• Journal of Korea Water Resources Association
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• v.46 no.12
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• pp.1235-1247
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• 2013

This study is to evaluate the climate change impact on future storage behavior of Chungju dam($2,750{\times}10^6m^3$) and the regulation dam($30{\times}10^6m^3$) using SWAT(Soil Water Assessment Tool) model. Using 9 years data (2002~2010), the SWAT was calibrated and validated for streamflow at three locations with 0.73 average Nash-Sutcliffe model Efficiency (NSE) and for two reservoir water levels with 0.86 NSE respectively. For future evaluation, the HadCM3 of GCMs (General Circulation Models) data by scenarios of SRES (Special Report on Emission Scenarios) A2 and B1 of the IPCC (Intergovernmental Panel on Climate Change) were adopted. The monthly temperature and precipitation data (2007~2099) were spatially corrected using 30 years (1977~2006, baseline period) of ground measured data through bias-correction, and temporally downscaled by Change Factor (CF) statistical method. For two periods; 2040s (2031~2050), 2080s (2071~2099), the future annual temperature were predicted to change $+0.9^{\circ}C$ in 2040s and $+4.0^{\circ}C$ in 2080s, and annual precipitation increased 9.6% in 2040s and 20.7% in 2080s respectively. The future watershed evapotranspiration increased up to 15.3% and the soil moisture decreased maximum 2.8% compared to baseline (2002~2010) condition. Under the future dam release condition of 9 years average (2002~2010) for each dam, the yearly dam inflow increased maximum 21.1% for most period except autumn. By the decrease of dam inflow in future autumn, the future dam storage could not recover to the full water level at the end of the year by the present dam release pattern. For the future flood and drought years, the temporal variation of dam storage became more unstable as it needs careful downward and upward management of dam storage respectively. Thus it is necessary to adjust the dam release pattern for climate change adaptation.

• Journal of Environmental Impact Assessment
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• v.20 no.1
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• pp.25-36
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• 2011

In this study, the accurate water quality analysis in rivers, including the non-point source is performed. First of all, watershed model, SWAT(Soil and Water Assessment Tool) was applied to analyze the impact of the non-point source in study area. And then, water quality analysis integrating the point source and the non-point source is implemented using QUALKO model. For more exact simulation, it should be the calibration and verification of variables and parameters which are needed for simulation. In addition, the importance of considering the non-point source was confirmed in river water quality simulation. BOD, TN, TP were analysed, and the results shows that BOD, TN and TP concentration was increased to 16.8%, 8.2% and 25.8% respectively. The more accurate estimate will be carried if use of reliable measurements and watershed simulation be done in models linking process. The suggested technique will improve the accuracy of the water quality analysis. The methodologies presented in this study will contribute to basin-wide water quantity and quality management.

• Journal of Korean Society on Water Environment
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• v.25 no.1
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• pp.125-135
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• 2009

Reliable long-term flows by SWAT-K model were applied to the relationship between stream flow and pollutant load derived from 8-day measured data of Ministry of Environment (MOE) in order to obtain continuous loadograph and evaluate accuracy in water quality modeling for the Chungju dam watershed. The measured flow were compared with flow duration curve from the model, and it showed that measured values corresponded to the almost full range of stream flow conditions except at Odae A. And there was significant relationship ($R^2=0.60{\sim}0.97$) between measured flow and water quality load at all unit-watersheds. Applying this relationship to simulated flows, continuous loadograph was obtained and compared with modeled pollutant loads. Although there were some differences during some dry and flood seasons, those were not significant and overall trend showed a good agreement. From the results, we would be able to derive a continuous loadograph based on measured data at total maximum daily loads (TMDLs) unit-watersheds on a national scale, in which stream flow and water quality have been measured at 8-day intervals since 2004, and this could be helpful to utilize distributed water quality models with difficulty in calibrating and validating parameters from lack of measured data at present.

• Proceedings of the Korea Water Resources Association Conference
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• 2018.05a
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• pp.294-294
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• 2018

복잡한 수문 수리지질학적 조건을 고려할 수 있는 SWAT-MODFLOW 지표수-지하수 통합모형과 대수층-하천-양수정 시스템을 단순화한 Hunt (1999) 해석해를 죽산천 인근 지역에 각각 적용하여 지하수 양수로 인한 하천수 감소량을 모의하고 그 결과를 비교하였다. 하천으로부터 약 1 km 이내에 위치한 천부 지하수 관정들 중에서 취수계획량이 $100m^3$/일을 초과하는 18개의 관정을 선별하고 지하수 양수량 대비 하천수 감소량(하천수 감소비)을 산정한 결과 대부분의 관정에서 해석해와 모델링 결과의 차이가 0.2 미만으로 매우 작은 것으로 나타났다. 따라서 해석해가 하천-대수층 시스템을 단순화한 조건에 대해 유도되었음에도 불구하고 정밀한 모델링에 준하는 결과를 나타낼 수 있는 것으로 분석되었다. 그러나, 양수기간이 장기화되거나 하천과 관정간의 이격거리가 증가함에 따라 해석해와 모의결과의 차이가 다소 증가하는 경향을 나타내었다. 해석해가 대수층 저류량의 감소와 하천수량의 감소가 장기적으로 균형을 이루는 동적 평형 상태를 구현할 수 없고 하천수위의 급격한 변화에 따른 하천수와 지하수간의 상호 교환량의 불규칙한 패턴 또한 모사할 수 없는 한계가 있지만 양수기간 5년 이내의 하천수 감소량의 평균적인 거동은 수치모의 결과와 유사한 것으로 평가되었다.

• Journal of Korean Society on Water Environment
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• v.36 no.6
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• pp.592-610
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• 2020

In South Korea, the concept of water environment was expanded to include aquatic ecosystems with the Integrated Water Management implementation. Watershed-scale modeling is typically performed for hydrologic component analysis, however, there is a need to expand to include ecosystem variability such that the modeling corresponds to the social and political issues around the water environment. For this to be viable, the modeling must account for several distinct features in South Korean watersheds. The modeling must provide reasonable estimations for peak flow rate and apply to paddy areas as they represent 11% of land use area and greatly influence groundwater levels during irrigation. These facts indicate that the modeling time intervals should be sub-daily and the hydrologic model must have sufficient power to process surface flow, subsurface flow, and baseflow. Thus, the features required for watershed-scale modeling are suggested in this study by way of review of frequently used hydrologic models including: Agricultural Policy/Environmental eXtender(APEX), Catchment hydrologic cycle analysis tool(CAT), Hydrological Simulation Program-FORTRAN(HSPF), Spatio-Temporal River-basin Ecohydrology Analysis Model(STREAM), and Soil and Water Assessment Tool(SWAT).

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.295-295
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• 2021

수자원 관리 및 계획 수립에 있어 강우 유출 분석은 가장 중요하며, 기본적인 분석이다. 기존의 강우 유출 분석은 일반적으로 수문 모형을 이용한다. 강우 유출 분석은 강수와 증발산 과정, 즉 물순환에 있어 복잡한 상호 작용을 고려해야한다. 본 연구에서는 기존의 수문 모형과 데이터간의 관계를 포착할 수 있는 딥러닝 기법을 이용한 강우 유출분석 수행하였다. 우리나라의 유역 중, 비교적 풍부한 수문데이터를 보유하고 있는 IHP (International Hydrological Program)의 청미천 유역을 연구대상지역으로 연구를 수행하였다. 수문 모형으로는 SWAT (Soil and Water Assessment Tool)을 이용하였으며, 딥러닝 기법은 시계열 분석에 있어 주로 사용되는 RNN(Recurrent Neural Network) 중 LSTM (Long Short-Term Memory) 네트워크를 이용하였다. 분석결과 수문 모형의 성능 지표인 상관계수와 NSE (Nash-Sutcliffe Efficiency)는 LSTM 네트워크에서 더 높은 성능을 확인 할 수 있었다. 일반적으로 LSTM 네트워크는 보정 기간이 길수록 더욱 좋은 성능을 나타낸다. 즉, 과거 수문데이터가 충분히 확보된 유역에서 LSTM 네트워크와 같은 데이터 기반 모델은 다양한 지형 및 기상데이터를 필요하는 수문 모델보다 유용할 것이라 사료된다.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.330-330
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• 2021

본 연구에서는 새롭게 개발 중인 SSP 시나리오의 일단위 강수량과 온도 자료를 활용하여 청미천 유역의 미래 가뭄의 예측 및 분석을 실시하였다. SSP1-2.6, SSP2-4.5, SSP3-7.0, SSP5-8.5에 따른 새롭게 개발 중인 CMIP6 (Coupled Model Intercomparison Project) GCM (General Circulation Models) 중 ACCESS-ESM1.5(Australian Community Climate and Earth System Simulator model)를 이용하였다. GCM 자료는 Quantile Mapping 방법을 사용하여 편이보정 되었고, 유출분석은 SWAT(Soil and Water Assessment Tool) 모형을 사용하여 청미천 유역에 대해 수행하였다. 청미천 유역의 가뭄분석을 위해 기상학적 가뭄지수인 SPI(Standardized Precipitation Index)와 SPEI(Standardized Precipitation Evapotranspiration Index), 수문학적 가뭄지수인 SDI(Standardized Streamflow Index)를 산정하였다. 그 후, 시간에 따른 가뭄의 특성을 분석하기 위해 가까운 미래 (2025-2064)와 먼 미래 (2065-2100) 로 구분하여 분석을 진행하였다. 그 결과, 청미천 유역의 가뭄 발생은 SSP시나리오, 가뭄지수에 따라 차이점을 확인할 수 있었다. SSP 시나리오의 경우 SSP5-8.5에서 가장 심각한 가뭄이 발생하였다. 가뭄지수의 경우 강수만을 고려한 SPI는 먼 미래에 비해 가까운 미래에서 더욱 심각한 가뭄이 발생하였다. SDI의 경우 강수량의 변동이 일반적으로 하천의 흐름에 영향을 미치기에 SPI와 비슷한 양상을 나타내었다. SPEI의 경우 시간에 따른 기온상승으로 먼 미래에 심각한 가뭄이 발생하였다.

• Journal of The Korean Society of Agricultural Engineers
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• v.62 no.4
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• pp.99-110
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• 2020

The objective of this study is to analyze the trend of changes in the water circulation rates under climate change by adopting the concept of WCR defined by the Ministry of Environment. With the need for sound water circulation recovery, the MOE proposed the idea of WCR as (1-direct flow/precipitation). The guideline for calculating WCR suggests the SCS method, which is only suitable for short term rainfall events. However, climate change, which affects WCR significantly, is a global phenomenon and happens gradually over a long period. Therefore, long-term trends in WCRs should also be considered when analyzing changes in WCR due to climate change. RCP (Representative Concentration Pathway) 4.5 and 8.5 scenarios were used to simulate future runoff. SWAT (Soil and Water Assessment Tool) was run under the future daily data from GCMs (General Circulation Models) after the calibration. In 2085s, monthly WCR decreased by 4.2-9.9% and 3.3-8.7% in April and October. However, the WCR in the winter increased as the precipitation during the winter decreased compared to the baseline. In the aspect of yearly WCR, the value showed a decrease in most GCMs in the mid-long future. In particular, in the case of the RCP 8.5 scenario, the WCR reduced 2-3 times rapidly than the RCP 4.5 scenario. The WCR of 2055s did not significantly differ from the 2025s, but the value declined by 0.6-2.8% at 2085s.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.17 no.4
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• pp.1-15
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• 2014

Forest ecosystems generate variety of important goods and services for human well-being. As a growing concern of climate change and water shortage, it is necessary to quantify, model and map water balance in forest. In this study, we have analyzed 11 overseas forest water supply models (AIM, ATEAM, CENTURY, (E)SWAT, GUMBO, InVEST, PLM, SAVANNA, WaSSI, WaterGAP, WBM) and compared their scale, input and out data, availability of the models and analyzed the applicability of the models to Korea. As a result, InVEST and WaterGAP model appeared to be applicable for quantifying water provisioning services in Korea. A systematic approach for applying to evaluate water balance in forest was suggested based on our quantification approach.

• Journal of Korea Water Resources Association
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• v.50 no.10
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• pp.703-714
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• 2017

This paper analyzes the impact of two climate change scenarios on flow rate and water quality of the Yongdam Dam and its basin using CE-QUAL-W2 and SWAT, respectively. Under RCP 4.5 and RCP 8.5 scenarios by IPCC, simulations were performed for 2016~2095, and the results were rearranged into three separate periods; 2016~2035, 2036~2065 and 2066~2095. Also, the result of each year was divided as dry season (May~Oct) and wet season (Nov~Apr) to account for rainfall effect. For total simulation period, arithmetic average of flow rate and TSS (Total Suspended Solid) and TP (Total Phosphorus) were greater for RCP 4.5 than those of RCP 8.5, whereas TN (Total Nitrogen) showed contrary results. However, when averaged within three periods and rainfall conditions the tendencies were different from each other. As the scenarios went on, the number of rainfall days has decreased and the rainfall intensities have increased. These resulted in waste load discharge from the basin being decreased during the dry period and it being increased in the wet period. The results of SWAT model were used as boundary conditions of CE-QUAL-W2 model to predict water level and water quality changes in the Yongdam Dam. TSS and TP tend to increase during summer periods when rainfalls are higher, while TN shows the opposite pattern due to its weak absorption to particulate materials. Therefore, the climate change impact must be carefully analyzed when temporal and spatial conditions of study area are considered, and water quantity and water quality management alternatives must be case specific.