• Korean Journal of Agricultural and Forest Meteorology
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• v.9 no.4
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• pp.234-246
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• 2007

The role of macropore in the hydrological processes is important at the hillslope scale. Developments and distribution of macropores have not been investigated in conjunction with the characteristics of the hillslope such as topography, soil property, and soil moisture. In this study, macropore properties, such as macropore flow and saturation hydraulic conductivity were measured at a hillslope located in Gwangneung Research Forest, Pochun-gun, Gyeonggi-do, South Korea. An intensive field survey provided a refined Digital Elevation Model (DEM) for surface and subsurface topography. Spatial distributions of upslope area and topographic index were obtained through the digital terrain analysis. The total number of monitoring points was 22, and the selected points were distributed along the transect of the digital contour map. Vertical fluxes through macropores were measured using a tension infiltrometer at the depth of 0.1 m from the surface. Spatial and temporal distributions of soil moisture were obtained using an on-line measurement system, TRASE, installed in the study area. Soil moisture for the aforementioned points was measured at 0.1 and 0.3m depths below the surface. The results from tension infiltrometer experiments present that the macropore flows ranged between 21 and 94%, and the measured macroporosities varied from 1.4 to 47%. Macropore flows and macroporosities tended to increase as the measurement location moved to downslope. The ability for water conduction through macropores becomes increasingly developed as the location approaches the outlet of the hillslope.

• Proceedings of the Korea Water Resources Association Conference
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• 2009.05a
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• pp.971-975
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• 2009

본 연구에서는 격자강우량과 GIS와 연계한 격자기반의 공간수문자료들을 모형의 입력매개변수로 활용하고, 수계망을 통하여 유역 출구까지 운동파(kinematic wave)이론에 의해 유출량을 물리적으로 추적해 나가는 격자기반의 분포형 강우-유출모형인 K-DRUM(Kwater Distributed RUnoff Model)을 개발하였고, 지표유출량에 가장 큰 영향을 주지만 실제 관측 및 적용이 용이하지 않은 유역의 초기토양함수상태에 대한 자동보정기법을 개발하였다. 개발된 자동보정기법을 이용하여 남강댐유역을 대상으로 적용가능성을 평가하였다. 연구에서 사용한 강우사상은 남강댐 유역에 큰 영향을 준 태풍 루사 (2002년 8월 31일 01시$^{\sim}$9월1일 23시), 태풍 매미 (2003년 9월 12일 01시$^{\sim}$9월13일 23시), 2004년의 대류성강우 (2004년 7월14일 01시$^{\sim}$7월 16일 10시) 및 태풍 에위니아 (2006년 7월 8일 18시$^{\sim}$7월11일 12시)의 총 4개의 사상을 대상으로 하였다. 개발한 유역의 초기토양함수상태 자동보정기법에 의한 유출모의의 적용성을 검토하기 위하여 모의에 사용된 매개변수 중 토지피복도에 의해 결정되는 조도계수와 토양도에 의해 결정되는 유효토심, 흡인수두계수, 공극률 및 투수계수는 4개의 강우사상에서 모두 동일한 조건으로 설정하였고, 유역내 토양 내부 수분함유량 산정을 위한 초기 기저유출량은 검토대상 기간 시점부에서 관측된 유출량으로 설정하였다. 초기토양함수상태 자동보정기법 적용을 통한 유출해석의 정확도는 체적오차 백분율(VER)과 첨두 유량 오차 백분율(QER)을 이용하여 평가하였으며, 이를 통해 본 모형이 유출량에 대한 정확성을 확보하고자 하였다. 본 연구에서 개발된 자동보정 기법을 적용한 결과, 초기토양조건을 설정하는데 있어서 기존의 시행착오법으로 인해 소요되는 시간과 유역내 토양 특성과 지형형상을 고려하지 않는 설정으로 인해 발생될 수 있는 문제점을 해결할 수 있었으며, 유출계산 결과도 유량의 크기와 첨두시간 모두 관측값과 비교적 잘 맞는 것을 확인할 수 있었다.

• Korean Journal of Agricultural and Forest Meteorology
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• v.1 no.1
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• pp.29-35
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• 1999

Soil structure and organic matter have been known to strongly affect water flow and solute transport, yet little information is available concerning soil hydraulic properties related to soil physical and chemical properties in the forest site. The purpose of this study was to quantify the spatial variability and spatial correlation of the measured parameter values from the plots established with the rainfall simulator on Japanese larch(Larix leptolepis) dominated site in Kwangju. Kyunggi-Do. Measurement of soil water flux and retention were made with the inherent soil texture, soil structure, and organic matter. The method was based on the observation that when water was applied at a constant rate to the soil surface on each plot. The method was simple to apply and consists of following steps: (i) Wet the soil from a rainfall simulator with several known discharge rates on a relatively leveled soil surface with and without organic matter. (ii) Once the borders of the ponded zone were steady, saturated hydraulic conductivity( $K_{s}$) and the matric flux function(F) was evaluated from a regression of flux vs. the reciprocal of the ponded area. A conductivity of the form $K_{i+}$$_1$ $_{c}$= $K_{i}$( $_{c}$) [1-d /dz] where flux continuity implies. For this, continuity of matric potential at the interface at all times are as follows: $_1$( $Z_{c}$) = $_2$( $Z_{c}$) = $_{c}$ for steady state intake from water ponded on the soil surface. Results of this investigation showed the importance of understanding spatial variability in wide differences of water retention and saturated hydraulic conductivity with respect to pore geometry and organic matter contents which influenced the water flux throughout the soil profile.l profile.ile.

• Journal of Soil and Groundwater Environment
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• v.11 no.1
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• pp.65-76
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• 2006

This paper outlines the methodology of grid-based water balance for estimating the spatial distribution of recharge, which is applied to Woedo catchment in the northern area of the Jeju Island. The catchment is divided into grids and a daily water balance in each grid is computed for the period of 5 years. Daily rainfall data in each grid is interpolated from the data of 10 rainfall gauging stations. The spatial distributions of parameters such as SCS curve number, soil water retention capacity and crop coefficients are derived from GIS analyses of soil and land use characteristics. The SCS curve number is obtained by calibrating simulated runoffs with respect to the observed runoffs. The results show that the average annual rainfall increases from 1,665 mm/year to 3,382 mm/year in accordance with the topographic elevation, and the average annual recharge varies from 372 mm/year to 2,576 mm/year according to the average annual rainfall increases. Spatial variability of recharge is the highest among the water balance components such as rainfall, direct runoff, evaprotranspiration and recharge because the rate of runoff and evapotranspiration in the area with relatively low rainfall is higher than the other area.

• Journal of Korea Water Resources Association
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• v.36 no.6
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• pp.961-969
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• 2003

Formulation of quasi-dynamic wetness index was derived to predict the spatial and temporal distribution of the soil moisture. The algorithm of dynamic wetness index was developed through introducing the convolution integral with the rainfall input. The spatial and temporal behaviors of the wetness index of the Sulmachun Watershed was calculated using the digital elevation model(DEM) and the rainfall data for two years. The spatial distribution of the dynamic wetness index shows most dispersive feature of flow generation among the three assumptions of steady, quasi-dynamic and dynamic. The statistical distribution of the quasi-dynamic wetness index and the dynamic wetness index approximate to the steady state wetness index as the time step is increased. The dynamic wetness index shows mixed distribution of the normalized probability density function.

• Journal of Korean Society on Water Environment
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• v.32 no.1
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• pp.60-69
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• 2016

In this study, we estimated root zone soil moisture dynamics using remotely sensed (RS) data. A soil moisture data assimilation scheme was used to derive the soil and root parameters from MODerate resolution Imaging Spectroradiometer (MODIS) data. Based on the estimated soil/root parameters and weather forcings, soil moisture dynamics were simulated at spatio-temporal scales based on a hydrological model. For calibration/validation, the Little Washita (LW13) in Oklahoma and Chungmi-cheon/Seolma-cheon sites were selected. The derived water retention curves matched the observations at LW 13. Also, the simulated soil moisture dynamics at these sites was in agreement with the Time Domain Reflectrometry (TDR)-based measurements. To test the applicability of this approach at ungauged regions, the soil/root parameters at the pixel where the Seolma-cheon site is located were derived from the calibrated MODIS-based (Chungmi-cheon) soil moisture data. Then, the simulated soil moisture was validated using the measurements at the Seolma-cheon site. The results were slightly overestimated compared to the measurements, but these findings support the applicability of this proposed approach in ungauged regions with predictable uncertainties. These findings showed the potential of this approach in Korea. Thus, this proposed approach can be used to assess root zone soil moisture dynamics at spatio-temporal scales across Korea, which comprises mountainous regions with dense forest.

• Journal of the Korean earth science society
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• v.26 no.1
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• pp.93-105
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• 2005

Climatological characteristics in the variation of soil temperatures in Korea were investigated using Korea Meterological Administration's observation data. And the impacts of soil moisture on the variation of soil temperature were examined using observed precipitation data. The climatological averages of soil temperatures are ranged from 14.4 to $15.0^{\circ}C$ regardless of depths. And they showed an latitudinal gradient with a warm temperature at the southern region and 'U' shape as in the air temperature with a high value along the coastal region. The relatively higher heat capacity and low conductivity of soil compared to those of the air resulted in the significant delay of the maximum and minimum date with depth. As a results, soil acts as a heat source during winter while a heat sink during summer. Global warming and urban heat island have increased the soil temperatures with an average rate $0.3\~0.5^{\circ}C/10-year$ as in the air temperature during last 30 years $(1973\~2002)$. However, the warming rate is maximized during spring contrary to the winter in the air temperature. The temporal variation of soil temperatures is strongly affected by that of soil moisture through an modification of the heat capacity and heat convection. In general, the increased soil moisture clearly decreased the temporal variations and increased the deep layer soil temperatures during cold season.

• Korean Journal of Agricultural and Forest Meteorology
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• v.26 no.2
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• pp.127-139
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• 2024

Climate change has increased extreme weather events likewise heatwaves, heavy rain, and drought. Unlike other natural disaster, drought is a slowly developing phenomenon and thus drought damage increases as the drought continues. Therefore, it is necessary to understand the characteristics and mechanism of drought occurrence. Agricultural drought occurs when the water supply needed by crops becomes insufficient due to lack of soil water. Therefore, soil water is used as a key variable affecting agricultural drought. In this study, we examined the spatio-temporal distribution and trends of drought across the Korean Peninsula by determining the soil available water content (SAWC) through a model that integrated soil, meteorological, and crop data. Moreover, an investigation into the correlation between meteorological variables and the SAWC was conducted to assess how meteorological characteristics influence the nature of drought occurrences. During the soybean cultivation period, the average SAWC was lowest in 2018 at 88.6% and highest in 2021 at 103.2%. Analysis of the spatial distribution of SAWC by growth stage revealed that the lowest SAWC occurred during the flowering stage (S3) in 2018, during the leaf extension stage (S2) in 2019, during the seedling stage (S1) in 2020, again during the flowering stage (S3) in 2021, and during the seedling stage (S1) in 2022. Based on the average SAWC across different growth stages, the frequency of upland drought was the highest at 22 times during the S3 in 2018. The lowest SAWC was primarily influenced by a significant negative correlation with rainfall and evapotranspiration, whereas the highest SAWC showed a significant positive correlation with rainfall and relative humidity, and a significant negative correlation with reference evapotranspiration.

• Proceedings of the Korea Water Resources Association Conference
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• 2023.05a
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• pp.282-282
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• 2023

도시침수와 도시열섬 등 도시화 및 기후변화로 인한 물 및 환경문제에 대비하기 위해서는 고해상도 물순환 및 열순환 해석 기술이 필수적이다. 도심지의 고밀도 건축물 및 식생 등 다양한 토지피복의 조합은 물/열 순환에 직접적인 영향을 미치는 요인이며, 물리과정에 대한 이해를 높이기 위해서는 고해상도 모의 및 관측이 필요하다. WRF-Hydro는 침투 및 증발산, 열 순환, 지표와 하천 및 저수지 추적 등 여러 물/열 순환 요소 해석 모듈을 연동할 수 있는 공간분포형 수문 해석 시스템이다. 본 연구에서는 WRF-Hydro를 기반으로 낙동강 지류인 금호강 유역에 대한 고해상도 물순환 및 열순환 모형을 구축하여, 토양수분, 하천 유량, 지표온도, 증발산 등 수문 요소 해석 결과를 분석한다. WRF-Hydro 모형의 입력자료 구축 시 고해상도 토지피복 및 토양도를 적용하고, 기상자료에는 국내 지상관측자료와 국외 재분석자료를 비교, 분석하여 자료의 신뢰성을 분석한다. 또한, ECOSTRESS 등 고해상도 원격탐사자료로부터의 열, 증발산 관련 추정 자료를 모의 결과와 비교하여, 열순환 해석의 불확실성을 평가한다. 물순환과 열순환의 해석의 신뢰도를 동시에 향상하기 위한 분포형 모형의 구축 및 매개변수 보정 방안에 대해 토의한다.

• Horticultural Science & Technology
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• v.33 no.4
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• pp.605-617
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• 2015

The ultimate goal of this research is to develop a botanical biofiltration system that combines a green interior, biofiltering, and automatic irrigation to purify indoor air pollutants according to indoor space and the size of biofilter. This study was performed to compare the stability of air flow characteristics and removal efficiency (RE) of fine dust within a wall-typed (vertical) botanical biofilter depending on humidifying cycle and to investigate RE of volatile organic compounds (VOCs) by the biofilter. The biofilter used in this experiment was designed as an integral form of water metering pump, water tank, blower, humidifier, and multi-level planting space in order to be suitable for indoor space utilization. As a result, relative humidity, air temperature, and soil moisture content (SMC) within the biofilter showed stable values regardless of three different humidifying cycles operated by the metering pump. In particular, SMCs were consistently maintained in the range of 27.1-29.7% during all humidifying cycles; moreover, a humidifying cycle of operating for 15 min and pausing for 45 min showed the best horizontal linear regression (y = 0.0008x + 29.09) on SMC ($29.0{\pm}0.2%$) during 120 hour. REs for number of fine dust (PM10) and ultra-fine dust (PM2.5) particles passed through the biofilter were in the range of 82.7-89.7% and 65.4-73.0%, respectively. RE for weight of PM10 passed through the biofilter was in the range of 58.1-78.9%, depending on humidifying cycle. REs of xylene, ethyl benzene, total VOCs (TVOCs), and toluene passed through the biofilter were in the range of 71.3-75.5%, while REs of benzene and formaldehyde (HCHO) passed through the biofilter were 39.7% and 44.9%, respectively. Hence, it was confirmed that the wall-typed botanical biofilter suitable for indoor plants was very effective for indoor air purification.