Recently, the frequency and intensity of drought have been increasing due to the sudden abnormal climate in Korea. The occurrence of agricultural drought has been steadily increasing from 5 times in the 1980s to 2000s in 20 years, 6 times in the 10 years from 2000 to 2010, and 4 times in the recent period from 2011 to 2015. Therefore, this study analyzed the effect of water shortage caused by drought by improving the function of agricultural reservoir.
The target area analyzed the data such as “Comprehensive Information System for Rural Water” operated by Korea Rural Community Corporation. As a result, we selected the target area as Wanju - gun, Jeollabuk - do in consideration of the rate of water storage compared with the normal 25 years, the completion year of the facility, the area of coverage per reservoir site and the low capacity. As a result of evaluating the improvement effect of agricultural facilities, it was analyzed that the irrigation area increased by about 25.7% when the water level was increased by 1m and the irrigation area increased by about 51.3% when the water level was increased by 2m. The results of the drought impact assessment after improving the function of the agricultural facilities were analyzed that it was effective to improve the function after more than 4m depth.
Assessment of Reference Evapotranspiration Equations for Missing and Estimated Weather Data
Estimating the reference evapotranspiration is an important factor to consider in irrigation system design and agricultural water use. However, there is a limitation in using the FAO Penman-Monteith (FAO P-M) equation, which requires various meteorological data. The purpose of this study is to compare three reference evapotranspiration (ETo) equations in the case of meteorological data missing for 11 study weather stations. Firstly, the FAO P-M equation is used for reference potential evapotranspiration estimation with the actual solar radiation data Rn and the actual vapor pressure ea. Then, in the case of Rn, and ea are missed, the reference evapotranspirations applying FAO P-M, Priestley-Taylor (P-T), Hargreaves (HG) equation were calculated using other meteorological factors. Secondly, MAE, RMSE, R2 were calculated to compare ETo relationship from the ETo equations. From the results, ETo with Hargreaves equation in coastal areas and the Priestley-Taylor equation in the inland areas showed relatively high correlation with FAO P-M when ea data is missed. In the case of Rn data is missed or two weather data, ea, and Rn data are all missed, R2 value in Priestley-Taylor equation was highest in coastal areas, and R2 values in Hargreaves equation were the high values for 7 inland areas. The results of sensitivity analysis showed that net radiation was the most sensitive for P-T and HG equation, and for FAO P-M, the most sensitive factor was net radiation and relative humidity, air temperature and wind speed were follows. Therefore, in considering of the accessibility to the coast, the types of the missing wether data, and the correlation and the magnitude of error, the reference evapotranspiration equations would be selected in sense of different conditions.
CFD Modeling of Pesticide Flow and Drift from an Orchard Sprayer
Effective pesticide applications are needed to assure the quality and economic competitiveness of fruit production and lower the risk of spray drift. Experimental studies have shown that better spray coverage and less driftability require an understanding of the transport of spray droplets within turbulent airflows in the orchard and the interaction between droplet dynamics and tree canopies. This study developed a computational fluid dynamics (CFD) model to predict pesticide flows in the orchard and spray drift discharged from an air-assisted orchard sprayer. The model represented the transport of spray droplets as well as droplets captured by tree canopies, which were modeled as a conical porous model and branched tree model. Validation of the CFD model was accomplished by comparing the CFD results with field measurements. Spray depositions inside tree canopies and at off-target locations were in good agreement with the measurements. The resulting data presented that 38.6%∼42.3% of the sprayed droplets were delivered to the tree canopies while 13.6%∼20.1% were drifted out of the orchard, part of them reached farther than 200 m from the orchard. The study demonstrates that CFD model can be used to evaluate spray application performance and spray drift potential.
A Comparison of the Impact of Regional Anthropogenic Climatic Change in Urban and Rural Areas in South Korea (1955-2016)
윤동현 Yoon Dong-hyun , 남원호 Nam Won-ho , 홍은미 Hong Eun-mi , 김태곤 Kim Taegon , 허창회 Ho Chang-hoi , Michael J. Hayes
Local climate characteristics for both urban and rural areas can be attributed to multiple factors. Two factors affecting these characteristics include: 1) greenhouse gases related to global warming, and 2) urban heat island (UHI) effects caused by changes in surface land use and energy balances related to rapid urbanization. Because of the unique hydrological and climatological characteristics of cities compared with rural and forested areas, distinguishing the impacts of global warming urbanization is important. In this study, we analyzed anthropogenic climatic changes caused by rapid urbanization. Weather elements (maximum temperature, minimum temperature, and precipitation) over the last 60 years (1955-2016) are compared in urban areas (Seoul, Incheon, Pohang, Daegu, Jeonju, Ulsan, Gwangju, Busan) and rural/forested areas (Gangneung, Chupungnyeong, Mokpo, and Yeosu). Temperature differences between these areas reveal the effects of urbanization and global warming. The findings of this study can be used to analyze and forecast the impacts of climate change and urbanization in other urban and non-urban areas.
Analysis of Environmental Impacts and Alternative Scenarios of Transportation Stages on Food Miles for Major Imported Crops
김찬우 Kim Chanwoo , 김솔희 Kim Solhee , 정찬훈 Jung Chanhoon , 서교 Suh Kyo
Transportation and storage technologies, which are key drivers for trade, has increased global trade of agricultural products about 165% from 1995 to 2015. Korea imports 76.2% of grain from major food exporters such as USA, Australia, Brazil, and China. The expected long shipping distances from these countries can seriously cause environmental impacts on various environmental categories such as climate change, particulate matter, and acidification. The goal of this study is to assess the environmental implications focused on greenhouse gases (GHGs) and particulate matters (PMs) emissions of imported grains (wheat, corn, and bean) using food miles analysis and life cycle assessment (LCA). The environmental impacts of imported crops are estimated by transportation modes using the national LCI database provided by Korea Environmental Industry & Technology Institute (KEITI). The results of this study are as follows; (1) Imported wheat comes from USA (29%), AUS (27%), and URK (20%), corn is imported from USA (34%), BRA (29%), and URK (16%), and bean comes from BRA (57%), USA (40%), and CHN (2%); (2) the food miles of imported crops (wheat, corn, and bean) are 3.62E+10, 1.30E+11, and 2.20E+10 ton·km, respectively; (3) the potential GHGs and PMs of wheat, corn, and bean are 5.02E+08, 1.67E+09, and 2.84E+08 kg CO2e and 5.89E+05, 1.83E+06, 3.07E+05 kg PM10e, respectively. The outputs of this study could provide environmental impacts and carrying distances of imported agricultural products for preparing a plan to reduce environmental impacts.
Effect of Probability Distribution of Coefficient of Consolidation on Probabilistic Analysis of Consolidation in Heterogeneous Soil
In this study, a simple probabilistic approach using equivalent coefficient of consolidation (ce) was proposed to consider the spatial variability of coefficient of vertical consolidation (cv), and the effect of the probability distribution of coefficient of consolidation on degree of consolidation in heterogeneous soil was investigated. The statistical characteristics of consolidation coefficient were estimated from 1,226 field data, and four probability distributions (Normal, Log-normal, Gamma, and Weibull) were applied to consider the effect of probability distribution. The random fields of coefficient of consolidation were generated based on Karhunen-Loeve expansion. Then, the equivalent coefficient of consolidation was calculated from the random field and used as the input value of consolidation analysis. As a result, the probabilistic analysis can be performed effectively by separating random field and numerical analysis, and probabilistic analysis was performed using a Latin hypercube Monte Carlo simulation. The results showed that the statistical properties of ce were changed by the probability distribution and spatial variability of cv, and the probability distribution of cv has considerable effects on the probabilistic results. There was a large difference of failure probability depend on the probability distribution when the autocorrelation distance was small (i.e., highly heterogeneous soil). Therefore, the selection of a suitable probability distribution of cv is very important for reliable probabilistic analysis of consolidation.
Evaluating Proper CO2 Concentrations in CA Storage of Fuji Apple using CFD Analysis
이상익 Lee Sang-ik , 홍세운 Hong Se-woon , 최원 Choi Won , 김락우 Kim Rack-woo , 이인복 Lee In-bok
CO2 concentration has a significant effect on quality of cold-stored apples. High indoor CO2 concentrations above 10,000 ppm cause the browning of apples and result in economic loss for farmers. The purpose of this study is to evaluate CO2 concentrations and their distribution in a controlled atmosphere (CA) storage and provide better structural designs to improve the CO2 environment using computational fluid dynamics (CFD) simulations. The CFD model was developed for a real CA storage for apples and applied to investigate the effect of changing the inlet and outlet locations and the aspect ratio of the floor of the CA storage on the spatial distributions of CO2 concentration and the browning of the apples. The lowest CO2 concentrations in existing CA storage with a high aspect ratio of the floor were achieved from the combination of the inlet located at the top of the right side and the outlet located at the bottom of the left side. In modified CA storage with a low aspect ratio, the combination of the inlet and outlet located at top and bottom of left side respectively achieved the lowest CO2 concentrations. The proposed case enhanced the storage performance by reducing total browned apples by 3.6% in storage duration of 210 days. This study is expected to reduce the browning damages of apples in CA storage, and thus greatly prevent economic losses.
A Study to Apply the Logic Model for Evaluating Outcomes of Revitalization Projects of Rural Centers: Focusing on Regional Capacity Strengthening in Yeongwol-gun
김기성 Kim Kisung , 정미경 Jeong Meekyung , 나권희 Na Kweonhee
A Study to Apply the Logic Model for Evaluating Outcomes of Revitalization Projects of Rural Centers: Focusing on Regional Capacity Strengthening in Yeongwol-gun
김기성 Kim Kisung , 정미경 Jeong Meekyung , 나권희 Na Kweonhee
This study aims to apply the logic model in order to evaluate outcomes of revitalization projects of rural centers as a part of the regional capacity strengthening in Yeongwol-gun. According to the study results, first of all, it was unclear to answer for questions what, how and why to lead the project, when examining logical associations among program inputs, activities, outputs and outcomes. As an alternative method, the logic model has been applied, and this in turn led to clarify the goals, inputs, contents, outputs, outcomes as well as overall outcome goals and purpose of the current projects. Second of all, the initial, intermediate and long term outcome goals of the current project were indistinctly specified, and moreover, their evaluation methods were also unclear. By applying the logic model to the current regional capacity strengthening project, it was able to figure the distinction between program outputs and outcomes, and specify initial, intermediate and long term target goals as well as their evaluation tools. It is therefore to conclude that the logic model has a possibility to apply to a project evaluation, especially in the sense that this method considers efficiency, effectiveness and accountability of each project.
Understanding the composition of the dam inflow can improve the efficiency of dam operation considering the seasonal characteristics. Hydrograph analysis is one of the methods to identify the characteristics of dam inflow. In addition, baseflow separation on the dam inflow can be affected by anthropogenic influences depending on dam locations. In this regard, the objectives of this study are 1) to analyze yearly and monthly baseflow contribution to the dam inflow and 2) to compare the baseflow contribution to the inflow in dams located upstream and downstream of the watershed. The result shows that the estimated baseflow index was smaller in the upstream dams compared to the downstream dams. Discharge from the upstream water infrastructure including dams and reservoirs can be a part of inflow into the downstream water infrastructure. Based on this scenario, the discharge regulated from the upstream dam could lead to overestimation of baseflow contribution to inflow into the downstream dam. We expect that the results from this study elucidate the role and function of dams and hence, contribute to the efficient operation of dams located in the upstream and the downstream of the watershed.
The Analysis of Nitrogen Supply Amount in Paddy Fields by Rainfall During Cropping and Non-Cropping Period
최동호 Choi Dongho , 최순군 Choi Soon-kun , 허승오 Hur Seung-oh , 홍성창 Hong Seung-chang , 김민경 Kim Min-kyeong
In this study, we conducted to analyze and quantify the amount of nitrogen supply into the rice paddies from the rainfall during cropping and non-crop periods. Rainfall monitoring conducted 85 times from June 2015 to December 2017. Nitrogen supply of cropping season ranged from 5.37 to 7.70 kg/ha, while non-cropping season were supplied from 3.97 to 4.42 kg/ha. The supply of T-N in the crop period was more than 60% of the total supply. And as a result of analyzing the correlation between the characteristics of rainfall and the supply amount, nitrogen concentrations in rainfall were decreased with increasing rainfall, but the supply amount was increased. Therefore, efforts should be made to increase the rainfall utilization and to increase the nitrogen supply of crops by increasing rainfall storage through drainage management.
Effects of the Brackish Water Desalination System on Soil Environment and Growth in Squash Greenhouse Cultivation Area
김수진 Kim Soo-jin , 배승종 Bae Seung-jong , 정한석 Jeong Han-suk , 김학관 Kim Hak-kwan , 박승우 Park Seung-woo
The objectives of the research were 1) to develop the low-cost and high efficient desalination system to treat brackish water having high salt contents for irrigation at greenhouses near coast, and 2) to monitor and assess the effects of the brackish water desalination system on soil environment and growth in squash greenhouse cultivation area. The monitoring site was one of the squash greenhouse cultivation farm at Choengam-ri, Jinsang-myun, Gwangyang-si, Jeonnam-Do Monitoring results for groundwater irrigation water quality, and salinity showed a remarkable difference between control and treatment group. The salinity of soil at treatment group was less than at control group. While, the system made possible to increase the squash quantity from 4.7 ea to 6.3 ea at each and the average weight of the harvested squash was increased from 277.2 g to 295.1 g. The applied brackish water desalination system may be appled to reclaim sea or brackish irrigated area as alternative water resources, although long-term monitoring is needed to get more representative results at different level of salinity.
Experimental Study on Evaluation of Abrasion Resistance of Concrete Irrigation Facilities
The purpose of this paper is to propose an experimental method to evaluate the resistance of abrasion about 24 MPa, 27 MPa, and 30 MPa compressive strength. These strength are used in the design and construction of concrete hydraulic structures in Korea. The mixing ratios of the ready mixed concrete strengths were investigated countrywide and set the representative mixture proportion ratios of the nine mixed types of OPC, FA and BFS. After making and curing the test specimens, the underwater abrasion test was performed. ASTM C 1138 International Standard was used to fabricate the test equipment, and the surface abrasion resistance of the specimen was tested using the test equipment. In the case of OPC, the 30% abrasion resistance improvement effect was observed at 72 hours as the water-binder ratio decreased. That was reason the coated cement bond strength of the specimen was strong. In the case of BFS and FA, it was improved by 9.9% and 3.8%, respectively, at 72 hours as the water-binder ratio decreased. It was due to the characteristics of the latent hydraulic and pozzolanic reactions. Generally, the relative abrasion resistance of concrete can be evaluated at 24 hours. However, in case of low strength (under 24 MPa), the surface mortar layer wears much faster at the first 12 hours, so it can be considered to evaluate the relative abrasion loss rate at this point.
Modeling Sedimentation Process in Ipjang Reservoir using SWAT and EFDC
신샛별 Shin Sat Byeol , 황순호 Hwang Soon-ho , 허용구 Her Younggu , 송정헌 Song Jung Hun , 김학관 Kim Hak Kwan , 강문성 Kang Moon Seong
Reservoir sedimentation is a major environmental issue, and various sediment load controls and plans have been proposed to secure clean and safe water resources. The objectives of this study were to estimate soil loss in the upper basins and predict sediment deposition in Ipjang reservoir using hydrologic and hydraulic model. To do so, SWAT (Soil and Water Assessment Tool) and EFDC (Environmental Fluid Dynamics Code) was used to estimate soil loss in two upper basins and to predict spatial distribution and amount of sediment deposition in the Ipjang reservoir, respectively. The hydrologic modeling results showed that annual average soil loss from the upper basins was 500 ton. The hydraulic modeling results demonstrated that sediment particles transported to the reservoir were mostly trapped in the vicinity of the reservoir inlet and then moved toward the bank over time. If long-term water quality monitoring and sediment survey are performed, this study can be used as a tool for predicting the dredging amount, dredging location and proper dredging cycle in the reservoir. The study findings are expected to be used as a basis to establish management solutions for sediment reduction.
