• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.2
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• pp.601-610
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• 2020

Recently, damage caused by drought is becoming worse and worse due to the global climate change. To overcome these problems, movable-weir to control the water level has been installed instead of a fixed-weir made from concrete. On the other hand, it is difficult to operate an existing moveable-weir because of the high cost of facility management and manpower consumption. In addition, because most moveable-weirs are installed in power systems, the operating cost and the cost of connection for power systems increase when they are located in remote areas. Therefore, this paper proposes an optimal design algorithm and the evaluation algorithm of the SOC (state of charge) of a lithium-ion battery to replace an existing power supply with eco-friendly movable-power with a power supply system using PV modules and lithium-ion batteries. In addition, this study modeled a 50kW power supply system of a movable-weir using PSCAD/EMTDC S/W. The simulation results confirmed that the proposed algorithm has stable operation characteristics in an independent operation mode and interconnection operation mode and that there is the possibility of commercialization with a benefits evaluation of the eco-friendly power supply system of a movable-weir.

• Journal of Korea Water Resources Association
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• v.43 no.3
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• pp.295-308
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• 2010

As an attempt to explore the impact of droughts which may be worse by the climate change, the change in the water balance of the Han-river basin is analyzed. To accomplish it, we suggest a procedure consisting of three successive sub-procedures: daily rainfall generation for 70 years by the RegCM3 RCM ($27{\times}27\;km$) with the A2 scenario, daily discharge simulations by SLURP using the generated daily rainfall data, and monthly water balance analysis by K-WEAP (Korean Water Evaluation and Planning System) based on the SLURP simulation. Since significant uncertainty is involved in forecasting the future water consumption and water yields, we assumed three water consumption scenarios and fifty water yields scenarios. Three water consumption scenarios are, namely, "LOW", "MEDIUM", and "HIGH" according to the expected amount of water consumption. The fifty daily discharges are obtained from the SLURP simulations during the drought period. Finally, water balance analysis is performed by K-WEAP based on 150 combinations from three water consumption scenarios and the fifty daily discharges. Analysis of water scarcity in small basins of the Han River basin showed concentration of water scarcity in some small basins. It was also found that water scarcity would increase in all small basins of the Han River basin.

• Korean Journal of Ichthyology
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• v.34 no.4
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• pp.262-269
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• 2022

A distribution survey was conducted from 2018 to 2020 to evaluate the distribution status, habitat characteristics, and extinction threat of the short ninespine stickleback Pungitius kaibarae (Gasterosteidae). Literature reports of P. kaibarae distribution have been sorted by each period, 1980~1996, 1997~2005, and 2007~2017, and the samples were collected in 32, 43, and 64 stations for each period. Among the 75 streams and 193 sampling sites investigated during the study period, 1,400 P. kaibarae individuals were collected from 26 streams at 39 sites. The main habitat of P. kaibarae was downstream or brackish water zones with a low altitude, slow water velocity, and many aquatic plants. The main reasons for the decline in population size were assumed to be drought and flood, river work for flood restoration and river maintenance, bridges construction, and predation by the exotic fish species Micropterus salmoides. Previous evidence reported a 42.6% reduction in occupancy within 10 years, a decline in habitat quality, and the spread and impact of the exotic fish species Micropterus salmoides. Therefore, P. kaibarae is now considered a Vulnerable (VU A2ace) species based on the IUCN Red List categories and criteria. Therefore, P. kaibarae should be redesignated as an endangered species by the Ministry of Environment and systematically managed.

• Korean Journal of Environment and Ecology
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• v.28 no.3
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• pp.357-364
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• 2014

This study aimed to determine effects of the use of water-retention additive, hydrophilic polymer, for extensive green roofs on growth of Juniperus chinensis var. sargentii and Euonymus fortunei 'Emerald and Gold' for woody plants, and Carex kobomugi and Carex pumila for herbaceous plants. Five different contents of hydrophilic polymer including 0% (Control), 1.0%, 2.5%, 5.0%, and 10% (polymer: medium (w/w), dry weight basis) were added to each of the container filed with a 100 kg of growth medium. Ten of plants were transplanted in each of square container ($1m(L){\times}1m(W){\times}0.3m$ (H)) built on the roof platforms in randomized complete block design in the $20^{th}$ of May, 2013. In results, excessively high volumetric soil water content, about 97-98%, was found in the substrate under elevated hydrophilic polymer concentration of at least 2.5%, during the entire growing period. The moisture content of the substrate containing 1.0% of hydrophilic polymer was higher about 20% in the range between 70% and 80%, compared tho that of Control substrate in the range between 50% and 60%, for 27 days after transplanting prior to abundant rainfall, indicating that the application of hydrophilic polymer to the extensive green roof substrate is effective to eliminate drought condition by retaining water in the substrate. Euonymus fortunei 'Emerald and Gold' and Carex kobomugi resulting in higher plant growth with 2.5% than those of the other treatment plants. Juniperus chinensis var. sargentii was observed the highest growth under 1.0% hydrophilic polymer treatement, and Carex pumila was founded the best growth with Control respectively. Plants that grown in both the 1.0% and 2.5% hydrophilic polymer survived all, while the plants that grown in the 5.0% and 10% hydrophilic polymer died after 3 months. These results suggest that advantage of the addition of hydrophilic polymer may be greater in drought-tolerant plants, but the mixture proportion of hydrophilic polymer should be determined according to the different features of the plant species being grown.

• Journal of the Korean Association of Geographic Information Studies
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• v.23 no.2
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• pp.53-69
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• 2020

The increase of the impermeable area due to industrialization and urban development distorts the hydrological circulation system and cause serious stream drying phenomena. In order to manage this, it is necessary to develop a technology for impact assessment of stream drying phenomena, which enables quantitative evaluation and prediction. In this study, the cause of streamflow reduction was assessed for dam and weir watersheds in the five major river basins of South Korea by using distributed hydrological model DrySAT-WFT (Drying Stream Assessment Tool and Water Flow Tracking) and GIS time series data. For the modeling, the 5 influencing factors of stream drying phenomena (soil erosion, forest growth, road-river disconnection, groundwater use, urban development) were selected and prepared as GIS-based time series spatial data from 1976 to 2015. The DrySAT-WFT was calibrated and validated from 2005 to 2015 at 8 multipurpose dam watershed (Chungju, Soyang, Andong, Imha, Hapcheon, Seomjin river, Juam, and Yongdam) and 4 gauging stations (Osucheon, Mihocheon, Maruek, and Chogang) respectively. The calibration results showed that the coefficient of determination (R²) was 0.76 in average (0.66 to 0.84) and the Nash-Sutcliffe model efficiency was 0.62 in average (0.52 to 0.72). Based on the 2010s (2006~2015) weather condition for the whole period, the streamflow impact was estimated by applying GIS data for each decade (1980s: 1976~1985, 1990s: 1986~1995, 2000s: 1996~2005, 2010s: 2006~2015). The results showed that the 2010s averaged-wet streamflow (Q95) showed decrease of 4.1~6.3%, the 2010s averaged-normal streamflow (Q185) showed decreased of 6.7~9.1% and the 2010s averaged-drought streamflow (Q355) showed decrease of 8.4~10.4% compared to 1980s streamflows respectively on the whole. During 1975~2015, the increase of groundwater use covered 40.5% contribution and the next was forest growth with 29.0% contribution among the 5 influencing factors.

• Proceedings of the Korean Society of Crop Science Conference
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• 2017.06a
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• pp.8-9
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• 2017

Soybean yield has been low and unstable in Japan and other areas in East Asia, despite long history of cultivation. This is contrasting with consistent increase of yield in North and South America. This presentation tries to describe perspective of breaking stagnation of soybean yield in East Asia, considering the factors of the different yields between regions. Large amount of rainfall with occasional dry-spell in the summer is a nature of monsoon climate and as frequently stated excess water is the factor of low and unstable soybean yield. For example, there exists a great deal of field-to-field variation in yield of 'Tanbaguro' soybean, which is reputed for high market value and thus cultivated intensively and this results in low average yield. According to our field survey, a major portion of yield variation occurs in early growth period. Soybean production on drained paddy fields is also vulnerable to drought stress after flowering. An analysis at the above study site demonstrated a substantial field-to-field variation of canopy transpiration activity in the mid-summer, but the variation of pod-set was not as large as that of early growth. As frequently mentioned by the contest winners of good practice farming, avoidance of excess water problem in the early growth period is of greatest importance. A series of technological development took place in Japan in crop management for stable crop establishment and growth, that includes seed-bed preparation with ridge and/or chisel ploughing, adjustment of seed moisture content, seed treatment with mancozeb+metalaxyl and the water table control system, FOEAS. A unique success is seen in the tidal swamp area in South Sumatra with the Saturated Soil Culture (SSC), which is for managing acidity problem of pyrite soils. In 2016, an average yield of $2.4tha^{-1}$ was recorded for a 450 ha area with SSC (Ghulamahdi 2017, personal communication). This is a sort of raised bed culture and thus the moisture condition is kept markedly stable during growth period. For genetic control, too, many attempts are on-going for better emergence and plant growth after emergence under excess water. There seems to exist two aspects of excess water resistance, one related to phytophthora resistance and the other with better growth under excess water. The improvement for the latter is particularly challenging and genomic approach is expected to be effectively utilized. The crop model simulation would estimate/evaluate the impact of environmental and genetic factors. But comprehensive crop models for soybean are mainly for cultivations on upland fields and crop response to excess water is not fully accounted for. A soybean model for production on drained paddy fields under monsoon climate is demanded to coordinate technological development under changing climate. We recently recognized that the yield potential of recent US cultivars is greater than that of Japanese cultivars and this also may be responsible for different yield trends. Cultivar comparisons proved that higher yields are associated with greater biomass production specifically during early seed filling, in which high and well sustained activity of leaf gas exchange is related. In fact, the leaf stomatal conductance is considered to have been improved during last a couple of decades in the USA through selections for high yield in several crop species. It is suspected that priority to product quality of soybean as food crop, especially large seed size in Japan, did not allow efficient improvement of productivity. We also recently found a substantial variation of yielding performance under an environment of Indonesia among divergent cultivars from tropical and temperate regions through in a part biomass productivity. Gas exchange activity again seems to be involved. Unlike in North America where transpiration adjustment is considered necessary to avoid terminal drought, under the monsoon climate with wet summer plants with higher activity of gas exchange than current level might be advantageous. In order to explore higher or better-adjusted canopy function, the methodological development is demanded for canopy-level evaluation of transpiration activity. The stagnation of soybean yield would be broken through controlling variable water environment and breeding efforts to improve the quality-oriented cultivars for stable and high yield.

• Journal of The Korean Society of Grassland and Forage Science
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• v.39 no.2
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• pp.105-113
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• 2019

A two-year study was conducted from 2017 to 2018 by the establishment of a test field at Chungju-si and Cheongyang-gun. Plant height, number of leaves, insects and diseases, and fresh and dry matter yields for corn hybrid('Kwangpyeongok') were investigated. Daily average, maximum, and minimum temperature, monthly average temperature, daily precipitation, and sunshine duration during the growing season were investigated. We selected climate-critical factors to corn productivity and conducted an evaluation of vulnerability to climate change from 1999 to 2018 for both regions. In 2018, the dry matter yield of forage corn was 6,475 and 7,511 kg/ha in Chungju and Cheongyang, respectively, which was half of that in 2017. The high temperature and drought phenomenon in the 2018 summer caused the corn yield to be low. As well as temperature, precipitation is an important climatic factor in corn production. As a result of climate impact vulnerability assessment, the vulnerability has increased recently compared to the past. It is anticipated that if the high temperature phenomenon and drought caused by climate change continues, a damage in corn production will occur.

• Journal of Korea Water Resources Association
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• v.55 no.11
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• pp.923-929
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• 2022

The Chuncheon Mullori area is an underprivileged area of water welfare where local water supply is not supplied, and it is supplying water to the villages with small water supply facilities using lateral flow and groundwater as water sources. This is an area with poor water supply conditions, such as relying on water trucks due to water shortages during the recent severe drought. Therefore, in order to solve the problem of water shortage during drought and to prepare for the increasing water demand, a sand dam was installed along the valley, and this facility has been operating since May 2022. In this study, repeated simulations were performed according to the hydraulic conductivity of the filler material and the storage coefficient value for the inflow condition for about two years from mid-March 2020 to mid-March 2022. For each case, the amount of discharge through the perforated drain pipe was calculated. Overall, as the hydraulic conductivity increased, the amount of discharge and its ratio increased. However, when the hydraulic conductivity of the second floor was relatively low, the amount of discharge increased and then decreased as the hydraulic conductivity of the third floor increased. This is considered to be due to the fact that the water level was kept low due to the rapid drainage compared to the net inflow into the third floor because the water permeability of the third floor and the drainage coefficient of the drain pipe were large. As a result of simulating the flow of the open channel in the upper part of the sand dam as a hypothetical groundwater layer with very high hydraulic conductivity, the decrease in discharge rate was slower than the increase in the hydraulic conductivity of the hypothetical layer, but it was clearly shown that the discharge volume decreased relatively as the hydraulic conductivity of the virtual layer increased.

• Journal of Korea Water Resources Association
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• v.49 no.12
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• pp.1027-1034
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• 2016

One of the most important purpose of multi-purpose reservoir is storing a large amount of water for utilization in a dry season. However, multi-purpose reservoirs that were constructed according to the limited hydrologic information available at the time of construction may encounter problems such as decreased water inflow due to climate change and an inability to cope with a water shortage. To solve these problems, in 2015, the Ministry of Land, Infrastructure and Transport suggested a revised water supply standard in case of water shortage for reservoirs. However, the revised standard has not been sufficiently discussed to determine its effectiveness. In addition, multi-purpose reservoirs in South Korea have secured and stored water for emergencies, but there is currently no way to utilize the stored water. Determining how to utilize the stored water effectively may be a useful method for preparing drought. Therefore, this article discusses the revised water supply standard as it relates to a water shortage in reservoirs and a method of utilizing the water stored for emergencies in multi-purpose reservoirs. The options for utilizing the water storage were evaluated using a water shortage safety degree index, and the results showed that the options may slightly and limitedly increase the water supply capacity. However, the evaluation also showed that a complex application of two options may overcome the exisiting problem and to supply water more effectively.

• Journal of Korea Water Resources Association
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• v.50 no.7
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• pp.489-502
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• 2017

The objective of this study is to propose and evaluate the BAYES-ESP, which is a dam inflow prediction method based on Ensemble Streamflow Prediction method (ESP) and Bayesian theory. ABCD rainfall-runoff model was used to predict monthly dam inflow. Monthly meteorological data collected from KMA, MOLIT and K-water and dam inflow data collected from K-water were used for the model calibration and verification. To estimate the performance of ABCD model, ESP and BAYES-ESP method, time series analysis and skill score (SS) during 1986~2015 were used. In time series analysis monthly ESP dam inflow prediction values were nearly similar for every years, particularly less accurate in wet and dry years. The proposed BAYES-ESP improved the performance of ESP, especially in wet year. The SS was used for quantitative analysis of monthly mean of observed dam inflows, predicted values from ESP and BAYES-ESP. The results indicated that the SS values of ESP were relatively high in January, February and March but negative values in the other months. It also showed that the BAYES-ESP improved ESP when the values from ESP and observation have a relatively apparent linear relationship. We concluded that the existing ESP method has a limitation to predict dam inflow in Korea due to the seasonality of precipitation pattern and the proposed BAYES-ESP is meaningful for improving dam inflow prediction accuracy of ESP.