• KSCE Journal of Civil and Environmental Engineering Research
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• v.44 no.4
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• pp.495-501
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• 2024

SWAT-K (Soil and Water Assessment Tool-Korea) model is a long-term runoff model using a soil-centered water balance equation. Soil is crucial for simulating hydrological components, requiring a database (usersoil.dbf) with soil series attribute information. Since the soil property information estimated by soil transfer functions developed overseas does not reflect the characteristics of domestic soil, the Korea Institute of Civil Engineering and Building Technology has established the soil database, which incorporates the results of domestic soil surveys and research from the National Institute of Agricultural Sciences. This study provides a more detailed description of the hydrological component simulation process using soil property information and revises and supplements the previously established soil database to operate in the latest SWAT model. Additionally, by providing this database through the integrated water management platform, it is expected to be utilized not only in the SWAT-K model but also in various watershed hydrological models developed considering soil characteristics.

• Proceedings of the Korea Water Resources Association Conference
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• 2008.05a
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• pp.495-499
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• 2008

This study developed a determination method for a rainwater retention-pumping combination system for roof runoff control. The outflow and stored water volume in the rainwater system was simulated using a water balance equation. Its result is presented in the TPP (Tank capcity-Peak outflow-Pumping rate) curves for rainfall return periods. In a case study on reduction of the peak flow rate of 100-year return period to 5-year in Seoul, The range of pumping rate for $100m^2$ roof area is determined as $0{\sim}25{\ell}$/min. Additionally, retention volume of $8.5{\sim}10m^3$ can be combined with the pumping rate range. That is to say an effective combination of a retention-pumping system capacity can be determined from a system of $8.5m^3$ tank with $25{\ell}$/min to $10m^3$ tank without pump. Using the TPP curves, engineers can determine the effective combination range of retention & pumping system capacity. Furthermore, that can be helpful to decide a detail system capacity for field condition.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.3
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• pp.635-644
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• 1994

A mathematical model was developed to predict the concentrations of various nutrients in supernatants during aerobic digestion which is suitable to be employed in small wastewater treatment plants with such advantages as low capital cost and stable process. Significant reactions were determined with observing the behavior of nitrgen and phosphorus, and the model equations were built up in the form of simultaneous differential equations considering Mass Balance. Laboratory batch experiments were carried out at $20^{\circ}C$ and pH $7.5{\pm}0.5$ on the aerobic digestion of waste activated sludge at different solid levels. Nonlinear regression analysis was performed to estimate various reaction rate constants. The developed model can predict the behavior of Biomass N, dissolved organic N, $NH_4{^-}$-N, $NO_x{^-}$-N, and Biomass P, dissolved organic P, $PO_4{^-}$-P in aerobic digestion process. In this study, the results of simulation showed that dissolved nutrients had more effects on supernatants than nutrients in biomass, and phosphorus was more effective on supernatants than nitrogen.

• Nuclear Engineering and Technology
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• v.23 no.4
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• pp.387-400
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• 1991

An ocean compartment model simulating transport of nuclides by advection due to ocean circulation and intertaction with suspended sediments is developed, by which concentration breakthrough curves of nuclides can be calculated as a function of time. Dividing ocean into arbitrary number of characteristic compartments and performing a balance of mass of nuclides in each ocean compartment, the governing equation for the concentration in the ocean is obtained and a solution by the numerical integration is obtained. The integration method is specially useful for general stiff systems. For transfer coefficients describing advective transport between adjacent compartments by ocean circulation, the ocean turnover time is calculated by a two-dimensional numerical ocean model. To exemplify the compartment model, a reference case calculation for breakthrough curves of three nuclides in low-level radioactive wastes, Tc-99, Cs-137, and Pu-238 released from hypothetical repository under the seabed is carried out with five ocean compartments. Sensitivity analysis studies for some parameters to the concentration breakthrough curves are also made, which indicates that parameters such as ocean turnover time and ocean water volume of compartments have an important effect on the breakthrough curves.

• Journal of Wetlands Research
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• v.15 no.4
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• pp.509-518
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• 2013

Understanding of the exchange between the water and energy which is happening between the surface and atmosphere is the basic of studying water resources. To study these, lots of researches using Noah Land Surface Model(LSM) are in progress. Noah LSM is based on energy and water balance equation and simulates various hydrological factors. There are diverse researches with Noah LSM are ongoing in overseas, on the other hand not enough study has been done. Especially there is almost no study using uncoupled Noah LSM in Korea. In this study we used data from Korea Flux Tower in Haenam(HFK) and Gwangneung(GDK) as forcing data to simulate the model and compared its result of net radiation, sensible heat flux and latent heat flux with the observation data to assess the applicability of Noah LSM in Korea. Regression coefficients of the comparison results of Noah LSM and observation show good agreement with the value of 0.83~0.99 at Haenam and 0.64~0.99 at Gwangneung which means Noah LSM can be trusted.

• Proceedings of the Korea Water Resources Association Conference
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• 1990.07a
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• pp.49-52
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• 1990

강우강도가 큰 집중호우가 지표면에 도달하게 되면 강우량중 상당 부분이 수문학적 손실성분인 침수, 증발산, 차단 및 저류등으로 시간에 따라 분포된다. 이 가운데 지표면에 분포된 식생계 및 낙엽등에 의한 차단(canopy interception effect)과, 지표가 포화시의 증발산(wetted environmental evapotranspiration) 및 각종 저류, 즉 지표면 저류(depression storage), 지표토양층에의 저류(retention storage) 성분 등을 들 수 있으며 이들 각 손실성분은 직접유출로 나타나는 초과우량의 발생시간을 지체시켜 주는 역할을 하나 차단성분 및 저류성분은 시간이 경과함에 따라 결국은 증발산 또는 침투성분으로 흡수된다. 따라서 침투성분은 초과우량 추정에 매우 큰 영향을 줄 뿐 아니라 지표면 아래의 흙의 변형을 야기시키며, 중간유출 및 지하수유출에 기여 한다. 대부분의 호우사상은 강우초기에 강우강도가 지표 흙의 침수계수(hydraulic conductivity)보다 작기 때문에 모두 각 손실성분에 의해 손실되며, 강우강도가 점차 커져 침수능을 초과하면 지표면에 순간적으로 물이 고이게 되는데 이것을 지표심수(surface ponding)라하고, 강우시작부터 이 때까지가 침수시간(ponding time)이 된다. 이 지표침수가 나타나는 순간이 곧 직접유출 시작 시간으로 볼 수 있을 뿐 아니라, 침수시간은 지표면의 물수지면에서 볼 때 초기손실량 및 침수율 결정에 중요한 인자가 된다. 본 연구에서는 각 손실 성분별로 유역의 제반 특성을 고려하여 구한 매개변수로부터 시간에 대한 손실율을 결정하여 산지 하천유역에 발생하는 부정강우사상(unsteady rainfall)의 초과우량을 추정하는 모델을 유도하였다. 대상유역으로는 현재 건설부에서 수행하고 있는 국제수문개발계획(IHP) 대표시험유역 가운데 평창강 수계내의 장평유역으로서, 본 유역은 자기 우량계 및 자기 수위계가 운용되고 있고, 인접 대관령 측후소로부터 기상자료를 획득, 이용할 수 있는 비교적 분석에 양호한 조건을 지닌 유역이다. 모델의 유도 과정은 대상유역 식생계로 피복된 산지유역임으로, 식생차단 저류효과를 고려해서 지표면의 흙에 도달되는 순강우주상도를 얻고 이로부터 침수시간 및 침투율을 결정해서 초과우량을 산정하는 모델을 유도하였다. 강우 지속시간내 즉, 유역이 완전 포화시의 증발산율의 결정은 Morton 모델로부터, 침수시간 및 침투율 결정은 Green-Ampt 방정식을 부정강우사상에 적용할 수 있도록 수정된 모델을 사용하였으며, 분석에 이용된 호우는 1986 ~ 1987년도 발생된 호우사상 가운데 강우강도 및 총 강우량이 비교적 큰 7개 강우사상을 선정하였다. 각 호우사상별로 손실율울 지표면에서 물수지개념을 이용하여 계산하고 산술지상에 구성시킨 결과는 다음 그림과 같다. 이 그림에서 굵은 실선으로 나타낸 곡선(B. L. R)은 각 손실을 곡선을 시간축에 따라 산술평균한 대표손실율곡선이다. 이 대표손실율곡선은 역지수함수형으로서 곡선식의 유도는 회기분석을 이용하였다. 초과우량 주상도를 얻기 위하여 이 대표손실을 곡선을 관측 강우주상도에 적용시켜 본 결과 식생계에 의한 차단 저류율은 약 6mm/hr 정도인 것으로 나타났으며, 이로 인한 침수시간 지체효과는 1~3시간 정도로서 비교적 그 영향이 큼을 알았다. 또한 각 호우사상별 침수시간 계산 결과 그 변동이 큰 것으로 나타났는데 이는 초기 강우강도에 민감하기 때문인 것으로 판단되낟. 한편 유역 포화시의 증발산율은 우기의 기상자료를 이용하여 구한 결과 0.05 - 0.10 mm/hr 의 범위로서 이로 인한 강우손실량은 큰 의미가 없음을 알았다.

• Korean Journal of Agricultural Science
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• v.7 no.2
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• pp.131-144
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• 1980

The Linear Regression Model to extend the monthly runoff data in the short-recorded river was proposed by the author in 1979. Here in this study generalization precedure is made to apply that model to any given river basin and to any given station. Lengthier monthly runoff data generated by this generalized model would be useful for water resources assessment and waterworks planning. The results are as follows. 1. This Linear Regression Model which is a transformed water-balance equation attempts to represent the physical properties of the parameters and the time and space varient system in catchment response lumpedly, qualitatively and deductively through the regression coefficients as component grey box, whereas deterministic model deals the foregoings distributedly, quantitatively and inductively through all the integrated processes in the catchment response. This Linear Regression Model would be termed "Statistically deterministic model". 2. Linear regression equations are obtained at four hydrostation in Geum-river basin. Significance test of equations is carried out according to the statistical criterion and shows "Highly" It is recognized th at the regression coefficients of each parameter vary regularly with catchment area increase. Those are: The larger the catchment area, the bigger the loss of precipitation due to interception and detention storage in crease. The larger the catchment area, the bigger the release of baseflow due to catchment slope decrease and storage capacity increase. The larger the catchment area, the bigger the loss of evapotranspiration due to more naked coverage and soil properties. These facts coincide well with hydrological commonsenses. 3. Generalized diagram of regression coefficients is made to follow those commonsenses. By this diagram, Linear Regression Model would be set up for a given river basin and for a given station (Fig.10).

• The Journal of Engineering Geology
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• v.33 no.1
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• pp.105-119
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• 2023

Water supply is decreasing due to climate change, and coastal and island regions are highly dependent on groundwater, reducing the amount of available water. For sustainable water supply in coastal and island regions, it is necessary to accurately diagnose the current condition and efficiently distribute and manage water. For a precise analysis of the groundwater flow in the coastal island region, submarine fresh groundwater discharge was calculated for the Seongsan basin in the eastern part of Jeju Island. Two methods were used to estimate the thickness of the fresh groundwater. One method employed vertical interpolation of measured electrical conductivity in a multi depth monitoring well; the other used theoretical Ghyben-Herzberg ratio. The value using the Ghyben-Herzberg ratio makes it impossible to accurately estimate the changing salt-saltwater interface, and the value analyzed by electrical conductivity can represent the current state of the freshwater-saltwater interface. Observed parameter was distributed on a virtual grid. The average of submarine fresh groundwater discharge fluxes for the virtual grid was determined as the watershed's representative flux. The submarine fresh groundwater discharge and flux distribution by year were also calculated at the basin scale. The method using electrical conductivity estimated the submarine fresh groundwater discharge from 2018 to 2020 to be 6.27 × 10⁶ m³/year; the method using the Ghyben-Herzberg ratio estimated a discharge of 10.87 × 10⁶ m³/year. The results presented in this study can be used as basis data for policies that determine sustainable water supply by using precise water budget analysis in coastal and island areas.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.5B
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• pp.459-469
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• 2010

This study is to develop a grid-based daily runoff model considering seasonal vegetation canopy condition. The model simulates the temporal and spatial variation of runoff components (surface, interflow, and baseflow), evapotranspiration (ET) and soil moisture contents of each grid element. The model is composed of three main modules of runoff, ET, and soil moisture. The total runoff was simulated by using soil water storage capacity of the day, and was allocated by introducing recession curves of each runoff component. The ET was calculated by Penman-Monteith method considering MODIS leaf area index (LAI). The daily soil moisture was routed by soil water balance equation. The model was evaluated for 930 $km^2$ Yongdam watershed. The model uses 1 km spatial data on landuse, soil, boundary, MODIS LAI. The daily weather data was built using IDW method (2000-2008). Model calibration was carried out to compare with the observed streamflow at the watershed outlet. The Nash-Sutcliffe model efficiency was 0.78~0.93. The watershed soil moisture was sensitive to precipitation and soil texture, consequently affected the streamflow, and the evapotranspiration responded to landuse type.