• Proceedings of the Korea Water Resources Association Conference
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• 2020.06a
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• pp.62-62
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• 2020

기후변화에 따른 기온과 강수량 등 기상조건의 변화로 인하여 기상·자연재해뿐만 아니라 작물의 수확량 감소, 병해충 및 잡초 발생의 증가, 흙과 물의 부족, 재배 적지의 변화와 같은 농업인프라 또한 기후변화의 피해가 발생하고 있다. 농업수자원 측면에서, 농어촌용수는 자연적으로 내리는 강우를 직접 작물성장에 사용하기 때문에 기후변화에 특히 민감하다. 또한 기온의 변화는 농업용 저수지의 증발량 및 유입량의 변화를 일으키며 이러한 변화는 곧 저수위 및 저수량의 변화를 유발하여 농업·농촌 수자원 관리의 어려움으로 이어질 것으로 판단된다. 이에 따라, 기후변화에 따라 예상되는 대규모 자연재해를 대비하고 기후변화에 효율적으로 대처하기 위해서는 체계적이고 과학적인 기상·기후 정보의 활용이 중요하며 기후변화로 인한 농업 기상재해 최소화를 위해서는 다양한 기후변화 시나리오를 활용하여 미래 기상·기후의 변화에 대한 경향성 분석 및 예측을 통한 영향 평가가 필요하다. 본 연구는 전국 농어촌용수구역 517개 용수구역 중 접경·도시·도서지역을 제외한 511개 용수구역을 대상으로 증발산량 산정이 가능한 RCP 8.5 기후변화 시나리오 9개를 지역별로 상대적인 기후사상의 크기와 빈도 및 강도 정량적으로 평가할 수 있는 STARDEX 극한지수를 적용하여 시나리오의 미래 기상전망을 실시하였다. 기상전망 결과를 이용하여 Kendall-Tau 검정을 통해 시나리오의 순위를 적용하여 각 시나리오의 미래기후변화의 상대적인 정도를 평가하였고, 9개의 기후변화 시나리오를 DIROM(Daily Irrigation Reservoir Operation Model) 모형에 적용하여 기후변화 시나리오의 높은 불확실성을 고려한 미래 농어촌용수구역의 농어촌용수 필요수량 변화를 지역적으로 분석하고 미래 농어촌용수량의 최대·최소 변화 범위를 제시하였다.

• Proceedings of the Korea Water Resources Association Conference
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• 2020.06a
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• pp.44-44
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• 2020

최근 기후변화의 기온 상승 및 강수량 증가의 영향으로 농업용수 수요량이 증가하고 있다. 이에 따라 농업용수의 약 60%를 공급하는 농업용 저수지의 용수 수요의 변화와 그에 따른 공급능력에 대한 평가가 필수적이다(한국농어촌공사, 2019). 본 연구에서는 기후변화 시나리오를 기반으로 농업용저수지 물수지 모의 프로그램인 DIROM(Daily Irrigation Reservoir Operation Model) 모형을 활용하여 우리나라 미래 필요수량 변화에 따른 농어촌용수 수요 변화를 분석하고, 가뭄대책단계별 관리수위를 활용해 공급능력을 평가하고자 한다. 필요수량 분석을 위해 2018년 농업생산 기반시설 통계연보의 논면적 자료 및 농어촌용수 이용 합리화계획(2015~2024)의 수로손실, 삼투량 자료를 구축하였고, 공급능력 평가를 위해 한국농어촌공사 관할 3,666개 저수지 중 저수지 시설규모, 수혜면적 등을 고려하여 선정한 426개 저수지를 대상으로 농업기반시설관리시스템(RIMS)의 저수지 제원, 내용적 곡선 및 평년저수율 자료를 수집하였다. 기후변화 시나리오는 기상청으로부터 제공받은 HadGEM3-RA RCP(Representative Concentration Pathway) 8.5 시나리오를 이용하였으며 기후변화 시나리오 기간을 S1(2021-2040), S2(2041-2070), S3(2071-2099)로 구분하여 분석하였다. 전국 필요수량을 산정한 결과 평년(1981-2005) 대비 S1, S2, S3에서 각각 12.0%, 9.1% 16.4 % 증가하여 미래로 갈수록 증가하는 경향이 나타났다. 426개 저수지에 대한 물수지 분석을 통해 저수율을 산정하고 평년저수율을 통해 산정한 가뭄대책단계별 관리수위를 기준으로 용수공급능력을 파악한 결과 저수율이 40% 미만 일이 평년대비 S1, S2, S3에서 15.9일, 11.8일, 18.1일로 증가하였다. 본 연구의 결과는 미래 기후변화에 따른 농업용 저수지 용수관리계획 및 의사결정 자료로 활용 될 것이라 판단된다.

• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.483-483
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• 2022

댐과 저수지의 운영 최적화를 위한 수문학적 예보는 현재 수동적인 댐 운영이 주를 이루면서 활용도가 높지 않다. 불확실한 기후변화나 기후재난 상황에서 우리 사회에 악영향을 최소화하기 위해 선제적으로 대응/대비할 수 있는 댐 운영 방안이 불가피하다. 강우량 예측 기술은 기후변화로 인해 제한적인 상황이다. 실례로, 2020년 8월에 섬진강의 댐이 극심한 집중 강우로 인해 무너지는 사태가 발생하였고 이로 인해 지역사회에 막대한 경제적 피해가 발생하였다. 선제적 댐 방류량 운영 기술은 또한 환경적인 변화로 인한 영향을 완화하기 위해 필요한 것이다. 제한적인 기상 예보 기술을 극복하고자 심화학습이나 강화학습 같은 인공지능 모델들의 활용성에 대한 연구가 시도되고 있다. 따라서 본 연구는 섬진강 댐의 시간당 수문 데이터를 이용하여 댐 운영을 위한 심화학습 모델을 개발하고 그 활용도를 평가하였다. 댐 운영을 위한 심화학습 모델로서 시계열 데이터 예측에 적합한 Long Sort Term Memory(LSTM)과 Gated Recurrent Unit(GRU) 알고리즘을 구축하고 댐 수위를 예측하였다. 분석 자료는 WAMIS에서 제공하는 2000년부터 2021년까지의 시간당 데이터를 사용하였다. 입력 데이터로서 시간당 유입량, 강우량과 방류량을, 출력 데이터로서 시간당 수위 자료를 각각 사용하였으며. 결정계수(R2 Score)를 통해 모델의 예측 성능을 평가하였다. 댐 수위 예측값 개선을 위해 하이퍼파라미터의 '최적값'이 존재하는 범위를 줄여나가는 하이퍼파라미터 최적화를 두 가지 방법으로 진행하였다. 첫 번째 방법은 수동적 탐색(Manual Search) 방법으로 Sequence Length를 24, 48, 72시간, Hidden Layer를 1, 3, 5개로 설정하여 하이퍼파라미터의 조합에 따른 LSTM와 GRU의 민감도를 평가하였다. 두 번째 방법은 Grid Search로 최적의 하이퍼파라미터를 찾았다. 이 두가지 방법에서는 같은 하이퍼파라미터 안에서 GRU가 LSTM에 비해 더 높은 예측 정확도를 보였고 Sequence Length가 높을수록 정확도가 높아지는 경향을 보였다. Manual Search 방법의 경우 R2가 최대 0.72의 정확도를 보였고 Grid Search 방법의 경우 R2가 0.79의 정확도를 보였다. 본 연구 결과는 가뭄과 홍수와 같은 물 재해에 사전 대응하고 기후변화에 적응할 수 있는 댐 운영 개선에 도움을 줄 수 있을 것으로 판단된다.

• Korean Journal of Ecology and Environment
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• v.35 no.4 s.100
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• pp.285-294
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• 2002

The purpose of this study was to evaluate the relationships between purification characteristics and hydraulic conditions, and to clarify the basic and essential factors required to be considered in the construction and management of artificial wetland system for the improvement of reservoir water quality. The artificial wetland system was composed of a pumping station and six sequential plants beds with five species of macrophytes: Oenanthe javanica, Acorus calamus, Zizania latifolia, Typha angustifolia, and Phragmites australis. The system was operated on free surface-flow system, and operation conditions were $3,444-4,156\; m^3/d$ of inflow rate, 0.5-2.0 hr of HRT, 0.1-0.2 m of water depth, 6.0-9.4 m/d of hydraulic loading, and relatively low nutrients concentration (0.224-2.462 mgN/L, 0.145-0.164 mgP/L) of inflow water. The mean purification efficiencies of TN ranged from 12.1% to 14.3% by showing the highest efficiency at the Phragmites australis bed, and these of TP were 6.3-9.5% by showing the similar ranges of efficiencies among all species. The mean purification efficiencies of SS and Chl-A ranged from 17.4% to 38.5% and from 12.0% to 20.2%, respectively, and the Oenanthe javanica bed showed the highest efficiency with higher concentration of influent than others. The mean purification amount per day of each pollutant were $9.8-4.1\;g{\cdot}m^{-2}{\cdot}d^{-1}$ in BOD, $1.299-2.343\;g{\cdot}m^{-2}{\cdot}d^{-1}$ in TN, $0.085-1.821\;g{\cdot}m^{-2}{\cdot}d^{-1}$ in TP, $17.9-111.6\;g{\cdot}m^{-2}{\cdot}d^{-1}$ in SS and $0.011-0.094\;g{\cdot}m^{-2}{\cdot}d^{-1}$ in Chl-a. The purification amount per day of TN revealed the hi링hest level at the Zizania latifolia bed, and TP showed at the Acrous calamus bed. SS and Chl-a, as particulate materials, revealed the highest purification amount per day at the Oenanthe javanica bed that was high on the whole parameters. It was estimated that the purification amount per day was increased with the high concentration of influent and shoot density of macrophytes, as was shown in the purification efficiency. Correlation coefficients between purification efficiencies and hydraulic conditions (HRT and inflow rate) were 0.016-0.731 of $R^2$ in terms of HRT, and 0.015-0.868 of $R^2$ daily inflow rate. Correlation coefficients of purification amounts per day with hydraulic conditions were 0.173-0.763 of Ra in terms of HRT, and 0.209-0.770 daily inflow rate. Among the correlation coefficients between purification efficiency and hydraulic condition, the percentages of over 0.5 range of $R^2$ were 20% in HRT and in daily inflow rate. However, the percentages of over 0.5 range of correlation coefficients ($R^2$) between purification amount per day and hydraulic conditions were 53% in HRT and 73% in daily inflow rate. The relationships between purificationamount per day and hydraulic condition were more significant than those of purifi-cation efficiency. In this study, high hydraulic conditions (HRT and inflow rate) are not likely to affect significantly the purification efficiency of nutrient. Therefore, the emphasis should be on the purification amounts per day with high hydraulicloadings (HRT and inflow rate) for the improvement of eutrophic reservoir withrelatively low nutrients concentration and large quantity to be treated.

• Journal of the Korean Society of Hazard Mitigation
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• v.8 no.6
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• pp.121-128
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• 2008

Instream flows are defined as the stream flows needed to protect and preserve instream resources and values. They are supplied by the essential discharge for maintaining the channel. However, due to the lack of precipitation during the dry season, which is usually between the months of January and April, natural flows are not enough for the instream flows, thus leaving the dams at a shortage. In this paper, the method which will be discussed will show a physical way to improve water quality by the dilution of water that is supplied from a reservoir or dam, and how it is analyzed at the Han River basin. For the sake of this analysis, the basin has been divided into 33 catchments. Each catchment's natural flow has been simulated by SWAT-K, and the future water demand has been estimated using statistical data. It has also been assumed that the Han River basin has two large reservoirs(Chung-ju dam, and So-yang dam). The supply of potential discharge has been calculated using a case of water separately from each dam, as well as supply water from both dams.

• Journal of Environmental Health Sciences
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• v.43 no.2
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• pp.143-156
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• 2017

The purpose of this study was to investigate water quality through a field survey at six floor fountain sites. The floor fountain facilities were designed and operated in such a way that tap water was stored in a water tank and recycled repeatedly. The water tank was cleaned once or twice per week in the summer. The number of facility users was low during the day due to sweltering heat, but up to 40 people, mainly children, were using them around 8 pm. Since the operation time was as short as 30 minutes, it is considered necessary to extend it for at least one hour for the number of users. As a result of the water quality test of the reservoir tank prior to operation after cleaning, it was measured to be within drinking water quality standards at the six facilities. As a result of the water quality test after use, ammonia nitrogen was measured to be 1.45 mg/L at Site IV. This exceeded the drinking water quality standard of 0.5 mg/L. In the case of turbidity, two cases exceed at 7.38 and 4.52 NTU when applying 4 NTU as the water quality standard for waterscape facilities. Twenty-eight cases exceed the standard of drinking water quality. The result of microbiological tests, at five sites excepting Site I, where disinfectant was injected, was that the maximum total colony count was 180,000 CFU/mL, total coliforms was 2,100,000 CFU/100 mL, fecal coliforms was 4,600 CFU/100 mL, Escherichia coli was 170 MPN/100 mL and Enterococcus was 100 CFU/100 mL. This exceeded the water quality standards of drinking water. Children are very likely to inhale because the water spews from below and falls from above, so it is necessary to apply water quality standards for ammonia nitrogen, turbidity and microbes. Current floor fountain facilities are highly susceptible to disease caused by microbial contamination because of water cycling and reuse, so it is necessary to change the water every day, clean the water tank, and perform chlorination. Therefore, it is necessary to inject calcium hypochlorite according to the free chlorine water quality standard of swimming pools with a different water tank capacity. In addition, facilities should be improved to prevent the reuse of water by installing the water tank at a separate location.

• Journal of the Korean Institute of Gas
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• v.27 no.2
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• pp.7-15
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• 2023

The electric submersible pump (ESP) has been operating in production wells around the world because of its high applicability and operational efficiency among artificial lift techniques. When operating an ESP in a reservoir, variables such as temperature, pressure, gas/oil ratio, and flow rate are factors that affect ESP performance. In particular, free gas in the production fluid is a major factor that reduces the life and operational efficiency of ESP. This study presents the flow loop system which can implement the performance and damage tests of ESP considering field operating conditions to quantitatively analyze the variables that affect ESP performance. The developed apparatus in an integrated system that can diagnose the failure and causes of ESP, and detect leak of tubing by linking ESP and tubing as one system. In this study, the flow conditions for stable operation of ESP were identified through single phase and two phase flow experiments related to evaluation for the performance of ESP. The results provide the basic data to develop the failure prediction and diagnosis program of ESP, and are expected to be used for real-time monitoring for optimal operating conditions and failure diagnosis for ESP operation.

• Journal of Gastric Cancer
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• v.4 no.4
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• pp.242-251
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• 2004

Purpose: Recently, because of the increasing numbers of early gastric cancer patients and improvements in their survivals, greater attention has been directed towards the quality of life and nutritional status of gastric cancer patients after surgery. However, conventional reconstructions, Billroth- I, -II (B-I and B-II) or Roux-en-Y, have proven to have certain limitations, such as a small reservoir, and a malabsorption for iron, fat, calcium, and carotene. To overcome these limitations, we used a jejunal pouch interposition(JPI) after a distal gastrectomy not only to substitute for the small reservoir but also to maintain a physiologic pathway for ingested foods. Materials and Methods: A total of 196 gastric cancer patients who underwent a distal gastrectomy between March 2001 and February 2004 were divided into 3 groups: JPI group (n=100), B-I group (n=29), and B-II group (n=67). We assessed the patient's nutritional status, gastric emptying time, and gastrofiberscopic findings. Results: The percents of body weight loss at 6 months, 1 year, and 2 years postoperatively in the JPI group ($5.14\%,\;3.01\%,\;2.37\%$) were significantly less than those of the conventional B-I ($8.41\%,\;6.69\%,\;5.90\%$) and B-II groups ($7.50\%,\;7.65\%,\;5.86\%$) (P=0.011, 0.000, 0.013). The laboratory findings showed no significant differences between the 3 groups, except for a higher total protein level in the JPI group after 6 months postoperatively. Especially, stage I and II cancers in the JPI group showed much higher total protein levels after 1 year postoperatively. The gastric emptying times in the $\^{99m}$Tc- semisolid scans at 6 months, 1 year, and 2 years postoperatively were 102.5, 83.1, and 58.1 minutes in the JPI group, 95.5, 92.0, and 58.5 minutes in the B-I group, and 53.9, 69.1, and 50.2 minutes in the B-II group, respectively. Also, the symptomatic gastric stasis detected with a gastrofiberscope during the early postoperative period (6 months) was gradually improved. Conclusion: From a nutritional aspect, a jejunal pouch interposition after a distal gastrectomy could be an alternative reconstruction method, especially in stage I and II gastric cancer patients, in spite of the longer operation time and the probable delayed gastric emptying.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.5
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• pp.463-471
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• 2006

Electrical resistivity surveys were conducted at areas of abandoned landfills in Cheonan and Wonju. Geology and extent of leachate migration around the landfills were evaluated with collected resistivity data by 2-D and 3-D resistivity inverse modeling. The Cheonan landfill is located above the paddy fields and the resistivity survey lines were crossed to examine possible pollution at the paddy fields by leakage of the landfill leachate. In Wonju, the landfill and the downgradient paddy fields are divided by a concrete barrier wall. At the bottom of the landfill, there is a leachate settlement system, which has not been in operation. To evaluate leachate leakage into the paddy fields, a total of 4 survey lines were used. According to the resistivity survey results, the landfill leachate in Cheonan appeared to be restricted only within the interior of the landfill, not to migrate into the subsurface of the paddy fields. These results are well consistent with electrical conductivity values of groundwaters obtained from a periodic analysis of water qualities. In Wonju, however, it was inferred that the leachate emanating from the landfill migrated beneath the abandoned leachate settlement system and the leachate would reach the downgradient paddy fields. Low resistivity area was observed in the old reservoir area and it appeared to be derived from convergence of groundwater flows from the surrounding valley and the moist wet land. In addition, groundwater flow into the paddy fields occurs beneath the old reservoir embankment at depths of $7{\sim}8m$. This paper reports details of the resistivity surveys for the uncontrolled landfills.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.4
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• pp.2343-2348
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• 2014

Main ground net of power plant is formed to protect human body from increase in potential gradient caused by grounding current during ground fault. Calculations during ground design are generally performed according to IEEE Std-80-2000 (Kepco Design Standard 2602). However, it is difficult to apply this Standard to water environment, and a grounding technology is required to secure grounding resistance of floating photovoltaic system. Therefore the aim of this paper is to investigate and analyze ground resistivity on the water surface and underwater of reservoir using Wenner 4-pin method, a general method of measuring ground resistivity. Also, grounding resistance of floating photovoltaic systems currently in operation was measured and analyzed using the voltage drop method suggested in the international standard (IEEE Std-81) to propose a grounding method for stable grounding of floating photovoltaic system. The resistivity at 1m below the surface of water ($126.3969[{\Omega}{\cdot}m]$) is mostly higher than resistivity at the river bed ($97.5713[{\Omega}{\cdot}m]$). Also the proposed grounding anchor method was determined as the most effective method of securing stable grounding resistance in floating photovoltaic systems and is expected to be utilized as a ground method for future floating photovoltaic generation systems.