• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.509-509
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• 2022

Rice has always been the anchor of food security in the Philippines and the government is adamant about sustaining rice production by ensuring reliable irrigation water availability. Among the numerous irrigation schemes, the importance of the Pulangui River Irrigation System (PRIS) is undeniable, as it is the largest and primary irrigation source for rice production areas which are considered the food basket in Northern Mindanao. However, the ageing irrigation structures, unlined canals, long-standing water delivery systems, and climate change are compromising the performance of PRIS; and every year, during the dry and wet season, the maximum rice irrigable area is not achieved. From the field-scale water management perspective, untimely irrigation application, an unregulated roster of turn for irrigation among farmers, and the traditional practice of flooding the rice fields are the main causes of substantial water losses in conveyance, distribution, and farm application of irrigation water. Hence, proper irrigation scheduling is crucial to cultivate the maximum irrigable area by ensuring equity among the farmers and to increase the water use efficiency and yield. In this study, the FAO single crop coefficient approach was adopted to estimate rice water requirements, which were subsequently used to suggest appropriate irrigation schedules based on the recommended field-scale rice cultivation practices. The study results would improve the irrigation system management in the study area by facilitating in regulating the canal water flows and releases according to suggested irrigation schedules that could lead to increased benefited area, yield, and water efficiency without straining the available water resources.

• KCID journal
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• v.16 no.1
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• pp.94-99
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• 2009

• Korean Journal of Agricultural Science
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• v.47 no.1
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• pp.19-28
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• 2020

This study proposed a simple estimation method for irrigation return flow from paddy fields using the water balance model. The merit of this method is applicability to other paddy fields irrigated from agricultural reservoirs due to the simplicity compared with the previous monitoring based estimation method. It was assumed that the unused amount of irrigation water was the return flow which included the quick and delayed return flows. The amount of irrigation supply from a reservoir was estimated from the reservoir water balance with the storage rate and runoff model. It was also assumed that the infiltration was the main source of the delayed return flow and that the other delayed return flow was neglected. In this study, the amount of reservoir inflow and water demand from paddy field are calculated on a daily basis, and irrigation supply was calculated on 10-day basis, taking into account the uncertainty of the model and the reliability of the data. The regression rate was calculated on a yearly basis, and yearly data was computed by accumulating daily and 10-day data, considering that the recirculating water circulation cycle was relatively long. The proposed method was applied to the paddy blocks of the Jamhong and Seosan agricultural reservoirs and the results were acceptable.

• KCID journal
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• v.3 no.1
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• pp.40-52
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• 1996

This study was conducted to simulate long series of synthetic monthly flows by harmonic synthetic and harmonic regression models and to make a comparison of statistical parameters between observed and synthetic flows of six watersheds in Yeong San and Seo

• Journal of the Korean Society of Visualization
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• v.14 no.1
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• pp.40-45
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• 2016

Elimination of the smear layer and bacteria in the root canal is the most important in the endodontic treatment, and various irrigation devices have been developed. Nevertheless, it is hard to eliminate the smear layer and bacteria completely. In this paper, a micro bubble irrigation system has been developed for the root canal cleaning of tooth. Micro bubbles are generated when pressurized fluids passing through a porous material inside a hand-piece nozzle, and the bubbly flows excited by ultrasonic vibration are observed using a high-speed camera and a microscope. The results show that the diameter and number of bubbles increases with the applied pressure, and there found an optimum excitation frequency in order to minimize the bubble size. From in-vitro tests, it is also verified that the developed bubble irrigation system has the ability of antibacterial and infection removal. Thus, this biocompatible system would be well suited for root canal cleaning.

• Journal of Korean Society on Water Environment
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• v.35 no.2
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• pp.131-144
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• 2019

Climate Change affects the hydrological cycle in agricultural watersheds through rising air temperature and changing rainfall patterns. Agricultural watersheds in Korea are characterized by extensive paddy fields and intensive water use, a resource that is under stress from the changing climate. This study analyzed the effects of climate change on river flows for Geum Cheon and Eun-San Choen watershed using STREAM, a semi-distributed watershed model. In order to evaluate the performance and improve the reliability of the model, calibration and validation of the model was done for one flow observation point and three reservoir water storage ratio points. Climate change scenarios were based on RCP data provided by the Korea Meteorological Administration (KMA) and bias corrections were done using the Quantile Mapping method to minimize the uncertainties in the results produced by the climate model to the local scale. Because of water mass-balance, evapotranspiration tended to increase steadily with an increase in air temperature, while the increase in RCP 8.5 scenario resulted in higher RCP 4.5 scenario. The increase in evapotranspiration led to a decrease in the river flow, particularly the decrease in the surface runoff. In the paddy agricultural watershed, irrigation water demand is expected to increase despite an increase in rainfall owing to the high evapotranspiration rates occasioned by climate change.

• Magazine of the Korean Society of Agricultural Engineers
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• v.32 no.3
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• pp.47-55
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• 1990

An adaptive algorithm was applied to forecast daily stream flows in real time using rainfall data. A three-component tank model was selected to simulate the flows and its time-variant parameters were self-calibrated with updated data using a parameter optimization scheme, golden section search method. The resulting adaptive model, APTANK, was applied to six watersheds, ranging from 0.47 to 33.62 km$^2$ size and the simulated daily streamflows were compared with the measured. The simulation results were in good agreement with the field data. APTANK is found to be applied to real-time flow simulation purposes such as a tool for irrigation water resources management and operations. The model is particularly good to simulate streamflows on dry days as compared to wet days having runoff-induced precipitation.

• Korean Journal of Agricultural Science
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• v.37 no.3
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• pp.481-490
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• 2010

Baekgog reservoir is located in Jincheon county, Chungbuk province, of which full water levels will be heightened from EL. 100.1 m to EL. 102.1 m, and total storages from 21.75 $Mm^3$ to 26.67 $Mm^3$. The simulation for reservoir inflow was conducted by DAWAST model. The annual average irrigation water was estimated to 33.19 $Mm^3$ supplied to 2,975 ha and the instream flows could be allocated with 0.14 mm/d from October to April with annual average of 2.52 $Mm^3$. The operation rule curve was drawn using inflow, irrigation, and instream flow requirements data. The reservoir water storage was simulated on a daily basis in case of both normal and withdrawal limit operation. In case of normal operation, the annual average irrigation water supply increased from 31.95 $Mm^3$ to 33.32 $Mm^3$, the instream water supply from 2.40 $Mm^3$ to 2.44 $Mm^3$, the water storages from 15.74 $Mm^3$ to 19.88 $Mm^3$, and the water supply reliability from 77.3 % to 81.6 %. In case of operation with withdrawal limit, the amount of instream water supply was 2.52 $Mm^3$ from reservoir regardless of the condition while the water storage increased from 16.77 $Mm^3$ to 20.65 $Mm^3$. The irrigation water supply capacity was appropriate for the case of normal operation with 2 m heightened condition. The present instream water supply capacity was 35,000 $m^3$/d (6.86 $Mm^3$/y) while 42,000 $m^3$/d (8.36 $Mm^3$/y) in 2 m heightened condition in case of withdrawal limit operation.

• Journal of The Korean Society of Agricultural Engineers
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• v.55 no.6
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• pp.167-175
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• 2013

The objective of this study was to investigate the nutrient load balance in the reservoir irrigated paddy block during growing seasons. Idong reservoir irrigation paddy block of 10.3 ha in size was selected to collect hydrologic and water quality data. Irrigation, canal flows, and paddy field drainage were measured using a water level gauge, while water samples were collected and analysed for water quality. The water balance analysis showed that 81 % and 75 % of total outflow were through paddy and irrigation canal drainage during 2011 and 2012, respectively. The water quality of paddy field drainage varied greatly depending on rice cultivation stage ranging from 0.05 to 24.55 mg/L and from 0.01 to 0.76 mg/L for T-N and T-P, correspondently. Paddy field drainage loads during May through June account for 64 % and 76 % in 2012 and 2013, while 82 % and 81 % for T-P in 2011 and 2012, respectively. The Pearson correlation analysis showed that rainfall was significantly correlated with nutrient loads during July through August due to runoff, and irrigation was related with nutrient loads of drainage during some period of July through September due to irrigation return flow. This study results showed characteristics of inflow and outflow nutrient loads from plentiful irrigated paddy block.

• KCID journal
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• v.2 no.1
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• pp.45-56
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• 1995

본 연구에서는 미국 West Virgini주 동북부에 위치한 Cheat River Basin 일원에 1985. 11월에 발생한 대홍수를 HEC-1 Computer Model로 재현시켰다. 전체 유역을 수문 및 지형 특성에 따라 각 소유역으로 나누어 각소유역에 대해 지표면유출을 계산하였다. 적용된 단위도는 본 유역의 지형 특성을 고려 Snyder's Unit Hydrograph를 이용하였다. Cheat River 전체에 대한 홍수조절 계획이 본 HEC-1