• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.11
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• pp.26-41
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• 2016

Catchment Hydrologic Cycle Assess Tool (CAT) is a model for hydrologic cycle assessment based on physical parameters. In this study, CAT was applied for short-term runoff simulation and connected with model-independent parameter estimation (PEST) for auto-calibrating parameters. The model performance was compared with HEC-HMS, which is widely used for short-term runoff simulation. The study area is the Pangyo Watershed ($22.9km^2$), which includes the Unjung-Cheon and Geumto-Cheon tributaries of the Tan-Cheon stream. Simulation periods were selected from six rainfall events of a two-year period (2006-2007). For the runoff simulation, CAT was applied using three types of infiltration methods (excess rainfall, Green and Ampt and Horton). Sensitivity analysis was carried out to select the parameters and then CAT was optimized using PEST. The model performance of HEC-HMS and CAT-PEST for the rainfall events were within an acceptable limit with Nash Sutcliffe efficiencies (NSE) of 0.63-0.91 and 0.42-0.93, respectively. The simulation results of HEC-HMS have high accuracy in the case of rainfall events that have a sensitive relationship between initial soil moisture conditions and runoff characteristics. The results of CAT-PEST indicated the possibility of reflecting a real runoff system using various physical parameters.

• Journal of Ecology and Environment
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• v.39 no.1
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• pp.71-80
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• 2016

The main goal of this study is to develop a multi-metric fishway assessment model (M_m-FA) and evaluate the efficiency of fishway. The M_m-FA model has three major fishway components with nine metrics: structural characteristics, hydraulic/hydrologic features, and biological attributes. The model was developed for diagnosing and assessing fishway efficiency and tested to Juksan Weir at the Yeongsan River Watershed. Structural characteristics of fishway included slope of the fishway (M₁), ratios of fishway width to stream width (M₂), and the proportion of orifice clogging and orifice size (M₃). Hydraulic/hydrologic characteristics included depth of fishway entrance head (M₄), depth of exit tail (M₅), and current velocity of inner fishway (M₆). Biological characteristics included fish species ratio of inner fishway to upper-lower weir (M₇), fish length distribution (M₈), and the proportion of migratory fish species to the total number of species (M₉). Overall, the assessment of fishway efficiency showed the total score of the M_m-FA model was 25 in the Juksan Weir, indicating "good condition" by the criteria of the five-level classification system. The M_m-FA model may be used as a key tool for the assessment of fishway efficiency, especially on the 16 weirs constructed for the "Four Rivers Restoration Project" after a partial calibration of M_m-FA model.

• Journal of Korea Water Resources Association
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• v.35 no.6
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• pp.817-826
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• 2002

Many researchers have been tried to forecast the future as analyzing data characteristics and the forecasting methodology may be divided into two cases of deterministic and stochastic techniques. However, the understanding data characteristics may be very important for model construction and forecasting. In the sense of this view, recently, the deterministic method known as nonlinear dynamics has been studied in many fields. This study uses the geometrical methodology suggested by Poincare for analyzing nonlinear dynamic systems and we apply the methodology to understand the characteristics of known systems and hydrologic data, and determines the possibility of forecasting according to the data characteristics. Say, we try to understand the data characteristics as constructing Poincare map by using Poincare section and could conjecture that the data sets are linear or nonlinear and an appropriate model.

• Journal of Wetlands Research
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• v.21 no.spc
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• pp.16-27
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• 2019

Alteration in the flow regime of rivers are caused by natural climate change and the changes in anthropogenic hydrological environment due to dam construction. These changes in flow regime cause serious changes not only in the fresh water ecosystems of the rivers but also in the physical structures and fish habitats of the streams. In this study, the alteration in the hydrological characteristics of the Gam river basin due to Buhang dam construction and the changes in ecological health condition, water quality, and river cross-section were analyzed. As a result of analysis by indicators of hydrologic alteration (IHA) to quantitatively change the flow regime of Gam river, HA (Hydrologic Alteration) is more than ±1 and various changes have occurred in the river ecosystem after Buhang dam construction. In addition, ecological health condition and water quality showed different response for each element, and in the case of riverbeds and channel cross-sections, the degradation of channel bed was obviously monitored after dam construction. The results of this study are expected to be used as an efficient method for evaluating changes in stream ecosystems caused by stream regime changes.

• Journal of Korea Water Resources Association
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• v.37 no.7
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• pp.599-612
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• 2004

The continuous long-term rainfall-runoff simulation model SWAT has the advantage of being able to account for various land use, however, SWAT lacks the capability of simulating the drainage characteristics of urban area. On the other hand, SWMM, which is the most popular model for runoff analysis of urban watershed, has the advantage of being capable of considering surface and drainage characteristics in urban area, but SWMM cannot easily account for land use other than urban area within a watershed. In this study, SWAT-SWMM model, which builds on the strengths of SWAT and SWMM, has been applied to the Osan River Watershed which is a tributary watershed to the Gyung-Ahn River. From the application, the results from coupled SWAT-SWMM model has been compared to the ones from SWAT for each hydrologic component such as evapotranspiration, surface runoff, groundwater flow, and watershed and channel discharge, and the runoff characteristics of two models for each hydrologic component has been discussed.

• Journal of Korea Water Resources Association
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• v.51 no.8
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• pp.739-745
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• 2018

Recently, the incidence of heavy rainfall is increasing. Therefore, a rainfall analysis should be performed considering increasing frequency. The current rainfall analysis for hydrologic design use the hourly rainfall data of ASOS with a density of 36 km on the Korean Peninsula. Therefore, medium and small scale watershed included Thiessen network at the same rainfall point are analyzed with the same design rainfall and time distribution. This causes problem that the watershed characteristics can not be considered. In addition, there is a problem that the temporal-spatial change of the heavy rainfall occurring in the range of 10~20 km can not be considered. In this study, Author estimated design rainfall considering heavy rainfall using minutely rainfall data of AWS, which are relatively dense than ASOS. Also, author analyzed the time distribution and runoff of each case to estimate the huff's method suitable for the watershed. The research result will contribute to the estimation of the design hydrologic data considering the heavy rainfall and watershed characteristics.

• Journal of Korea Water Resources Association
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• v.36 no.6
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• pp.911-924
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• 2003

Many researches have been conducting on extracting geometry data and hydrologic parameters by using GIS technique. However, there is no clear standard on those methods yet. This study examines the changing pattern of runoff responses characteristics with applying lumped model on divided watershed. WMS is used in order to divide watershed and calculate hydrologic geometry data and parameters by GIS technique. HEC-1 is adopted as a hydrologic model to establish runoff responses. The basin is divided into small watersheds, which are approximately same size. This research conducted runoff response simulation of Pyoungchang River and Wichon River Basin. Especially, research was focused on what is the most appropriate level as a divined sub-basin, and tested the effect of size of sub-basin for the runoff response simulation. The results showed the size of sub-basin was not an important factor for the simulation results after a certain size. The results of this study can be applied as an appropriate guidance to select optimal simulation size of watershed for the lumped model in a specific watershed.

• Proceedings of the Korea Water Resources Association Conference
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• 2006.05a
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• pp.1444-1449
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• 2006

Korea is about 70% of all country to mountain, and basin is consisted of various terrain, soil, vegetation, land use etc. because use land as intensive. Also, need basin hydrologic model that can analysis base outflow as well as outflow directly for calculation of discharge to establish irrigation plan. Inconvenient in use method and user interface offer side is causing by way that existing USGS WEASEL runs in PC Arc/Info, and ArcGIS with development of present GIS technology is applied in many fields offering convenience in analysis that use GIS. In this research, wished to develop suitable outflow parameter extraction system, For this, develop pre-processor and post-processor that effectively draw of hydrologic model input data from water resources DB through van example benchimarking, and developed input/output component of GIS base applicable to various hydrologic and water quality model.

• Journal of Korea Water Resources Association
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• v.40 no.8
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• pp.585-600
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• 2007

The hydrologic cycle and BOD pollutant loads of all sub-watersheds were analyzed using HSPF (Hydrological Simulation Program-Fortran). At first, sensitivity analyses to water quantity (peak discharge and total volume) and quality (BOD peak concentrations and total loads) were conducted and some critical Parameters were selected. For more precise simulation, the study watershed was divided into four parts according to the landuse characteristics and used climate data and so calibrated and verified respectively. It was found that as the urban area ratio increases in the downstream direction, baseflow decreases (11.1 % $\rightarrow$ 5.0%) and the ratio of direct runoff volume(42.5 % $\rightarrow$ 56.9 %), BOD concentration (3.3 mg/L $\rightarrow$ 15.0 mg/L) and unit loads (55.4 kg/ha/year $\rightarrow$ 354.5 kg/ha/year) increase.

• Journal of Korea Water Resources Association
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• v.47 no.1
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• pp.49-62
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• 2014

As the Urban area grows and more land is developed both within the city and in surrounding areas, hydrologic functions of the natural water cycle are altered. Urbanization creates impervious areas that negatively impact stormwater runoff characteristics. these changes to the natural hydrologic cycle result in the increased flooding, decreased groundwater recharge, increased urban heat island effects. Finally, the land use and other activities result in accumulation and washoff of pollutants from surface, resulting in water quality degradation. Therefore, in this study, evaluating and quantitative analysis of the percolation effect through infiltration experiment of permeable pavement, which is one of the ways that can reduce the problem of the dry stream. Also the SWMM model is used to study the effect of the hydrologic cycle for permeable pavement block contribution.