임성훈 Eam Sung Hoon

DOI: JKWST Vol.57(No.1) 1-9, 2015

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In this study it was adopted on sea dike monitoring that the safety monitoring with statistical limits which was adapted usually on safety monitoring by measuring pressures, stresses or deformations. And also the hydraulic head loss rate change according to passage of time was calculated for the purpose of safety monitoring. Safety monitoring by setting the statistical limit on the measured pore water pressure graphs need to be supplemented with an additional method of monitoring because the difference between the rise and fall of the tide was irregular. Safety monitoring by the limits set from values predicted by linear regression and standard errors on the hydraulic head loss graph was not affected by irregularity of tide. But if the condition of an embankment is changed gradually and slowly, it will not be detected on the hydraulic head loss graph. The graph of hydraulic head loss rate for every 24 hours vs date showed clearly that the sea water blocking state was getting better or not even though it was changed gradually and slowly.

임성훈 Eam Sung Hoon

DOI: JKWST Vol.57(No.1) 11-23, 2015

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In this study the laboratory test for hydraulic conductivity and the seepage analysis with finite element method on measurement section of sea dike embankment were performed for the purpose of estimating the relative density of embankment from the measured pore water pressures, and both results of the test and the analysis were coupled with the method of estimating seepage blocking state with the hydraulic head loss rate in sea dike embankment. The relationship of void ratio vs hydraulic head loss rate was obtained by setting hydraulic conductivity as common ordinate on the relationships between the void ratio and the hydraulic conductivity and between the hydraulic conductivity and the hydraulic head loss rate. The void ratio on the segment between measuring points was calculated from the coupled relationship of the void ratio vs the hydraulic conductivity. The allowable upper and lower limits of hydraulic head loss rate and those of void ratio on the safety were generated from the coupled relationship between the laboratory compaction test and the sedimentation test. Current hydraulic head loss rate and void ratio were evaluated in the allowable range between upper and lower limits.

홍은미 Hong Eun-mi , 최진용 Choi Jin-yong , 남원호 Nam Won-ho , 이상현 Lee Sang-hyun , 유승환 Yoo Seung-hwan

DOI: JKWST Vol.57(No.1) 25-35, 2015

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As livestock manure treatment is becoming a problem, manure application in forest plantation is recommended as an alternative. In this study, to investigate the impact due to liquid manure application in forest plantation, soil, soil water and shallow groundwater quality had been monitored in poplar experimental site where the liquid manure (LM) was applied. Water samples were collected weekly during growing season (April to October) from 2008 to 2011. From the monitoring results, phosphorus concentration in the soil and soil water had no significant difference between LM and control plots. NO₃-N concentration of soil water in LM, however, showed higher concentration (13.6 mg/l at 40 cm, 35.1 mg/l at 80 cm) than control plot (1.5 mg/l at 40 cm, 0.5 mg/l at 80 cm). In case of shallow groundwater quality, pH, heavy metal, etc. were satisfied to the national agricultural water quality standard of groundwater and there were no significant difference between upstream and downstream. The NO₃-N concentration of shallow groundwater was also not exceeded the national drinking water standard. However, NO₃-N concentration in soil water and downstream of shallow groundwater had increased in 2011 when non-composted LM was applied mostly in non-growing season of tree (September). From the results, it is important to control nitrogen source, application time and decomposed or not when LM is applied. In addition, to investigate nitrate source, further long-term monitoring and modelling could be necessary.

남원호 , Michael J. Hayes , Donald A. Wilhite , Mark D. Svoboda

DOI: JKWST Vol.57(No.1) 37-45, 2015

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Recent droughts in South Korea have had large economic and environmental impacts across the country. Changes in rainfall and hydrologic patterns due to climate change can potentially increase the occurrence of extreme droughts and affect the future availability of water resources. Therefore, it is necessary to evaluate drought vulnerability for water resources planning and management, and identify the appropriate mitigation actions to conduct a drought risk analysis in the context of climate change. The objective of this study is changes in the temporal trends of drought characteristics in South Korea to examine drought impacts under climate change. First, the changes of drought occurrence were analyzed by applying the Standardized Precipitation Evapotranspiration Index (SPEI) for meteorological data on 54 meteorological stations, and were analyzed for the past 30 years (1981-2010), and Representative Concentration Pathways (RCP) climate change scenarios (2011-2100). Second, the changes on the temporal trends of drought characteristics were performed using run theory, which was used to compare drought duration, severity, and magnitude to allow for quantitative evaluations under past and future climate conditions. These results show the high influence of climate change on drought phenomenon, and will contribute to water resources management and drought countermeasures to climate change.

류정훈 Ryu Jeong Hoon , 강문성 Kang Moon Seong , 송인홍 Song Inhong , 박지훈 Park Jihoon , 송정헌 Song Jung-hun , 전상민 Jun Sang Min , 김계웅 Kim Kyeung

DOI: JKWST Vol.57(No.1) 47-57, 2015

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Along with climate change, the occurrence and severity of natural disasters have been increased globally. In particular, the increase of localized heavy rainfalls have caused severe flood damage. Thus, it is needed to consider climate change into the estimation of design flood, a principal design factor. The main objective of this study was to estimate design floods for an agricultural reservoir watershed based on the RCP (Representative Concentration Pathways) scenarios. Gyeryong Reservoir located in the Geum River watershed was selected as the study area. Precipitation data of the past 30 years (1981 ∼2010; 1995s) were collected from the Daejeon meteorological station. Future precipitation data based on RCP2.6, 4.5, 6.0, 8.5 scenarios were also obtained and corrected their bias using the quantile mapping method. Probability rainfalls of 200-year frequency and PMPs were calculated for three different future spans, i.e. 2011∼2040; 2025s, 2041∼2070; 2055s, 2071∼2100; 2085s. Design floods for different probability rainfalls were calculated using HEC-HMS. As the result, future probability rainfalls increased by 9.5 %, 7.8 % and 22.0 %, also design floods increased by 20.7 %, 5.0 % and 26.9 %, respectively, as compared to the past 1995s and tend to increase over those of 1995s. RCP4.5 scenario, especially, resulted in the greatest increase in design floods, 37.3 %, 36.5 % and 47.1 %, respectively, as compared to the past 1995s. The study findings are expected to be used as a basis to reduce damage caused by climate change and to establish adaptation policies in the future.

남원호 , 김태곤 , 홍은미 , Michael J. Hayes , Mark D. Svoboda

DOI: JKWST Vol.57(No.1) 59-67, 2015

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Because reservoirs that supply irrigation water play an important role in water resource management, it is necessary to evaluate the vulnerability of this particular water supply resource. The purpose of this study is to provide water supply risk maps of agricultural reservoirs in South Korea using irrigation vulnerability model and cluster analysis. To quantify water supply risk, irrigation vulnerability indices are estimated to evaluate the performance of the water supply on the agricultural reservoir system using a probability theory and reliability analysis. First, the irrigation vulnerability probabilities of 1,346 reservoirs managed by Korea Rural Community Corporation (KRC) were analyzed using meteorological data on 54 meteorological stations over the past 30 years (1981-2010). Second, using the K-mean method of non-hierarchical cluster analysis and pre-simulation approach, cluster analysis was applied to classify into three groups for characterizing irrigation vulnerability in reservoirs. The morphology index, watershed area, irrigated area, and ratio between watershed and irrigated area are selected as the clustering analysis parameters. It is suggested that the water supply risk map be utilized as a basis for the establishment of risk management measures, and could provide effective information for a reasonable decision making on drought risk mitigation.

송정헌 Song Jung Hun , 송인홍 Song Inhong , 김진택 Kim Jin-taek , 강문성 Kang Moon Seong

DOI: JKWST Vol.57(No.1) 69-78, 2015

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The objective of this study was to investigate characteristics of irrigation return flow from paddy block in a reservoir irrigated district during growing seasons. The irrigation return flow was divided into three parts, quick return flow from irrigation canal (RFI), quick return flow from drainage canal (RFD), and delayed return flow (DRF). The RFI was calculated from water level and stage-discharge relationships at the ends of the irrigation canals. The DRF was estimated using measured infiltration amount from paddy fields of the irrigated district. A combined monitoring and modeling method was used to estimate the RFD by subtracting surface runoff from surface drainage. The paddy block irrigated from the Idong reservoir was selected to study the irrigation return flow components. The results showed that daily agricultural water supply (AWS), the RFI, and the RFD were 27.4 mm day^-1, 4.9 mm day-1, and 19.8 mm day^-1, respectively in May, which were greater than other months (p<0.05). The return flow ratio of the RFI and the RFD were the greatest in July (34.6%) and May (72.3%), respectively. The daily AWS was closely correlated with the RFD (correlation coefficients of 0.76~0.86) in except for July with, while correlation coefficient with the RFI were 0.56 and 0.42 in June and July, respectively (p<0.01). The total irrigation return flow was 1,965 mm in 2011, and 1,588 mm in 2012, resulting in total return flow ratio of 84.6% and 79.1%, respectively. This results indicate that substantial amounts of agricultural water were returned to streams as irrigation return flow. Thus, irrigation return flow should be fully considered into the agricultural water resources planning in Korea.

홍성구 Hong Seong-gu

DOI: JKWST Vol.57(No.1) 79-87, 2015

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A thermochemical equilibrium model was constructed for predicting composition of synthesis gas in biomass gasification. The model included estimation of equilibrium constants using Gibbs free energy. After constructing the model, the results were compared with the experimental values and predictions from a previous model. Gas compositions were reasonably well agreed with them and showed effects of operational and fuel condition. When the reaction temperature increased, the lower heating values decreased due to the decrease in CH4 concentrations. The methane concentrations were lower than those observed in experimental results. The model was used to predict the gas composition and heating values for the cases of mixed fuel of charcoal and un-dry woodchips. Although downdraft gasifiers require fuels less than 15% of moisture contents, the model results indicated that the mixed fuel with charcoal and woodchips which had over 25% of moisture contents could be used in the downdraft gasifiers. It might be explained by increase in energy density resulting from mixing charcoal. The results imply that the efforts and costs for drying biomass fuels could be reduced by mixing charcoal or fuels with higher calorific values.

장선숙 Jang Sun Sook , 안소라 Ahn So Ra , 최중대 Choi Joong Dae , 김성준 Kim Seong Joon

DOI: JKWST Vol.57(No.1) 89-97, 2015

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This study is to assess the effect of non-point source pollution discharge loads between tillage and no-tillage applications for upland crop areas using SWAT (Soil and Water Assessment Tool) watershed modeling. For Byulmi-cheon small rural catchment (1.17 km²) located in upstream of Gyeongan-cheon watershed, the rainfall, discharge and stream water quality have been monitored in the catchment outlet since 2011. The SWAT model was calibrated and validated in hourly basis using 19 rainfall events during 2011-2013. The average Nash-Sutcliffe model efficiency and R² (determination coefficient) for streamflow were 0.67 and 0.79 respectively. Using the 10 % surface runoff reduction from experiment results for no-tillage condition in field plots of 3 % and 8 % slopes under sesami cultivation, the soil saturated hydraulic conductivity for upland crop areas was adjusted from 0.001 mm/hr to 0.0025 mm/hr in average. Under the condition, the catchment sediment, T-N (total nitrogen, TN), and T-P (total phosphorus, TP) discharge loads were reduced by 6.9 %, 7.4 %, and 7.7 % respectively.

노수각 Noh Soo-kack , 손영환 Son Young-hwan , 박재성 Park Jae-sung , 봉태호 Bong Tae-ho

DOI: JKWST Vol.57(No.1) 99-109, 2015

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In the construction industry, the interest for recycling aggregates is rising as more people demand for alternatives due to lack of supply of natural aggregates and environmental problems. However, in order for recycled aggregates to be used in infrastructures, stability and other factors need to be verified. Therefore, the objective of this study is to analyze the sensitivity of soil properties to secure slope safety according to various heights of embankment when bottom ash and dredged soil mixture is applied in the embankment. In most cases, all heights were safe for the slide for the embankment whether the water level is full or sudden draw down. The result of the sensitivity analysis revealed that the unit weight of embankments is highest among all factors to be considered. However, the sensitivity of the unit weight became smaller and the sensitivity of the friction angle of embankments increased with the height of embankments. The sensitivity of factors of core materials is very small because the core has weaker physical properties than those of the embankment. The effect of the height for each factor is different for each slope and water levels. The sensitivity of the unit weight of embankments is most affected when the height is 60m in the upstream slope. To conclude, bottom ash and dredged soil mixture can be applied in the embankment and different factors must be considered in different scale because the sensitivity depends highly on the height of embankments.

박성용 Park Sung-yong , 박덕환 Park Duck-hwan , 김현선 Kim Hyun-sun , 김정면 Kim Jung-myeon , 임현택 Lim Hyun-taek , 배수빈 Bae Su-bin , 김용성 Kim Yong-seong

DOI: JKWST Vol.57(No.1) 111-118, 2015

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This research aims to utilize lapilli from the Mt. Baekdusan as environmently-friendly construction material. First of all, the neutralizing method for fabricating lapilli-cement-mixed bioblock was examined. And then, by use of the neuralized bioblock with microorganism for water purification, the growth inhibition effect against the pathogenic coliform bacillus was evaluated. The result regarding growth inhibition effect on pathogenic coliform bacillus indicates that the pretreatment condition, which is a concurrent procession with aqueous solution of 10% di-ammonium Phosphate after water curing, led to pH degraded below 10 which was the target value. Therefore it was concluded that the method was effective on bio-block neutralization. The microorganisms purifying water and di-ammonium phosphate were detected through the examination for microorganism existence on the bioblock, therefore it was concluded that the bioblock composed of lapilli and cement is able to be utilized in various structures as an environment friendly construction material.