권순국 Kwun Soon-kuk , 송인홍 Song In-hong , 피터월러 Waller Peter. M. , 최연식 Choi C. Yeonsik

DOI: JKWST Vol.49(No.2) 3-13, 2007

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The primary objective of this study was to compare water use efficiencies between subsurface drip irrigation and furrow irrigation. The uniformity of used drip lines was tested to determine if clogging would be a threat to the long-term success of a subsurface drip irrigation system. Three crops, cantaloupe, lettuce, and bell pepper, were grown in four plots for each irrigation system. Significantly less water was applied with subsurface drip irrigation than with furrow irrigation (29.5 % less for cantaloupe and 43.2 % less for bell pepper) in order to produce similar crop yields. Water use efficiencies with subsurface drip irrigation were significantly higher than those with furrow irrigation for cantaloupe (P-value = 0.018) and bell pepper (P- value ≤ 0.001). Drip-irrigated lettuce, a shallow-rooted crop, had moderately higher water use efficiency during the first two seasons, while no difference was observed in the third season. After the experiment, the uniformity of the drip lines was 92.1 % on average and classified as good. The high values for water use efficiency and uniformity indicate that subsurface drip irrigation can be a sustainable method for conserving irrigation water.

전계원 Jun Kye Won , 이호진 Lee Ho Jin

DOI: JKWST Vol.49(No.2) 17-24, 2007

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This study analyzes the flood inundation in low agricultural area caused by rainfall during typhoon periods and how flood inundation areas should be affected. GIS techniques, HEC-HMS and HEC-GeoHMS were used for flood runoff, HEC-RAS was applied in water surface elevation analysis at each cross-section. RMA2, SED2D were applied for runoff characteristics of inundation areas and river bed change and distribution of sediment. As a result, velocity distribution was analyzed 2.6 m/s-3.4 m/s in flood inundation by water level increase. In the case of bed elevation change, most sediments were deposited to the parts that adjoin bank.

곽계환 Kae-hwan Kwak , 황해성 Hae-sung Hwang , 김우종 Woo-jong Kim , 장화섭 Hwa-sup Jang , 강신묵 Shin-muk Kang

DOI: JKWST Vol.49(No.2) 27-36, 2007

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This study, the present study wishes to develop a model that estimates shear strength characteristics of steel fiber reinforced concrete using artifical neural network models. Neural network models, developed as mathematical models, are being widely used not only in its original purpose of pattern recognition, but also in application fields by the function's nonlinear loaming and interpolar ability Neural network has a repetitive rotation algorithm that can cyclically and repeatedly estimate system conditions and parameter ideal values, and it can be used in the modeling of the nonlinear system by nonlinear characteristic functions that construct the system.

원종필 Won Jong Pil , 이재영 Lee Jae Young , 박찬기 Park Chan Gi , 박성기 Park Seong Gi

DOI: JKWST Vol.49(No.2) 37-46, 2007

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The service life of agricultural concrete structures is designed in about 30 to 100 years, but actual service lift is estimated in an average 18 years. Therefore, as the service life of the agricultural concrete structures increases, necessity of repair by aging from various environment condition exposure increases. This study was to determinate the optimum mix proportion of latex modified repair mortar and to improve the durability performance of agricultural concrete structures. The physical and mechanical tests of latex modified repair mortar were performed. Tests of flow, compressive strength, flexural strength and bond strength tests were conducted. Test results show that the optimum nex proportion of latex modified repair mortar, when used in 5% latex volume fraction (weight of cement), 1.5% antifoaming agent (weight of latex), 0.2% PVA fiber volume fraction, 1:2 (binder-sand ratio), 10% silica fume replacement ratio (weight of cement), could result in best performance for the repair of agricultural concrete structures.

허성구 Heo Sung Gu , 김재영 Kim Jae Young , 유동선 Yoo Dong Sun , 김기성 Kim Ki Sung , 안재훈 Ahn Jae Hun , 윤정숙 Yoon Jong Suk , 임경재 Lim Kyoung Jae

DOI: JKWST Vol.49(No.2) 49-60, 2007

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The alpine agricultural activities are usually performed at higher and steep areas in nature. Thus, significant amounts of soil erosion are occurring compared with those from other areas. Thus, the soil erosion induced environmental impacts in these areas are getting greater. The Doam watershed is located at alpine areas and it has been well known that the agricultural activities in the watershed are causing accelerated soil erosion and water quality degradations. Many modeling approaches were employed to solve soil erosion and water quality issues. In this study, the Soil and Water Assessment Tool (SWAT) model was utilized to simulate the hydrologic and sediment behaviors in the Doam watershed. In many previous modeling studies, the digital soil map and its corresponding soil properties were used without modification to reflect soil conditioning at many agricultural fields of the Doam watershed. Thus, the soil sample was taken at the agricultural field within the Doam watershed and analyzed for its physical properties. In this study, the digital topsoil properties in the agricultural fields within the Doam watershed were replaced with the soil properties for reconditioned soil analyzed in this study to simulate the impacts of using soil properties for reconditioned soil in hydrologic and sediment modeling at the Doam watershed using the SWAT model. The hydrologic component of the SWAT model was calibrated and validated for measured flow data from 2002 to 2003. The R² value was 0.79 and the EI value was 0.53 for weekly simulated data. The calibrated model parameters were used for hydrologic component validation and the R2 value was 0.86 and the EI value was 0.74 for weekly data. For sediment comparison, the R2 value was 0.67 and the EI value was 0.59. These statistics Improved with the use of soil properties of the reconditioned soil in the field compared with the results obtained without considering soil reconditioning. The simulated sediment amounts with and without con-sidering the soil properties of the reconditioned soil were 284,813 ton and 158,369 ton, respectively. This result indicates that there could be approximately 79% of errors in estimated sediment yield at the Doam and without considering soil properties from the reconditioned soil.

정광욱 Kwang-wook Jung , 윤춘경 Chun G. Yoon , 장재호 Jae-ho Jang , 김형철 Hyung-chul Kim

DOI: JKWST Vol.49(No.2) 61-74, 2007

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A mathematical modeling program called Hydrological Simulation Program-FORTRAN (HSPF) developed by the United States Environmental Protection Agency (EPA) was applied to Hwaseong watershed. It was run under BASINS (Better Assessment Science for Integrating Point and Nonpoint Sources) program, and the model was validated using monitoring data of 2002∼2005. The model efficiency of runoff ranged from good to fair in comparison between simulated and observed data, while it was from very good to poor in the water quality parameters. But its reliability and performance were within the expectation considering complexity of the watershed and pollutant sources. The nonpoint source (NPS) loading for T-N and T-P during the monsoon rainy season (June to September) was about 80% of total NPS loading, and runoff volume was also in a similar range. However, NPS loading for BOD (55∼60%) didn't depend on rainfall because BOD was mostly discharged from point source (more than 70%). And water quality was not necessarily high during the rainy season, and showed a decreasing trend with increasing water flow. BASINS/HSPF was applied to the Hwaseong watershed successfully without difficulty, and it was found that the model could be used conveniently to assess watershed characteristics and to estimate pollutant loading including point and nonpoint sources in watershed scale.

김태규 Kim Tae Kyu

DOI: JKWST Vol.49(No.2) 75-86, 2007

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This process which has a connection of biofilter and sulfur-limestone has been developed to treat organic substances including BOD, COD and SS etc. and treat sulfur-limestone is for denitrification.. The whole process consists of chemical reaction tank, sedimentation tank, trickling filter, denitrification tank is filled with sulfur-limestone mixed media. After setting up practical facilities whose capacity is 60 tons a day, we have observed the removal efficiencies of pollutants through 60 experiments during Summer and Winter seasons. The average concentration of polluted water was BOD for 3.6 mg/L, COD_Mnfor 11.3 mg/L, SS for 2.8 mg/L, T-N for 8.6 mg/L, and T-P for 0.8mg/L, and the rate of treatment efficiencies 96.5%, 84.7%, 96.5%, 79.2%, and 80.8%, respectively was found through the experiments. The average treatment efficiency for BOD and COD_Mn was 85.0% and 55.7%, respectively and the average removal efficiency for NH4+-N was 84.9% in the trickling filter. The removal efficiency in the denitrification tank is as follows; The removal rate of NO₃-N and 0.1~8.3 mg/L outflown. It had observed that this process has implemented highly efficient and advanced treatment without external carbon sources and internal recycle during its process. In conclusion, this process is suitable for a sewerage in a small village due to the merits of low power consumption and easy maintenance.

최연식 Choi C. Yeonsik , 송인홍 Song Inhong , 권순국 Kwun Soon Kuk

DOI: JKWST Vol.49(No.2) 87-97, 2007

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The aim of this study was to compare crop contamination between two irrigation methods using microbial-contaminated water. The effect of relative humidity on microbial survival of the three indicator microorganisms was also investigated. Escherichia coli ATCC 25922, Clostridium perfringens ATCC 3624, and coliphage PRD1 were applied to irrigation water to grow cantaloupe, lettuce, and bell pepper. Half of the sixteen plots were subsurface drip irrigated (SDI) and the other half were furrow irrigated (FI). Two relative humidity levels were controlled at 15-65 % and 55-80 % for the dry and humid condition experiments, respectively. Samples of produce, surface soil, and subsurface soil at a depth of 10 cm were collected over a two-week period following the application of the study microorganisms. Overall, greater contamination of both produce and soil occurred in the FI plots. For the SDI plots, preferential water paths and resulting water appearance on the seed beds seemed to be responsible for produce contamination. Relative humidity levels did not appear to affect microbial survival in soil. PRD 1 showed lower inactivation rates than E. coli in both dry and humid conditions. C. perfringens did not experience significant inactivation over the experimental period, suggesting this microorganism can be an effective indicator of fecal contamination.

오광영 Oh Kwang Young , 김진수 Kim Jin Soo , 조재원 Cho Jae Won

DOI: JKWST Vol.49(No.2) 99-108, 2007

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The purpose of this study was to investigate characteristics of concentrations of pollutants such as TN (Total Nitrogen), TP (Total Phosphorus) and COD (Chemical Oxygen Demand) in outflow from a nonpoint source dominated watershed (6.7 km²). Regular flow measurement and water sampling were taken at five-day intervals during two years (February 2002 to January 2004) in the Ingyeong River, a tributary of the Han River. The mean concentrations of pollutants during rainy days were significantly (p<0.05) higher than those during dry days. For dry days, the flow-weighted mean concentration (0.06 mg/L) of TP during paddy irrigation periods were higher than that (0.02 mg/L) during non-irrigation periods. The seasonal mean concentration of TN was highest in spring likely due to nitrogen fertilization, but those of TP and COD were highest in summer due to particulate phosphorus and sediment-associated organic matter caused by increased discharge. The pollutant concentrations significantly increased with discharge, suggesting that the measures to reduce the increase in the concentrations during storms are needed to control nonpoint source pollution.