• Journal of Korea Water Resources Association
• /
• v.37 no.4
• /
• pp.305-314
• /
• 2004

Climate change mainly due to the increase of green house gases cause different patterns of water cycle within the basin. However, it is common that current planning and management practices do not consider the effect of the climate change. So, this study evaluated the effect of climate change on the water circulation within the watershed. This study used several GCM simulations for the double $CO_2$condition for the generation of temperature and rainfall series using the Markov chain. Daily runoff series for 100 years were generated using a rainfall-runoff model. As results. annual temperature increase by ＋3.2 ∼＋4.6$^{\circ}C$, annual precipitation change －7 ∼ ＋8 %, annual runoff change －14 ∼ ＋7 %, and potential evapotranspiration amount change ＋3 ∼＋4 % for the change of 1 $^{\circ}C$ are found to be expected depending on GCM simulations. Even though the simulation results are very dependent on the GCM predictions considered, overall variability of runoff is expected to become higher than the current state.

• Journal of The Korean Society of Agricultural Engineers
• /
• v.48 no.6
• /
• pp.89-100
• /
• 2006

In order to estimate delivered nutrients load from non-point sources in the Gap stream watershed in Daejeon, a distributed watershed model SWAT2000 was used so that it could predict the impact of land management practices on water, sediments and chemicals yields in large complex watersheds with varing soils, land uses and management condition over long period of time. The SWAT2000 was applied to the Daejeon (Indong), Yudeung (Boksu) and Gap (Hoeduck) streams for TMDL (Total Maximum Daily Load) of nutrients. The observed water quality and streamflow data of the year of 2002 and 2003 were used for calibration, and those of the year 2004 and 2005 were used for validation. Simulated results were evaluated by Estimation Efficiency Analysis (COE), Regression Analysis $(R^2)$ and Relative Error (R.E.) for the nutrients amounts on the monthly and yearly basis by comparing observed load with estimated load obtained by using SWAT2000 simulations. The COE value fur T-N was ranged from 0.59 to 0.78, $R^2$ values for T-N ranged from 0.65 to 0.84, and R.E values fur T-N load ranged from 4% to 20%. COE value far T-N was ranged from 0.59 to 0.73, $R^2$ values for T-P ranged from 0.67 to 0.82, and R.E values for T-P load ranged from 3% to 25%. Estimated results of SWAT2000 simulation for 3 sites (Indong, Boksu, Hoedeok) were reasonably satisfactory. This study indicated that SWAT2000 model could be applicable to estimate the nutrients load from the Gap stream watershed in Korea.

• Journal of Korea Water Resources Association
• /
• v.42 no.10
• /
• pp.877-889
• /
• 2009

This study is to assess the future potential impact of climate change on stream water quality for a 6,581.1 km$^2$ dam watershed using SWAT (Soil and Water Assessment Tool) model. The ECHAM5-OM climate data of IPCC (The Intergovernmental Panel on Climate Change) A2, A1B, and B1 emission scenarios were adopted and the future data (2007-2099) were corrected using 30 years (1977-2006, baseline period) weather data and downscaled by Change Factor (CF) method. After model calibration and validation using 6 years (1998-2003) observed daily streamflow and monthly water quality (SS, T-N, and T-P) data, the future (2020s, 2050s and 2080s) hydrological behavior and stream water quality were projected.

• Journal of Korea Water Resources Association
• /
• v.55 no.5
• /
• pp.321-331
• /
• 2022

In this study, we tried to present a method for calculating the amount of regression using a watershed modeling method that can simulate the hydrological mechanism of water balance analysis and agricultural water based on watershed unit. Using the soil water assessment tool (SWAT), a watershed water balance analysis was conducted considering the simulation of paddy fields for the Manbongcheon Standard Basin (97.34 km²), which is a representative agricultural area of the Yeongsan river basin. Before evaluating return flow, the SWAT was calibrated and validated using the daily streamflow observation data at Naju streamflow gauge station (NJ). The coefficient of determination (R²), Nash-Sutcliffe Efficiency (NSE), Root-Mean-Square Error (RMSE) of NJ were 0.73, 0.70, 0.64 mm/day. Based on the calibration results for three years (2015-2017), the quick return flow and the return rate compared to the water supply amount for the irrigation period (April 1 to September 30) were calculated, and the average return flow rate was 53.4%. The proposed method of this study may be used as foundation data to optimal agricultural water supply plan for rational watershed management.

• Journal of Korea Water Resources Association
• /
• v.48 no.10
• /
• pp.793-806
• /
• 2015

The simulation of natural streamflow at ungauged basins is one of the fundamental challenges in hydrology community. The key to runoff simulation in ungauged basins is generally involved with a reliable parameter estimation in a rainfall-runoff model. However, the parameter estimation of the rainfall-runoff model is a complex issue due to an insufficient hydrologic data. This study aims to regionalize the parameters of a continuous rainfall-runoff model in conjunction with a Bayesian statistical technique to consider uncertainty more precisely associated with the parameters. First, this study employed Bayesian Markov Chain Monte Carlo scheme for the estimation of the Sacramento rainfall-runoff model. The Sacramento model is calibrated against observed daily runoff data, and finally, the posterior density function of the parameters is derived. Second, we applied a multiple linear regression model to the set of the parameters with watershed characteristics, to obtain a functional relationship between pairs of variables. The proposed model was also validated with gauged watersheds in accordance with the efficiency criteria such as the Nash-Sutcliffe efficiency, index of agreement and the coefficient of correlation.

• Korean Journal of Ecology and Environment
• /
• v.40 no.1
• /
• pp.155-162
• /
• 2007

Water balance is the major factor in forest ecosystem, and is closely related to the vegetation and topographic characteristics within a watershed. The hydrologic response of a forest watershed was investigated with the hydrological model. The deterministic, lumped parameter model (BROOK90) was selected and used to evaluate the applicability of the model for simulating daily runoff on the steep, forested watershed. The model was calibrated and validated against the streamflow data measured at the Bukmoongol watershed. The deviation in runoff volume $(D_v)$ was -1.7% for the calibration period, and the $D_v$ value for the validation period was 4.6%. The correlation coefficient (r) and model efficiency (E) on monthly basis were 0.922,0.847, respectively, for the calibration period, while the r- and E-value for the validation period were 0.941, 0.871, respectively. Overall, the simulated streamflows were close to the observations with respect to total runoff volume, seasonal runoff volume, and baseflow index for the simulation period. BROOK90 model was able to reproduce the trend of runoff with higher correlation during the simulation period.

• Journal of Korea Water Resources Association
• /
• v.33 no.5
• /
• pp.623-634
• /
• 2000

This study describes results of numerical simulations on river flow response due to global warming. Forecasts of changes in climatic conditions are required to estimate the hydrologic effects of increasing trace gas concentrations in the atmosphere. However, reliable forecasts of regional climate change are unavailable. In there absence, various approaches to the development of scenarios of future climatic conditions are used. The approach in this study is to prescribe climatic changes for a river basin in a simplified manner. As a rule, such scenarios specify air temperature increases from $0^{\circ}C\;to\;4.0^{\circ}C$ and precipitation change (increase or decrease) in the range of 0% to 15%. On the basis of acceptable supposition of warming scenarios. future daily streamflow is simulated using rainfall-runoff model in the Andong Dam basin. The numerical experiments have quantitatively revealed the change of discharge at 2010, 2020, 2030 and 2050 for each warming scenarios and compared it with the results for a non-warmmg scenano.cenano.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2010.05a
• /
• pp.1154-1158
• /
• 2010

최근 전 세계적으로 GIS (Geographic Information Science) 및 RS (Remote Sensing) 데이터 등 디지털정보의 구축이 급속도로 진행되고 있고, 이들의 발달로 유역에 대한 정확하고 상세한 각종 수문매개변수 수집이 가능하여 유역을 부분유역으로 분할한 기존의 집중형 수문모형보다 유역내의 공간적인 유량변동을 보다 상세하게 고려할 수 있는 격자기반의 분포형 수문모형의 활용도가 높아지고 있다. 유역의 수문특성 및 지형특성을 동일한 매개변수로 적용하기 때문에 유역의 공간적인 수문 및 지형특성을 표현하기 어려운 집중형 모형과 달리 강우-유출해석에 있어서 분포형 모형은 실제 복잡한 유역에서의 유출과정 또는 물질의 수문순환과정을 잘 이해할 수 있고, 어떤 유역의 토지이용형태의 변화가 초래하는 영향과 효과를 사전에 예측할 수 있으며, 신뢰성 있는 과거의 수문자료가 없거나 부족한 유역에서의 유출 계산이 용이하다. 따라서 본 연구에서는 Fortran 90을 개발언어로 사용하여 GIS Data와 위성영상을 활용해 유출량을 모의하는 분포형 물수지 유출 모형을 개발하여 금강 상류유역인 용담댐 유역($930km^2$)을 대항으로 2000~2008년의 일 유출량을 모의하였다. 모형은 크게 3개의 모듈(유출량, 증발산량, 토양수분) 형태로 구성되었으며, 유출량은 강우 전 토양의 저류능을 추적하여 산정하였다. 모형의 결과는 셀별 값을 가지는 분포형으로 출력되며, 유역의 평균 수문자료가 Text file로 출력된다. 민감도 분석을 통하여 최적의 유출 관련 매개 변수를 선정하고 하류의 댐 유입량 자료를 바탕으로 모형의 보정(2001-2004) 및 검증(2005-2008)을 실시하였다. 유출량에 대한 Nash-Sutcliffe 모형효율은 0.78~0.93로 모의치가 실측치의 경향을 잘 표현하는 것으로 나타났다. 유출량 분포도는 강우량을 매우 잘 반영하였으며, 같은 강우조건하에서 토양의 배수조건에 따라 유출이 확연히 다르게 표현되었다.

• Journal of the Korean Association of Geographic Information Studies
• /
• v.21 no.3
• /
• pp.104-118
• /
• 2018

This study is to evaluate the accuracy improvement of the model using SWAT(Soil and Water Assessment Tool) model and multi - point hydrological observation data. The watershed is located in the Yongdam Dam($930.4km^2$), the Donghyang($165.5km^2$), the Chuncheon($290.9km^2$), the Juchun($57.8km^2$) and the Seokjeong($80.5km^2$). The watershed covers 70.0 % forest. In order to improve the accuracy of the model, precipitation data were used from two weather stations(Jangsu, Geumsan) and 16 AWS stations daily precipitation data(2003~2011) managed by KMA, MLIT, and K-water. Based on the reliable data of the Yongam test basin in 2003~2011, the runoff of single point (Yongdam dam) and multi-point (Donghyang, Chuncheon, Jucheon, Seokjeong). Simulation results show that the $R^2$ of the single subwatershed (Donghyang, Chuncheon, Jucheon, Seokjeong) is single point(0.84) and multipoint(0.88). For model efficiency coefficient of Nash-Sutcliffe at single point(0.45) and multipoint(0.70).

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.28 no.5B
• /
• pp.495-504
• /
• 2008

Evapotranspiration (ET) is an important state variable while simulating daily streamflow in hydrological models. In the estimation of ET, for example, when using FAO Penman Monteith equation, the LAI (Leaf Area Index) value reflecting the conditions of vegetation generally affects considerably. Recently in evaluating the vegetation condition as a fixed quantity, the remotely sensed LAI from MODIS satellite data is available, and the time series values of spatial LAI coupled with land use classes are utilized for ET evaluation. Four years (2001-2004) of MODIS LAI was prepared for the evaluation of Penman Monteith ET in the continuous hydrological model, SLURP (Semi-distributed Land Use-based Runoff Processes). The model was applied for simulating the dam inflow of Chungju watershed ($6661.3km^2$) located in the upstream of Han river basin. For four years (2001-2004) dam inflow data and meteorological data, the model was calibrated and verified using MODIS LAI data. The average Nash-Sutcliffe model efficiency was 0.66. The 4 years watershed average Penman Monteith ETs of deciduous, coniferous, and mixed forest were 639.1, 422.4, and 631.6 mm for average MODIS LAI values of 3.64, 3.50, and 3.63 respectively.