최진용 Choi Jin-yong , 홍은미 Hong Eun Mi , 남원호 Nam Won Ho , 유승환 Yoo Seung-hwan

DOI: JKWST Vol.53(No.4) 1-9, 2011

---

Forest area covers 64 % of the national land of Korea and the forest plays a pivotal role in the hydrological process such as flood, drought, runoff, infiltration, evapotranspiration, etc. In this study, soil moisture monitoring for conifer forest in experimental forest of Seoul National University has been conducted using FDR (Frequency Domain Reflection) for 6 different soil layers, 10, 20, 30, 60, 90 and 120 cm during 2009～2010, and precipitation data was collected from nearby AWS (Automatic Weather Station). Soil moisture monitoring data were used to estimate soil moisture recession constant (SMRC) for analyzing soil moisture recession characteristics. From the results, empirical soil moisture recession equations were estimated and validated to determine the feasibility of the result, and soil moisture contents of measured and calculated showed a similar tendency from April to November. Thus, the results can be applied for soil moisture estimation and provided the basic knowledge in forest soil moisture consumption. Nevertheless, this approach demonstrated applicability limitations during winter and early spring season due to freezing and melting of snow and ice causing peculiar change of soil moisture contents.

전지홍 Jeon Ji-hong

DOI: JKWST Vol.53(No.4) 11-19, 2011

---

PADDIMOD2 was deloped to estimate nonpoint source pollution from paddy rice fields. The PADDIMOD2 was enhanced to estimate runoff and pollutant load during non-growing as well as growing season and to be easily used for public by development of Excel based system. Nutrient concentration and hydrology were based on Dirac delta function and continuous source function, and tank model for growing season and Event Mean Concentrations (EMCs) and SCS-Curve Number method for non-growing season. The PADDIMOD2 consists of three main component (input data, parameters data, and output data) by including eight Excel spread sheets. As a result of model application, total precipitation and irrigation were 1,051.7 mm and 439.2 mm, respectivley and surface runoff and water loss including infiltration and evapotranspiration were 463.0 mm and 947.9 mm, respectively. Annual nutrient loadings of T-N and T-P from study area were 6.7 kg/㎢/day and 0.5 kg/㎢/day, respectively. Development of PADDIMOD2 was focused on minimizing input data and maximizing user friendly system and is expected to be useful tool to evaluate various non-structure BMPs and estimate unit load from paddy rice fields for application at Korean TMDL.

봉태호 Bong Tae-ho , 김성필 Kim Seong-pil , 허준 Heo Joon , 손영환 Son Young-hwan

DOI: JKWST Vol.53(No.4) 21-27, 2011

---

Soil stress distribution under loading is one of the important problems in civil engineering. Many models have been proposed to interpret the stress distribution in soil and most models assume that the soil is homogeneous and isotropic. Therefore, the actual stress distribution may be different. In addition, With the increase of the top load, soil stress does not increase linearly. In this study, vertical stress changes in sandy soil according to top load increase were measured through experiments. Experimental results, vertical soil stress due to top load increase showed an initial nonlinear behavior and when the load increases to some extent, vertical soil stress showed a linear behavior. α value obtained by existing theories always 1.00. But, α value by experiment was observed from 0.91 to 1.22 and α value was increased with increasing distance from the loading plate.

신민환 Shin Min Hwan , 원철희 Won Chul Hee , 박운지 Park Woon Ji , 최용훈 Choi Young Hun , 장정렬 Jang Jeong Ryeol , 임경재 Lim Kyoung Jae , 최중대 Choi Joong Dae

DOI: JKWST Vol.53(No.4) 29-37, 2011

---

Effect of rice straw mat and wood shaves on the reduction of runoff and nonpoint source (NPS) pollution loads from field plots were experimentally studied. Three runoff plots of 5×22 m in size and 3 % in slope were prepared on a loamy sand field. Each plot was equipped with a flume to measure runoff and collect water samples. Experimental treatments of surface cover were bare, wood shaves (1,000 kg/ha) and rice straw mat cover (3,000 kg/ha). Under radish was cultivation. During the growing season of the radish, three rainfall-runoff events were monitored. Effect of wood shaves and straw mat cover on runoff reduction was 4～30 % and 33～75 % respectively compared to control. The effect on NPS pollution reduction was 36.8 and 64.3 % in BOD, 41.1 and 80.8 % in SS, 34.0 and 56.1 % in TP and 28.0 and 56.6 % in TN respectively. It was analyzed that the reduction of runoff and NPS pollution were mainly contributed by the decrease of rainfall energy impact and flow velocity and the increase of infiltration due to the surface cover materials. Rice straw mat showed very stable soil cover while large portion of wood shaves were lost during heavy storm events. It was concluded that straw mat was an efficient cover material to reduce NPS pollution from upland fields.

윤동균 Yun Dong Koun , 정상옥 Chung Sang Ok , 김성준 Kim Seong Joon

DOI: JKWST Vol.53(No.4) 39-47, 2011

---

The aim of the study is to predict potential evapotranspiration and crop water requirement using meteorological data from MIROC3.2 with A1B scenario. Increase of evapotranspiration due to temperature rise can be observed out of the analysis, while effective rainfall decreased. The evapotranspiration elevation results in large amount of crop water requirement in the paddy farming. It can be seen that rainfall intensification at non-irrigation period brings effective rainfall decrease, while contributes to higher demand of crop water at irrigation period. It is necessary to secure additional water resources to adapt the climate change. It is expected that estimation on potentialevapotranspiration in this study can be used for formulation of master plan of water resources.

박운지 Park Woon Ji , 최용훈 Choi Yong Hun , 신민환 Shin Min Hwan , 원철희 Won Chul Hee , 박기욱 Park Ki Wook , 최중대 Choi Joong Dae

DOI: JKWST Vol.53(No.4) 49-57, 2011

---

The objective of this study was to experimentally investigate the feasibility of SRI (system of rice intensification) in Korean rice farming. Eight experimental plots of 5×15 m in size were prepared on an existing rice field of loam soil. Spacing was 30×15 cm (conventional treatment: CT), 30×30 cm, 40×40 cm and 50×50 cm, respectively. CT were flooded and SRI plots irrigated intermittently 3 to 5 day interval during cultivation. Organic matter content and pH of the soil were 2.5±0.03 % and 6.1±0.2, respectively, before the cultivation. The highest number of tillers and height of the plant were measured at 50×50 cm plots. The height and number of tillers and height in 50×50 cm plots were 10 cm and 1.5 times more than CT. Average irrigation supply to SRI and CT was 243.2 mm and 547.3 mm, respectively. It meant that the reduction of irrigation water in SRI plots over CT was estimated to 55.6 %. Therefore SRI was concluded to have a good enough possibility to be applied in South Korea because it was proven to be more effective in reduction of irrigation water and crop cultivation compare to the CT.

성충현 Seong Choung Hyun , 김성재 Kim Sung Jae , 김성민 Kim Sung Min , 김상민 Kim Sang Min

DOI: JKWST Vol.53(No.4) 59-65, 2011

---

The purpose of this study was to analyze the water quality change when wastewater applied to study paddy fields. CREAMS-PADDY (Chemical, Runoff and Erosion from Agricultural Management System) model was used to estimate the field-scale water quality. Simulated results were compared with observed data monitored from Byeongjeom study paddy fields which is located near the Suwon sewage treatment plant in Gyeonggi-do. Significance analysis was performed for the three different irrigation water quality level and five fertilizer reduction scenarios using LSD (Least Significant Difference) and DMRT (Duncan's Multiple Range Test). Total nitrogen was found to be significant for both irrigation water quality level and fertilizer reduction while total phosphorus was not. Annual drainage load for total nitrogen was reduced by 66∼92 % compared to irrigation load when treated wastewater irrigated to study paddy fields from 2002 to 2007. Total phosphorus was reduced by 70∼86 %.

정한석 Jeong Han Seok , 성충현 Seong Choung Hyun , 장태일 Jang Tae Il , 정기웅 Jung Ki Woong , 강문성 Kang Moon Seong , 박승우 Park Seung Woo

DOI: JKWST Vol.53(No.4) 67-74, 2011

---

The objectives of this study were to assess the rice yields and evaluate fertilizer reduction effect of reclaimed wastewater irrigation in paddy fields using the Decision Support System for Agrotechnology Transfer (DSSAT) v4.5 model. The experimental plots were designed, which was located near the Suwon wastewater treatment plant in Gyeonggi-do, Korea. The rice yield, irrigation amount, irrigation water quality and soil data were monitored and collected between 2006 and 2009. The DSSAT model was calibrated and validated with observed data. The methods that were used to evaluate this model were the root mean square error (RMSE), normalized root mean square error (nRMSE), and index of agreement (d). The values of RMSE, nRMSE, and d ranged from 145 to 789 kg ha^-1, 3.0 to 13.3 %, and 0.90 to 0.95 for the calibration period, respectively and represented from 91 to 538 kg ha^-1, 2.0 to 10.4 %, 0.94 to 0.98 for the validation period, respectively. Overall, this model showed good agreement with observed data of rice yields irrigated with reclaimed wastewater. The fertilizer reduction effect in paddy field of reclaimed wastewater irrigation was assessed about 60 % in 2008 and 40 % in 2009.