국내 논필지 모니터링 자료를 이용한 APEX-paddy 모델 적용성 평가

APEX 모형은 다양한 영농 활동의 토양과 물환경에 대한 영향을 필지 및 유역 규모로 평가하기 위해 개발된 모형이다. 최근 APEX의 주요기작을 바탕으로 논에서의 수도작 운영에 따른 물수지, 양분 유출에 대한 모의가 가능하도록 한 APEX-Paddy가 고안된 바 있다. 본연구에서는 익산 지역의 논 시험포 모니터링 자료를 이용하여 APEX-Paddy 모형의 적용성을 평가하고자 하였다. 2013년과 2014년의 논유출량과 부하량 자료를 수집하고 자동보정 툴 APEX-CUTE 4.1과 추가적 수동보정을 통해 모형의 모의성능을 검토하고 한계점을고찰하였다. 연구결과, 논의 물수지와 질소 배출부하량은 대체로 합리적인 수준의 모의성능을 보이는 한편 유사량과 인 배출부하량 모의에있어 논의 담수상태 유사배출 기작에 대한 고려가 미흡하여 모의성능에 한계가 있는 것으로 분석되었으며 원인에 대해 고찰하였다. 더불어자동보정 툴의 적용에 있어 매개변수 민감도를 바탕으로 한 수동보정 결과보다 정확도가 다소 떨어지는 경향을 보여 그 활용에 유의가필요한 것으로 판단되었다. The APEX model has been developed for assessing agricultural management efforts and their effects on soil and water at the field scale as well asmore complex multi-subarea landscapes, whole farms, and watersheds. Recently, a key component of APEX application, named APEX-Paddy, hasbeen modified for simulating water quality by considering paddy rice management practices. In this study, the performance of the APEX-Paddy modelwas evaluated using field data at Iksan experimental paddy sites in Korea. The discharge and pollutant load data during 2013 and 2014 were usedto both manually and automatically calibrate the model. The APEX auto-calibration tool (APEX-CUTE 4.1) was used for model calibration andsensitivity analysis. Results indicate that APEX-Paddy reasonably performs in predicting runoff discharge rate and nitrogen yield. However, sedimentand phosphorus yield is not correctly predicted due to the limitation of model schemes. With APEX-Paddy, the performance in reproducing thedischarge and nitrogen yield is found to be a satisfactory level after manual calibration. The manually calibrated model performed better than theautomatically calibrated model in nearly all comparisons. For runoff, manual calibration reduced PBIAS while R2 and NSE values of the automaticallycalibrated model were the same as the manual calibration. For T-N, NSE and PBIAS were reduced when using manual calibration, whereas R2 valuewas the same as manual calibration. The limitation of the APEX-Paddy model for predicting sediment, as well as the phosphorous yield, was discussedin this study.N

Subsurface drip irrigation with wastewater and the effects of environmental factors on virus survival in soil

Wastewater reuse for agricultural purposes has been considered as an alternative strategy for water conservation. This study compared subsurface drip irrigation with furrow irrigation in terms of water use efficiency and crop contamination when microbial-contaminated water was used for irrigation. The effects of temperature and moisture on virus survival in soil were assessed quantitatively. Escherichia coli ATCC 25922, Clostridium perfringens, and coliphage PRD-1 served as the study microorganisms. Subsurface drip irrigation used water more efficiently than furrow irrigation due to lower water requirement for similar crop yields. Subsurface drip irrigation performed better for the deep-rooted crops, cantaloupe and bell pepper, compared to the shallow-rooted crop, lettuce. The more water was held by soil and was available for the crop uptake with the deeper root crops than shallow root crops. Overall, significantly greater microbial contamination of produce and soil surface occurred in furrow irrigated plots as compared to subsurface drip irrigated plots. Direct movement of irrigated water to the soil surface appeared to cause crop contamination in subsurface drip irrigation plots. Coliphage PRD-1 demonstrated greater crop contamination and longer survival in the environment compared to E. coli. The smaller size of PRD-1 than that of E. coli seemed to facilitate its movement through soil matrices and increased the chance to contaminate crop produce. The inactivation rate of PRD-1 increased as temperature increased. A soil moisture decrease from 20.9 to 8.9% appeared to be inversely related to the inactivation rate. Further decrease of the soil moisture content to 5.1% increased the inactivation rate. An optimum or a threshold soil moisture level for PRD-1 survival may exist. Evaporation increased the inactivation rate of PRD-1 substantially in higher temperatures but minimally in lower temperatures. A developed model predicted the inactivation rates of PRD-1 in field conditions with an average error of 11.0%. Subsurface drip irrigation with a proper management can be a sustainable strategy to conserve irrigation water as well as to reduce crop contamination when wastewater is used for crop production. PRD-1 survived better at low temperatures and dry soil moisture conditions

Assessment of Agricultural Drought Vulnerability with Focus on Upland Fields and Identification of Primary Management Areas

Robust water management systems are crucial for sustainable water use, particularly considering rapidly changing, ever-improving water supply system technologies. However, the establishment of specific management standards in upland fields is challenging, as several types of crops are cultivated in upland fields. Hence, the timing and required amount of water vary greatly, further rendering drought response challenging. In this study, we evaluated the agricultural drought vulnerability of South Korean upland fields, considering the lack of water resources, to establish preliminary drought damage prevention measures. The Technique for Order of Preference method was used for the drought vulnerability assessment, and the assessment indicators used were annual rainfall, number of dry days, upland field area, available soil water capacity, and groundwater usage. The 20 areas of highest vulnerability comprised large cultivation areas with minimal subsurface-water usage, except for areas where the number of dry days appeared to be the major factor for drought vulnerability. Damage caused by recurring droughts accumulated over time; thus, upland-field-oriented management may be required and can even be used in cases where insufficient drought information is available. Future studies can use the proposed method while considering assessment factors that describe upland field conditions.Y

Development of a Component-Based Modeling Framework for Agricultural Water-Resource Management

Because hydrologic responses of an agricultural watershed are influenced by many natural and man-made factors including pond/reservoir, management practices, and/or irrigation/drainage, strategies of hydrological modeling for the watershed must be case-dependent and thus carefully designed to effectively reflect their roles as critical hydrologic components in simulation processes. In this study, we propose a component-based modeling framework that accommodates a flexible modeling approach to consider a variety of hydrologic processes and management practices, especially irrigation-reservoir operation and paddy-farming practices, in watershed-scale modeling. The objectives of this study are twofold: to develop a COmponent-based Modeling Framework for Agricultural water-Resources Management (COMFARM) using an object-oriented programming technique, and to evaluate its applicability as a modeling tool to predict the responses of an agricultural watershed characterized with diverse land uses in a case study. COMFARM facilitates quick and easy development of watershed-specific hydrologic models by providing multiple interchangeable simulation routines for each hydrologic component considered. COMFARM is developed with the JAVA programming language, using Eclipse software. The framework developed in this study is applied to simulating hydrologic processes of the Seon-Am irrigation-district watershed consisting primarily of reservoir-irrigated rice paddies in South Korea. The application study clearly demonstrates the applicability of the framework as a convenient method to build models for hydrologic simulation of an agricultural watershed. The newly developed modeling framework, COMFARM is expected to serve as a useful tool in watershed management planning by allowing quick development of case-oriented analysis tools and evaluation of management scenarios customized to a specific watershed

Elliptical Polarization of Localized States in an Anisotropic Single GaAs Quantum Ring

Localized states in an anisotropic single GaAs quantum ring were investigated in terms of polarization dependence of micro-photoluminescence spectrum at 5K. Given four Stokes parameters measured with a pair of linear polarizers and waveplates, the elliptical polarization states of two different vertical confinement states (k=1 and k=2) were compared with phase, rotation, and ellipticity angles. While the polarized emission intensity of the k=2 states becomes enhanced along [1,1,0] compared to that along [1,1¯,0], the polarization asymmetry of the k=1 states shows the opposite result. We conclude the polarization state is determined by the shape of the lateral wavefunctions. In the k=2 state, crescent-like wavefunctions are strongly localized, but the k=1 state consists of two crescent-like wavefunctions, which are connected weakly through quantum tunneling

Evaluation of Agricultural Water Supply and Selection of Deficient Districts in Yeongsan River Basin of South Korea Considering Supply Priority

Considering the priority of water supply, agricultural water supply capacity downstream of the Yeongsan River Basin was evaluated in this study. The water balance was analyzed using the Please check all author names carefullyMODSIM-decision support system (MODSIM-DSS) to evaluate the agricultural water supply capacity. MODSIM-DSS can also be used to analyze the watershed demand status and agricultural water supply facilities. In this study, the watershed inflow and agricultural reservoir inflow (supply) data for each watershed were obtained using the SWAT outflow data. SWAT was calibrated and validated using 16-years (2005-2020) of daily streamflow data from one water level station and two weirs, by considering water withdrawal and return flows from agricultural, domestic, and industrial water use. The coefficient of determination (R-2) was analyzed as 0.50 to 0.80 at three stations. Then, water balance analyses were performed for 41 years (1980-2020) by applying the SWAT outflow results to MODSIM-DSS. The results showed that agricultural water shortages of 517.8 x 10(6) m(3), 520.0 x 10(6) m(3), 579.8 x 10(6) m(3), and 517.5 x 10(6) m(3), occurred in 1992, 1994, 1995, and 2015, respectively. The efficiencies of agricultural water supply for these years were 58.2%, 58.0%, 53.2%, and 58.2%, respectively, which were lower than the 40-year average of 84.5%.N

Correction: Kamruzzaman, M., et al. Evaluating the Impact of Climate Change on Paddy Water Balance Using APEX-Paddy Model. Water 2020, 12, 852

The authors wish to make the following corrections to this paper [...

A Comparison Study of Runoff Characteristics of Non-Point Source Pollution from Three Watersheds in South Korea

Three watersheds in Korea (Dochoncheon, Gongjicheon, Seolseongcheon) with different land cover characteristics were selected for non-point source pollution monitoring. Event mean concentration (EMC) was calculated, and runoff characteristics were compared through first-flushing and statistical analyses. The mean of the water quality parameters was the highest in Seolseongcheon during dry days among the three watersheds. EMCs of biochemical oxygen demand (BOD) and total nitrogen (TN) were higher in Dochoncheon and Gongjicheon during rainy days, respectively. The upper Seolseongchun watershed showed overall greater values of chemical oxygen demand (COD), suspended solids (SS), total organic carbon (TOC), and total phosphorus (TP). First-flush analyses indicated that SS had the strongest and TN had the weakest effects on the first flush. BOD was the highest in Dochoncheon (urban watershed) and increased with increased number of antecedent dry days. Rainfall intensity appeared to affect SS runoff strongly in Gongjicheon and Seolseongcheon. COD showed strong correlation with SS and TOC in all watersheds, and organic matter (COD and TOC) demonstrated high factor loads during dry and rainy days. Thus, organic matter−related factors were classified as the major factors in pollutant loads. TP and TN were separately classified during dry days in Gongjicheon and Seolseongcheon, whereas these were the secondary factors during rainfall when the influence of non-point pollution was substantial. Cluster analyses showed that the monitoring sites in Dochoncheon and Gongjicheon watersheds were closer than Seolseongcheon. As a result of the comparison of non-point source pollution runoff in the three watersheds, it was difficult to explain the non-point source pollution runoff by specific characteristics such as land cover. For science-based management of non-point pollution, it is necessary to obtain additional survey data considering the climatic, geographical and major industries