• The Korean Journal of Ecology
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• v.23 no.2
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• pp.117-123
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• 2000

Changing patterns and the possibility of climate change in the area of Cheiudo island, the southernmost Island in Korea, were analyzed using daily temperature and Precipitation data observed at the Cheiu Regional Meteorological Office from May 1923 to December 1998. A hydrologic simulation model "BROOK" was used to simulate and analyze the dynamics of daily soil moisture content and soil moisture deficit by applying the daily weather data. During the period, significantly increasing pattern was observed in temperature data of both annual and monthly basis, while no significantly changing pattern was observed in precipitation data. During the last 76 years. mean annual temperature was observed to have risen about 1.4$^{\circ}C$, which may show the Possibility of the initiation of climate change on the island whose validity should be tested in future studies after long-term studies on temperature. Based on the simulation, due to increased temperature, significant increase was predicted in evapotranspiration. while no significant decrease was detected in simulated soil moisture content during the period. Changing pattern of annual soil moisture content was markedly different from those of precipitation. In some dominant trees, negative effects of the drought of the late season for the previous year were shown to be statistically significant to radial growth of the tree for the current year. As annual variation of radial growth of trees is mainly affected by the soil moisture content. the information on the dynamics of soil moisture deficit possibly provides us with useful information for the interpretation of tree growth decline on the mountain. mountain.

• Korean Journal of Plant Resources
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• v.13 no.2
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• pp.95-103
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• 2000

To study the effects of soil moisture and texture on characteristics of growth, content of saikosaponins and activity of antioxidative enzymes in Bupleurum falcatum L., content of saikosaponins(a, c and d) and activities of superoxide dismutase(SOD) and peroxidase(POD) were investigated with two Bupleurum genotypes(Jangsoo and Samdo). Two Bupleurum genotypes were grown under different soil moisture(deficit, normal, surplus) and soil texture(sandy, sandy loam, loam) conditions. Among the tested soil conditions, dry weight accumulation rate of both cultivars could be ranked in the order surplus > normal > deficit soil for soil moisture and sandy > sandy loam > loam for soil texture. Under the surplus soil condition, growth retardation of Samdo cultivar was more severer than that of Jangsoo. Furthermore, content of saikosaponin a, d, and c also could be ranked in the order deficit > normal > surplus and sandy > sandy loam > loam for soil moisture and texture, respectively. Although both Jangsoo and Samdo cultivars grown under water deficit condition showed the highest POD and SOD activity, in general POD and SOD activity in both shoot and root was remarkably high in Jangsoo cultivar compared with Samdo. Saikosaponin content of root was positively correlated with POD and SOD. However, shoot and root length were negatively correlated with POD.

• Water Engineering Research
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• v.1 no.3
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• pp.243-256
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• 2000

This physically-based hydrologic model is developed to calculate the soil-moisture balance on paddy fields. This model consists of three modules; the first is the unsaturated module, the second is the rice evapotranspiration module with SPAC(soil-plant-atmospheric-continuum), and the third is the groundwater and open channel flows based upon the interrehtionship module. The model simulates the hydrlogical processes of infiltration, soil water storage, deep perocolation or echarge to the shallow water table, transpiration and evaporation from the soil surface and also the interrelationship of the groundwater and river flow exchange. To verify the applicability of the developed model, it was applied to the Kimjae Plains, located in the center of the Dongjin river basin in Korea, during the most serious drought season of 1994. The result shows that the estimated water net requirement was 757mm and the water deficit was about 5.9% in this area in 1994. This model can easily evaluate the irrigated water quantity and visualize the common crop demands and soil moisture conditions.

• Journal of The Korean Society of Agricultural Engineers
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• v.59 no.1
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• pp.57-70
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• 2017

In this study, we evaluated daily root zone soil moisture dynamics and agricultural drought using a near-surface soil moisture data assimilation scheme with Soil Moisture Active & Passive (SMAP, $3km{\times}3km$) soil moisture footprints under different hydro-climate conditions. Satellite-based LANDSAT and MODIS image footprints were converted to spatially-distributed soil moisture estimates based on the regression model, and the converted soil moisture distributions were used for assessing uncertainties and applicability of SMAP data at fields. In order to overcome drawbacks of the discontinuity of SMAP data at the spatio-temporal scales, the data assimilation was applied to SMAP for estimating daily soil moisture dynamics at the spatial domain. Then, daily soil moisture values were used to estimate weekly agricultural drought based on the Soil Moisture Deficit Index (SMDI). The Yongdam-dam and Soyan river-dam watersheds were selected for validating our proposed approach. As a results, the MODIS/SMAP soil moisture values were relatively overestimated compared to those of the TDR-based measurements and LANDSAT data. When we applied the data assimilation scheme to SMAP, uncertainties were highly reduced compared to the TDR measurements. The estimated daily root zone soil moisture dynamics and agricultural drought from SMAP showed the variability at the sptio-temporal scales indicating that soil moisture values are influenced by not only the precipitation, but also the land surface characteristics. These findings can be useful for establishing efficient water management plans in hydrology and agricultural drought.

• Journal of The Korean Society of Agricultural Engineers
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• v.54 no.6
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• pp.19-28
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• 2012

This study carried out farmland suitability analysis for southern-type garlic cultivation considering soil and temperature as well as water deficit conditions. The spatial extent was limited within the area derived by Kim et al. (2012) using just soil and temperature constraints. Daily soil moisture was simulated using a one-layer soil water balance model at a $100{\times}100m$ grid unit, and then annual water deficit was calculated from 2000 to 2010. The farmland suitability was classified as four steps: best suitable, suitable, possible, and low productive. As a result, total area of best suitable or suitable farmland was about 375,900 ha, and Gimje-si and Haenam-gun were appeared as the largest favorable area for southern-type garlic cultivation. The best suitable or suitable area at Haenam-gun, Goheung-gun, Shinan-gun, Namhae-gun, and Muan-gun, major production regions of southern-type garlic, were extracted as 20,187 ha, 13,018 ha, 4,715 ha, 1,319 ha, and 349 ha, respectively. On the other hand, the result showed that the adoption of sprinkler irrigation systems might be critical in cultivating the southern-type garlic at some regions having poor water balance.

• Journal of the Korean Institute of Landscape Architecture
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• v.27 no.1
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• pp.122-131
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• 1999

Indoor environments are usually less than optimal for the growth of ferns, especially in regards to the water condition. These studies were performed to investigate responses involved in causing growth of ferns and presume management plan against the water deficit under indoor conditions. The effect of air humidity and soil moisture on the ferns was examined in Adiantume raddianum and Selaginella kraussiana. Results of experiments are as follows; 1. Under a low humidity condition, having a 25-50% RH. ornamental value of ferns decreased much more than under a 90% RH. Under a low soil moisture, such as sand treatment, ornamental value of ferns also decreased. 2. Leaf chlorophyll content, water content and stomata situations increased as air humidity and soil moisture went up. 3. Even if air humidity and soil water were not enough for ferns growth, the extending of irrigation cycle was helpful. 4. Under extremely low air humidity conditions, some water management, namely, using water holding soil or extending of irrigation cycle was desirable. Other methods of increasing air humidity, including water instruments such as ornamental pools, waterfalls, or fountains, grouping plants together were also helpful. But spraying water on leaves increased injury to ferns growth because of excess evaporation from the leaves. Though these studies, we learn that ferns are susceptible to water condition such as air humidity, soil water and water management. If other environmental factos are maintained with optimal conditions, water condition plays an important role in ferns growth in indoor environments.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.4B
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• pp.345-354
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• 2006

Drought brings on long term damage in contrast to flood, on economic loss in the region, and on ecologic and environmental disruptions. Drought is one of major natural disasters and gives a painful hardship to human beings. So we have tried to quantify the droughts for reducing drought damage and developed the drought indices for drought monitoring and management. The Palmer's drought severity index (PDSI) is widely used for the drought monitoring but it has the disadvanges and limitations in that the PDSI is estimated by considering just climate conditions as pointed out by many researchers. Thus this study uses the SWAT model which can consider soil conditions like soil type and land use in addition to climate conditions. We estimate soil water (SW) and soil moisture index (SMI) by SWAT which is a long term runoff simulation model. We apply the SWAT model to Soyang dam watershed for SMI estimation and compare SMI with PDSI for drought analysis. Say, we calibrate and validate the SWAT model by daily inflows of Soyang dam site and we estimate long term daily soil water. The estimated soil water is used for the computation of SMI based on the soil moisture deficit and we compare SMI with PDSI. As the results, we obtained the determination coefficient of 0.651 which means the SWAT model is applicable for drought monitoring and we can monitor drought in more high resolution by using GIS. So, we suggest that SMI based on the soil moisture deficit can be used for the drought monitoring and management.

• Proceedings of the Korea Water Resources Association Conference
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• 2005.09a
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• pp.184-185
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• 2005

• Journal of The Korean Society of Agricultural Engineers
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• v.60 no.4
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• pp.73-82
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• 2018

In this study, we assessed meteorological and agricultural drought based on the SPI(Standardized Precipitation Index), SMP(Soil Moisture Percentile), and SMDI(Soil Moisture Deficit Index) indices using satellite-based TRMM(Tropical Rainfall Measuring Mission)/GPM(Global Precipitation Measurement) images at the province of Chungcheongbuk-do. The long-term(2000-2015) TRMM/GPM precipitation data were used to estimate the SPI values. Then, we estimated the spatially-/temporally-distributed soil moisture values based on the near-surface soil moisture data assimilation scheme using the TRMM/GPM and MODIS(MODerate resolution Imaging Spectroradiometer) images. Overall, the SPI value was significantly affected by the precipitation at the study region, while both the precipitation and land surface condition have influences on the SMP and SMDI values. But the SMP index showed the relatively extreme wet/dry conditions compared to SPI and SMDI, because SMP only calculates the percentage of current wetness condition without considering the impacts of past wetness condition. Considering that different drought indices have their own advantages and disadvantages, the SMDI index could be useful for evaluating agricultural drought and establishing efficient water management plans.

• Journal of The Korean Society of Agricultural Engineers
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• v.65 no.3
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• pp.57-67
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• 2023

A flash drought is a rapid-onset drought that develops over a short period of time as weather and environmental factors change rapidly, unlike general droughts, due to meteorological abnormalities. Abnormally high evapotranspiration rates and rapid declines in soil moisture increase vegetation stress. In addition, crop yields may decrease due to flash droughts during crop growth and may damage agricultural and economic ecosystems. In this study, Flash Drought Intensity Index (FDII) based on soil moisture data from Gravity Recovery Climate Experiment (GRACE) was used to analyze flash drought. FDII, which is calculated using soil moisture percentile, is expressed by multiplying two factors: the rate of intensification and the drought severity. FDII was developed for domestic flash drought events from 2014 to 2018. The flash drought that occurred in 2018, Chungcheongbuk-do showed the highest FDII. FDII was higher in heat wave flash drought than in precipitation deficit flash drought. The results of this study show that FDII is reliable flash drought analysis tool and can be applied to quantitatively analyze the characteristics of flash drought in South Korea.