $4.2^{\circ}C$ and the precipitation showed maximum 21.2% increase for 2080s RCP 8.5 scenario comparing with the baseline (1990-2010). For the land use change scenario, the Conservation of Land Use its Effects at Small regional extent (CLUE-s) model was applied for 3 scenarios (logarithmic, linear, exponential) according to urban growth. The 2100 urban area of the watershed was predicted by 9.4%, 20.7%, and 35% respectively for each scenario. As the climate change impact, the evapotranspiration (ET) and streamflow (ST) showed maximum change of 20.6% in 2080s RCP 8.5 and 25.7% in 2080s RCP 4.5 respectively. As the land use change impact, the ET and ST showed maximum change of 3.7% in 2080s logarithmic and 2.9% in 2080s linear urban growth respectively. By the both climate and land use change impacts, the ET and ST changed 19.2% in 2040s RCP 8.5 and exponential scenarios and 36.1% in 2080s RCP 4.5 and linear scenarios respectively. The results of the research are expected to understand the changing water resources of watershed quantitatively by hydrological environment condition change in the future.

• Journal of Korea Water Resources Association
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• v.39 no.7 s.168
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• pp.553-562
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• 2006

The relative contributions of overland-flow and stream-flow to the response process at the basin scale are evaluated in the present study. The moments of GIUH models were applied to the data of the Bocheong watershed in the Geum river basin in Korea in order to discuss the feasibility. The GIUH model derived in this study consists of the stream path and overland region. The characteristic velocities for the flows between two cases mentioned above make a clear distinction as expected and would have more physical meaning than the ones of the model by Rodriguez-Iturbe and Valdes(1979). The path lengths of overland for each stream order are nearly constant, whereas the case of stream is shown to grow larger according to the basin sizes. As a result, the overall basin response process was founded out to be greatly under the influence of the hydrodynamic behavior of overland, and its behavior is suggested to be further researched for catching the broader meanings.

• Journal of Korea Water Resources Association
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• v.45 no.1
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• pp.53-64
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• 2012

In this study (II), the module developed in the previous study (I) has been tested on application and numerical stability. The runoff module was compared the result of analysis with two different models (FFC2Q and $Vflo^{TM}$) considering characteristic of infiltration. To examine the application and stability of developed module, runoff aspect was simulated under the variety case of rainfall intensity, effective soil depth, elapsed time. The development module was presented typical type of infiltration process looking physically, the different of saturation point on soil type, and characteristic of soil type. Also, the module was reflected in the runoff feature about rainfall intensity and time distribution. Finally, this paper drew a conclusion that result of rainfall-runoff analysis as compared with difference models (FFC2Q and $Vflo^{TM}$) has a high accuracy.

• Journal of Korean Society of Disaster and Security
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• v.11 no.2
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• pp.83-89
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• 2018

The significant sedimentation at the estuary in the eastern coast of Korea frequently causes river mouth occlusion where disconnection between the river and sea is observed. River mouth occlusion causing watershed retention raises the environmental risk of the area as it impairs water quality and threatens the area's safety in the event of floods. This study proposes a plan to maintain stability of river channel and flow of flood discharge at the estuary with loss of its function for disaster prevention. To this end, the study tries to change the location and width of stream path, focusing on the center line of stream near the sand bar of river mouth. This allows to identify a shape of stream path that leads the most stable flow. To review the result, this study uses the SRH-2D, a model for two-dimensional hydraulic analysis, and conduct numeric simulation. The simulation result showed that the most effective plan for maintaining the stable flow of running water without having the area sensitive to changes in hydraulic characteristics is to lower the overall river bed height of the sand bar near the center line of stream to a equal level.

• Journal of The Korean Society of Agricultural Engineers
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• v.59 no.4
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• pp.85-96
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• 2017

In this research, I performed rainfall monitoring by selecting the spot which can represent high altitude cool farm region in recent 3 years, and tried to understand the characteristic of outflow of non-point pollutants coming from high altitude cool farm region. As a result, it was shown that reducing rainfall runoff in highland farm area can reduce non-point pollution load and should consider priority to reduce runoff through management resources when selecting abatement method. Additionally, it is judged that reduction method related to base run-off should be selected by performing research on material motion of TN.