• Water for future
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• 제25권3호
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• pp.97-104
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• 1992

The distributed hydrologic models are widely applied to estimate the storm-runoff with spatial variability in watershed characteristics and rainfall pattern. This study was aimed to introduce the event-oriented storm runoff model using finite element method, and to try it's applicability on small watershed. Yeonwha watershed was selected and 14 storm events in 1991 were used for the finite element model, and the simulation results were compared with hydrologic quantities.

• Journal of The Korean Society of Agricultural Engineers
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• 제51권6호
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• pp.17-23
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• 2009

The Soil and Water Assessment Tool (SWAT) model was used in this study to evaluate the hydrologic impacts by the impervious surface change in the farm region. The model was calibrated and validated by using four years (1999-2002) of measured data for the Gyeongancheon watershed in Korea. The simulation results agreed well with observed values during the calibration and validation periods. Land use scenarios including various changes of the plastic film house area in the farm region were applied to assess their effects on watershed hydrology. The results indicated that the surface direct (5.6%~14.0%) and total runoff (0.8%~1.5%) increased, but the groundwater discharge (10.7%~27.7%) and evapotranspiration (1.5%~3.3%) decreased as the plastic film house area (5.7%~12.4%) increased.

• Journal of Korea Water Resources Association
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• 제45권5호
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• pp.505-516
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• 2012

The study applies a hydrologic simulation model, HEC-1 developed by Hydrologic Engineering Center to Daecheong dam watershed for modeling hourly inflows of Daecheong dam. Although the HEC-1 model provides an automatic optimization technique for some of the parameters, the built-in optimization model is not sufficient in estimating reliable parameters. In particular, the optimization model often fails to estimate the parameters when a large number of parameters exist. In this regard, a main objective of this study is to develop Bayesian Markov Chain Monte Carlo simulation based HEC-1 model (BHEC-1). The Clark IUH method for transformation of precipitation excess to runoff and the soil conservation service runoff curve method for abstractions were used in Bayesian Monte Carlo simulation. Simulations of runoff at the Daecheong station in the HEC-1 model under Bayesian optimization scheme allow the posterior probability distributions of the hydrograph thus providing uncertainties in rainfall-runoff process. The proposed model showed a powerful performance in terms of estimating model parameters and deriving full uncertainties so that the model can be applied to various hydrologic problems such as frequency curve derivation, dam risk analysis and climate change study.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 한국농공학회 1999년도 Proceedings of the 1999 Annual Conference The Korean Society of Agricutural Engineers
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• pp.51-56
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• 1999

An object-orient watershed runoff model was formulated using the SCS curve number method and routing routines. The four objects included in the model were rainfall , hydrologic unit, reservoir, and channel. Each object considers the data and simulation method to depict the runoff processes. the details of which were presented and discusses in the paper. The resulting model was applied to the HS #3 watershed of the Balan Watershed Project, which is 412.5 ha in size and relatively steep in landscape. The simulated runoff hydrographs from the model were close to the observed data.

• Journal of Korea Water Resources Association
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• 제34권5호
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• pp.511-519
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• 2001

Global warming has begun since the industrial revolution and it is getting worse recently. Even though the increase of greenhouse gases such as $CO_2$is thought to be the main cause for glogal warming, its impact on global climate has not been revealed clearly in rather quantitative manners. The objective of this research is to predict the hydrological environment changes in the Daechung Dam basin due to the global warming. A mesoscale atmospheric/hydrologic model (IRSHAM96 model) is used to predict the possible changes in precipitation and temperature in the Daechun Dam basin. The simulation results of IRSHAM96 model and a conceptual water balance model are used to analyze the changes in soil moisture, evapotranspiration and runoff in the Daechung Dam basin. From the simulation results using the water balance model for 1x$CO_2$and 2x$CO_2$situations, it has been found that the runoff would be decreased in dry season, but increased in wet season due to the global warming. Therefore, it is predicted that the frequency of drought and flood occurrences in the Daechung Dam basin would be increased in 2x$CO_2$condition.

• Journal of Korea Water Resources Association
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• 제41권3호
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• pp.251-264
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• 2008

In this study, a nonhomogeneous markov model which is able to simulate hourly rainfall series is developed for estimating reliable hydrologic variables. The proposed approach is applied to simulate hourly rainfall series in Korea. The simulated rainfall is used to estimate the design rainfall and flood in the watershed, and compared to observations in terms of reproducing underlying distributions of the data to assure model's validation. The model shows that the simulated rainfall series reproduce a similar statistical attribute with observations, and expecially maximum value is gradually increased as number of simulation increase. Therefore, with the proposed approach, the non-homogeneous markov model can be used to estimate variables for the purpose of design of hydraulic structures and analyze uncertainties associated with rainfall input in the hydrologic models.

• Journal of The Korean Society of Agricultural Engineers
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• 제55권6호
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• pp.101-112
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• 2013

Shuttle Radar Topography Mission Digital Elevation Model (SRTM DEM) offers opportunities to make advances in many research areas including hydrology by providing near-global scale elevation measurements at a uniform resolution. Its wide coverage and complimentary online access especially benefits researchers requiring topographic information of hard-to-access areas. However, SRTM DEM also contains inherent errors, which are subject to propagation with its manipulation into analysis outputs. Sensitivity of hydrologic analysis to the errors has not been fully understood yet. This study investigated their impact on estimation of hydrologic derivatives such as slope, stream network, and watershed boundary using Monte Carlo simulation and spatial moving average techniques. Different amount of the errors and their spatial auto-correlation structure were considered in the study. Two sub-watersheds of Geum and Deadong River areas located in South and North Korea, respectively, were selected as the study areas. The results demonstrated that the spatial presentations of stream networks and watershed boundaries and their length and area estimations could be greatly affected by the SRTM DEM errors, in particular relatively flat areas. In the Deadong River area, artifacts of the SRTM DEM created sinks even after the filling process and then closed drainage basin and short stream lines, which are not the case in the reality. These findings provided an evidence that SRTM DEM alone may not enough to accurately figure out the hydrologic feature of a watershed, suggesting need of local knowledge and complementary data.

• Current Research on Agriculture and Life Sciences
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• 제30권2호
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• pp.97-104
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• 2012

Over the last century, drainage systems have become an integral component of agriculture. Climate observations and experiments using General circulation models suggest an intensification of the hydrologic cycle due to climate change. This study presents hydrologic simulations assessing the potential impact of climate change on subsurface drainage in Daegu, Republic of Korea. Historical and Long Ashton Research Station weather generator perturbed future climate data from 15 general circulation models for a field in Daegu were ran into a water management simulation model, DRAINMOD. The trends and variability in rainfall and Soil Excess Water ($SEW_{30}$) were assessed from 1960 to 2100. Rainfall amount and intensity were predicted to increase in the future. The predicted annual subsurface drainage flow varied from -35 to 40 % of the baseline value while the $SEW_{30}$ varied from -50 to 100%. The expected increases in subsurface drainage outflow require that more attention be given to soil and water conservation practices.

• Proceedings of the Korea Society for Simulation Conference
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• 한국시뮬레이션학회 2001년도 The Seoul International Simulation Conference
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• pp.329-334
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• 2001

Many of past studies using physically based numerical climate models indicate that increases in atmospheric $CO_2$could enhance summer dryness over continental region in middle-high latitudes. However the models used in those studies do not take account of permafrost in high latitudes. We have carried out a set of experiments applying a version of global climate model that can reproduce realistic distribution of the permafrost. From the results, it is indicated that permafrost functions as a large reservoir in hydrologic cycle maintaining dry, hot summer over continents in northern middle-high latitudes, and that the $CO_2$warming would reduce this function by causing climatological thawing of permafrost, which would result in moister and cooler summer, and warmer winter in the same region. The present study indicates that an inclusion of very simple description of soil freezing process can make a large difference in a model simulation.

• Journal of Korea Water Resources Association
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• 제53권5호
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• pp.357-367
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• 2020

It is usually not easy to simulate the hydrologic cycle or water quality for ungaged watersheds, especially for long-term simulation. In this paper we evaluated the applicability of GSSHA, a process-based distributed hydrologic model, for the long-term discharge and water quality simulation for the ungaged Peace dam watershed. From the comparative analysis of the simulated discharge and water quality series with measured ones, we concluded that with its overall fair performance on simulating hydrograph patterns of the peak discharges and base flows for major storms the GSSHA model showed some possibility to be used as a watershed model even with its overestimation of peak discharges for small storms and different trends of simulated water quality from measured ones for some periods.