임성훈 Eam Sung Hoon , 허건 Heo Gun

DOI: JKWST Vol.56(No.6) 1-9, 2014

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In this study the pore water pressures were measured in sea dike constructed with the sand dredged in the sea, and they were analyzed with the hydraulic head loss rate to estimate quantitatively the state of blocking seepage in the sea dike embankment. Blocking state was expressed as the number between 0 and 1. the number of 1 means the state of perfectly blocking seepage and the number of 0 means the state of sea water being passing free. The deeper the installed position was the lower the hydraulic head loss rate was and the longer the seepage path length was the higher the hydraulic head loss rate was. The estimated R-squareds were close to 1, which means that the embankment was steady state without movement of soil particles.

김홍태 Kim Hong Tae , 신동석 Shin Dong Seok , 김용석 Kim Yong Seok

DOI: JKWST Vol.56(No.6) 11-18, 2014

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Vulnerable areas by non-point source pollution and prioritizing control areas were researched using hydrological and geomorphological data, non-point source loads, and water quality data. Using overlay analysis, vulnerable areas were graded with various scenarios. Vulnerable areas were selected near the metro city with impermeable landuse because non-point source loads and water quality data had influence on overlay analysis to rank vulnerable area. Analysis scenarios and weighted values can be changed under regional characteristics and given conditions.

송정헌 Song Jung Hun , 정한석 Jeong Han Seok , 박지훈 Park Ji Hoon , 송인홍 Song In Hong , 강문성 Kang Moon Seong , 박승우 Park Seung Woo

DOI: JKWST Vol.56(No.6) 19-29, 2014

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The objectives of this study were to monitor and analyse water quality and soil property in paddy fields where untreated wastewater is irrigated. Three paddy fields where streamflow mixed with untreated wastewater has been irrigated (untreated wastewater district, UWD) were selected for monitoring, and five paddy fields in Yongin area (Yongin district, YID) where water from Idong agricultural reservoir (well-managed) has been irrigated were selected for comparative evaluation. Electronic conductivity (EC), suspended solids (SS), total nitrogen (T-N), total phosphorous (T-P), NO₃-N, Ca²⁺, Mg²⁺, Na⁺, total coliform (TC), fecal coliform (FC), and E. coli of the irrigation water in the UWD were significantly higher than those in the YID. Relatively high concentrations of EC, T-N, T-P, TC, FC, E. coli, copper (Cu), lead (Pb), zinc (Zn), and aluminium (Al) were shown in the irrigation water of the UWD especially during May to June. In general, the paddy soil in the UWD contained more Pb, Zn, and Cu than in the YID although the soil heavy metal contents in the UWD still meet the Korean soil contamination warning standards. No temporal trends in the heavy metal concentrations were found in paddy soils of the UWD. This study showed that the use of untreated wastewater to paddy fields has the possibility of negative impacts on water quality and soil, although long-term monitoring is needed to fully evaluate its effects.

권경석 Kwon Kyeong Seok , 조예슬 Jo Ye Seul , 이인복 Lee In Bok , 하태환 Ha Tae Hwan , 홍세운 Hong Se Woon

DOI: JKWST Vol.56(No.6) 31-43, 2014

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Confined and mechanically ventilated broiler house has been recently come into wide use to increase productivity and control rearing conditions. However, high dust concentration inside facility can threaten respiratory welfare of farmers and broilers. In Korea, there is no regulation in terms of air quality control inside agricultural facilities and sufficient data is not available. To cope with these, periodic monitoring of inhalable and respirable dust concentration were conducted according to season, broiler’s activity and specific events such as shipment work for broilers in mechanically ventilated broiler house. Chamber experiment was also designed to analyze mechanism of dust generation from ground beds according to water contents and surrounding wind environment. Results showed that significant increase of inhalable (p=0.002) and respirable (p=0.03) dust were observed when activity of broilers was high according to entrance of the workers. Even shipment work for matured broilers, high level of dust were observed; inhalable dust was exceeded the threshold limit over maximum 303 % and respirable dust was over maximum 1,550 %, implying that acute respiratory symptoms could be manifested for the workers. From the chamber experiment, critical water contents for interrupting of dust generation were measured; about 45 % for inhalable dust and about 50 % for respirable dust. These results can be a trigger for designing plan of dust control however it still needs consideration of various environmental conditions, hygiene problems, etc.

정한석 Jeong Han Seok , 성충현 Seong Choung Hyun , 박승우 Park Seung Woo

DOI: JKWST Vol.56(No.6) 45-53, 2014

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This study presents a system dynamics modeling approach to simulate daily streamflow in a watershed including wastewater treatment plant which contributes to irrigation water supply. The conceptual system dynamics model considering the complex and dynamic hydrological processes in the watershed was developed. The model was calibrated and validated each for two years based on observed flow data. Model performances in terms of E_NS, RSR, PBIAS, and R² were 0.64, 0.60, -3.6 %, and 0.64 for calibration period, and 0.66, 0.58, -2.6 %, and 0.66 for validation period, respectively, showing an applicability on generating the daily streamflow. System dynamics modeling approach could help better understand the hydrological behavior of the watershed being reused wastewater for agriculture, by providing graphical dynamics of the hydrological processes as well as conventional rainfall-runoff model results.

강구 Kang Ku , 왕용 Wang Long , 홍성구 Hong Seong Gu

DOI: JKWST Vol.56(No.6) 55-62, 2014

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Torrefaction is considered as a promising pre-treatment for thermochemical utilization of biomass. Torrefaction temperature and time are the critical operation parameters. In this study, investigated were the effects of reaction temperature and time on product composition of torrefaction. scanning electron microscope (SEM) images and thermo gravimetric analyzer (TGA) results were also compared for the effects of the operating parameters. SEM images showed that the pores were observed at the temperature of 250 ℃ for 30 minutes. Rapid decreases in weight were observed the temperature between 200 and 400 ℃. Higher heating value of the torrefied biomass was over 5,000 kcal/kg at the temperature of 250 ℃ for 45 minutes. Energy density, which is defined as the ratio of the energy yield over the mass yield was 1.36 at the temperature of 250 ℃ for 45 minutes. The energy density was higher up to 1.6 at the temperature of 280 ℃, which indicates greater loss in mass. The major components of the gas produced in the torrefaction were CO₂ and CO, with traces of methane. The total amount of gas was 31.54 l/kg and the calorific value of the gas was 1,164.4 Kcal/Nm³ at the temperature of 250 ℃ for 30 minute reaction time. Based on the results of this study, the temperature of effective torrefaction is about 250 ℃ for 30 to 45 minutes of reaction time. Considering the heating value, it is desirable to utilize the gas for efficient process of torrefaction.

이달원 Lee Dal Won , 노재진 Noh Jae Jin

DOI: JKWST Vol.56(No.6) 63-73, 2014

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In this study, the large scale test was performed to investigate the behavior of failure on the embankment and spillway transitional zone by overtopping. The pore water pressure, earth pressure, settlement and failure behaviors according to several reinforcing method were compared and analyzed. The pore water pressure showed a small change in the spillway transition zone and core, indicating that the riprap and geotextile efficiently reinforced the embankment, but non-reinforcement showed a largely change in pore water pressure. The earth pressure by riprap and geotextile at upstream slope and bottom core increased rapidly with the infiltration of the pore water by overtopping. And the earth pressure at crest showed a smally change due to effect of the inclined core. A settlement by riprap showed a small change and the geotextile decreased a rapidly due to failure of crest. The width of failure by riprap at intermediate stage (50 min) showed a largely due to sliding of crest. But, the width and depth of the seepage erosion after the intermediate overtopping period (100 min) were very small due to the effect of riprap than geotextile and non-reinforcement which delayed failure. It has the effect that protect reservoir embankment from erosion in the central part. The pore water pressure at the spillway transition zone due to overtopping increased a rapidly in the case of non-reinforcement, but the reinforced methods by geotextile and riprap showed a smally change. Therefore, the reinforced method by riprap and geotextile was a very effective method to protect permanently and the emergency an embankment due to overtopping, respectively.

이충원 Lee Chung-won , 유지훈 Yoo Ji-hoon , 민연식 Min Yeon-sik , 장동수 Chang Dong-su , 임현택 Lim Hyun-taek , 문용배 Moon Yong-bae , 김승태 Kim Seung-tai , 김용성 Kim Yong-seong

DOI: JKWST Vol.56(No.6) 75-84, 2014

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This study aims to develop the program for design of a reinforced earth retaining wall. For this purpose, the external stability such as overturning, sliding and bearing capacity and the internal stability such as pull-out failure and tensile rupture of the reinforced earth retaining wall with the reinforcement spacing and the backfill inclination were examined. In addition, the calculated results from the developed program were verified by comparing with the simulated results based on the three-dimensional finite element analysis. It is expected that this program contributes to effective design of the reinforced earth retaining wall.

박찬기 Park Chan Gi , 김춘수 Kim Chun Soo , 김황희 Kim Hwang Hee , 유성열 Yoo Sung-yeol , 전지홍 Jeon Ji Hong

DOI: JKWST Vol.56(No.6) 85-91, 2014

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In this study, the water quality purification of new medias which were NPS media, hyugato, mineral stone, charcoal for applying soil media of Integrated Management Practices (IMPs) of Low Impact Development (LID) were evaluated. The influent concentrations of COD, T-N, and T-P were 117.8 mg/L, 17.1 mg/L, and 2.062 mg/L, respectively. The infiltration capacities of NPS media, hyugoto, mineral stone, charcoal, and gravel were 7.1×10 m/s, 7.3×10^-5 m/s, 7.9×10^-5 m/s, 6.0×10^-5 m/s, respectively. All media meet criteria of infiltration capacity as surface soil layer at IMPs which is over 1.0×10^-5 m/s. Maximum removal rates of COD, T-N, and T-P occurred at Charcoal with 98 % of COD removal rate, NPS with 78 % of T-N removal rate, and hyugato with 75 % fo T-P removal rate, respectively. For more high removal efficiency of all water quality item, the mixed media which is 4.5(NPS media): 1(charcoal) : 4.5 (hyugato) as volume ratio was evaluated. The infiltration capacity of mixed media was 7.9×10^-5 m/s and met the criteria of infiltration as surface soil layer. The water quality removal efficiencies of mixed media were very high with showing 70 % for COD, 85 % for T-N, and 71 % for T-P. The mixed media could purify the water quality of surface runoff and was recommended to used at the LID site of ground water quality problem.

김태곤 Kim Taegon , 이정재 Lee Jeongjae , 남원호 Nam Won-ho , 서교 Suh Kyo

DOI: JKWST Vol.56(No.6) 93-102, 2014

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Generally data loading is a laborous job to develop models. Meteorological data is basic input data for hydrological models, it is provided through websites of Korea Meteorological Administration (KMA). The website of KMA provides daily meteorological observation data with tabular format classified by years, items, stations. It is cumbersome to manipulate tabular format for model inputs such as time series and multi-item or multi-station data. The provider oriented services which broadcast restricted formed information have caused inconvenient processes. Tim O'Reilly introduces “Web 2.0” which focuses on providing a service based on data. The top ranked IT companies such as google, yahoo, daum, and naver provide customer oriented services with Open API (Application Programming Interface). A RESTful web service, typical implementation for Open API, consists URI request and HTTP response which are simple and light weight protocol than SOAP (Simple Object Access Protocol). The aim of this study is to develop a web-based service that helps loading data for human use instead of machine use. In this study, the developed RESTful web service provides Open API for manipulating meteorological data. The proposed Open API can easily access from spreadsheet programs, web browsers, and various programming environments.

정인균 Jung In Kyun , 박종윤 Park Jong Yoon , 김성준 Kim Seong Joon , 장철희 Jang Cheol Hee

DOI: JKWST Vol.56(No.6) 103-111, 2014

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This study was to develop the flood analysis module (FAM) for implementation of a web-based real-time agricultural flood management system. The FAM was developed to apply for an individual watershed, including agricultural reservoir. This module calculates the flood inflow hydrograph to the reservoir using effective rainfall by NRCS-CN method and unit hydrograph calculated by Clark, SCS, and Nakayasu synthetic unit hydrograph methods, and then perform the reservoir routing by modified Puls method. It was programmed to consider the automatic reservoir operation method (AutoROM) based on flood control water level of reservoir. For a 15.7 km² Gyeryong watershed including 472×10⁴ m³ agricultural reservoir, rainfall loss, rainfall excess, peak inflow, total inflow, maximum discharge, and maximum water level for each duration time were compared between the FAM and HEC-HMS (applied SCS and Clark unit hydrograph methods). The FAM results showed entirely consistent for all components with simulated results by HEC-HMS. It means that the applied methods to the FAM were implemented properly.

이충원 Lee Chung Won , 김정면 Kim Jung Myeon , 문용배 Moon Yong Bae , 김용성 Kim Yong Seong

DOI: JKWST Vol.56(No.6) 113-119, 2014

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This study aims to evaluate the behavior of poorly-compacted raised reservoir levee with water level raising by using centrifugal model test. From the test results, it seems that the hydraulic fracturing at the core of the raised reservoir levee with low degree of compaction possibly occurs due to the drastical increase of pore water pressure by water level raising. Additionally, the continuous infiltration may induce crack and/or sinkhole on the surface of the poorly-compacted raised reservoir levee owing to the increase of the subsidences at the crown and the front side of that. Therefore, reasonable construction management for the compaction of the raised reservoir levee is needed.

송창섭 Song Chang Seob , 임성윤 Lim Seong Yoon

DOI: JKWST Vol.56(No.6) 121-128, 2014

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Development of the economic methods and the design of the standard sections needs the more project fund and land than ever leads to the objection of enlarging canal arrangement to need economic construction method development and standard design for supporting it. The objective of this study was to evaluate the performance of selected sediment reduction methods to reduce sediment discharges from drain and irrigation of different land types (Mountain, Flatten, Reclaimed land). This study was carried out to analysis for the soil loss and sediment of drain and irrigation by comparing RUSLE method and amount of sediment from amount of dredging data of Korea Rural Corporation. The results of study were analyzed and summarized as follow. Size of soil sediment from the upper region of drain and irrigation of mountains bigger than lower region. But in case of flatten and reclaimed land, size of soil sediment from the upper and lower region of drain and irrigation did not classified. In case of comparison drain and irrigation without classifying of land type, size of soil sediment from irrigation is bigger than drain.

성충현 Seong Choung Hyun

DOI: JKWST Vol.56(No.6) 129-137, 2014

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This research presents an streamflow modeling approach in a data-scarce estuary reservoir watershed which has been suffered from high salinity irrigation water problem after completion of land reclamation project in South Korea. Since limited hydrology data was available on the Iwon estuary reservoir watershed, water balance relation of the reservoir was used to estimate runoff from upstream of the reservoir. Water balance components in the reservoir consists precipitation, inflow from upstream, discharge through sluice, and evaporation. Estimated daily inflow data, which is stream discharge from upstream, shows a good consistency with the observed water level data in the reservoir in terms of EI (0.93) and R² (0.94), and were used as observed flow data for the streamflow modeling. HSPF (Hydrological Simulation Program - Fortran) was used to simulate hydrologic response of upstream of the reservoir. The model was calibrated and validated for the periods of 2006 to 2007 and 2008 to 2009, respectively, showing that values of EI and R² were 0.89 and 0.91 for calibration period, 0.71 and 0.84 for validation period.

성충현 Seong Choung Hyun

DOI: JKWST Vol.56(No.6) 139-147, 2014

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Forecasting salinity in an estuary reservoir is essential to promise irrigation water for the reclaimed land. The objective of the research was to assess salinity balance and its temporal and spatial variations in the Iwon estuary reservoir which has been issued by its high contents of salinity in spite of desalination process for four years. Seepage flows through the see dikes which could be one of possible reason of high salinity level of the reservoir was calculated based on the salinity balance in the reservoir, and used as input data for salinity modeling. A three-dimensional hydrodynamic model, Environmental Fluid Dynamics Code (EFDC), was used to simulate salinity level in the reservoir. The model was calibrated and validated based on weekly or biweekly observed salinity data from 2006 to 2010 in four different locations in the reservoir. The values of R², RMSE and RMAE between simulated and observed salinity were calculated as 0.70, 2.16 dS/m, and 1.72 dS/m for calibration period, and 0.89, 1.15 dS/m, and 0.89 dS/m for validation period, respectively, showing that simulation results was generally consistent with the observation data.

문종필 Moon Jong Pil , 강금춘 Kang Geum Choon , 권진경 Kwon Jin Kyung , 이수장 Lee Su Jang , 이종남 Lee Jong Nam

DOI: JKWST Vol.56(No.6) 149-158, 2014

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The effects of spot cooling on growing ever-bearing strawberry in hydroponic cultivation during summer by spot cooling system was estimated in plastic greenhouse located in Pyeongchang. The temperature of cooling water was controlled by heat pump and maintained at the range of 15~20 ℃. Cooling pipes were installed in root zone and very close to crown. Spot cooling effect was estimated by applying system in three cases which were cooling root zone, crown plus root zone, and crown only. White low density polyethylene pipe in nominal diameter of 16 mm was installed on crown spot, and Stainless steel flexible pipe in nominal diameter of 15A was installed in root zone. Crown and root zone cooling water circulation was continuously performed at flowrates of 300 ~ 600 L/hr all day long. Strawberry yields by test beds were surveyed from Aug. 1 to Sep. 30. The accumulated yield growth rate compared with a control bed of crown cooling bed was 25 % and that of crown plus root zone cooling bed was 25 % and that of root zone cooling bed was 20 %. The temperatures of root spot in root zone cooling was maintained at 18.0 ~ 23.0 ℃ and that of crown spot in crown cooling was maintained at 19~24 ℃. Also, the temperatures of root spot in crown plus root zone cooling bed was maintained at 17.0 ~ 22.0 ℃ and that of crown spot was maintained at 19~25 ℃.

임성훈 Eam Sung Hoon , 허건 Heo Gun

DOI: JKWST Vol.56(No.6) 159-167, 2014

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In this study the process of normalizing hydraulic head loss rate was developed for the purpose of estimation of seepage blocking state at each seepage segment in sea dike embankment. Pore water pressure sensors were installed with some interval along seepage path, then the hydraulic head loss rate at each segment between pore water pressure sensors was calculated, and then the calculated hydraulic head loss rate was normalized based on seepage path length. The comparison of normalized hydraulic head loss rates showed that the cross section of sea dike embankment was homogeneous approximately and the width of cross section was long enough to blocking tide water.

김기욱 Ki-wook Kim , 윤성욱 Sung-wook Yun , 정유진 Eu-jin Chung , 정영륜 Young-ryun Chung , 유찬 Chan Yu

DOI: JKWST Vol.56(No.6) 169-176, 2014

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To evaluate bio-cementation of microbial on sands, laboratory test was conducted using acrylic cubic molding boxes (5 cm x 5 cm x 5 cm). It was incubated the microbial, called Bacillus Pasteurii, according to Park et al (2011, 2012). and applied 50ml each specimen. Two type of sand samples used were Jumoonjin sand and common sand (well graded). These sands were molded in acrylic boxes with the relative density of 30 % and 60 % respectively. Microbial were poured onto the samples molded in acrylic boxes and cured at the room temperature and humidity. After 7, 14 and 21days, it was measured the compressive strength, pH, EC, and density and it were observed SEM and XRD to verify the effect of bio-cementation. It was found that bio-cementation was increased a strength of sands and it was appeared that strengths were related to the type of sand and relative density. Therefore it was confirmed the solidification of sands using the bio-cementation by microbial activation and the usefullness of acrylic molding boxes when tests were conducted on the soil of sands.