• Title, Summary, Keyword: hydrologic condition

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Watershed Scale Drought Assessment using Soil Moisture Index (토양수분지수를 이용한 유역단위 가뭄 평가)

  • Kim, Ok-Kyoung;Choi, Jin-Yong;Jang, Min-Won;Yoo, Seung-Hwan;Nam, Won-Ho;Lee, Joo-Heon;Noh, Jae-Kyoung
    • Journal of The Korean Society of Agricultural Engineers
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    • v.48 no.6
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    • pp.3-13
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    • 2006
  • Although the drought impacts are comparably not catastrophic, the results from the drought are fatal in various social and economical aspects. Different from other natural hazards including floods, drought advances slowly and spreads widely, so that the preparedness is quite important and effective to mitigate the impacts from drought. Soil moisture depletion directly resulted from rainfall shortage is highly related with drought, especially for crops and vegetations, therefore a drought can be evaluated using soil moisture conditions. In this study, SMI (Soil Moisture Index) was developed to measure a drought condition using soil moisture model and frequency analysis for return periods. Runs theory was applied to quantify the soil moisture depletions for the drought condition in terms of severity, magnitude and duration. In 1994, 1995, 2000, and 2001, Korea had experienced several severe droughts, so the SMI developed was applied to evaluate applicability in the mid-range hydrologic unit watershed scale. From the results, SMI demonstrated the drought conditions with a quite sensitive manner and can be used as an indicator to measure a drought condition.

Hydrologic Regimes Analyses on Down Stream Effects of the Young Chun Dam by Indicators of Hydrologic Alterations (수문변화 지표법에 의한 영천댐이 하류하천에 미치는 유황변화 분석)

  • Park, Bong-Jin;Kim, Joon-Tae;Jang, Chang-Lae;Jung, Kwan-Sue
    • Journal of Korea Water Resources Association
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    • v.41 no.2
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    • pp.163-172
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    • 2008
  • Hydrologic regimes play a major role in determining the biotic composition, structure, and function of river ecosystem. In this study, hydrologic regimes were analyzed on down stream effects of the Young-Chun dam construction using the Indicators of Hydrologic Alterations(IHA). The analysis results were as follows ; (1) Monthly mean flows were decreased during drought and flood season on the pre and post dam, (2) Magnitude and Duration of Annual Exterm Conditions, annual minima 1-day means was $3.48m^3/sec$, $0.89m^3/sec$ and annual maxima 1-day mean was $833.1m^3/sec$, $672.1m^3/sec$ on the pre and post dam (3) Timing of Annual Exterm conditions, Julian date of the annual minima 1-day means was 180th(June) in the pre dam, 257th(September) in the post dam, Julian date of the annual maxima 1-day means was 209th(July) in the pre dam, 217th(August) in the post dam, (4) Frequency and Duration of High and Low Pulse, Low Puls counts and duration were 3 times and 23 days in the pre dam, High Pulse counts and duration were 4 times and 2 days in the pre dam. (5) Rate and Frequency of Water Condition Changes, rise rates was 39.27 %, 19.36 % and fall rates -15.85 %, -8.16 % in the pre and post dam, respectively (6) Coefficient of Variation, annual exteram water conditions were decreased from 0.9054 to 0.6314 and from 1.0440 to 0.9617, Timing of Annual Exterm conditions were incereased for minima flow from 0.269 to 0.282, for maxima form 0.069 to 0.153.

Development of a Monitoring Technique of Dryness and Wetness in Watershed using Climatic Water Budget (기후학적 물수지에 의한 유역의 건조 및 습윤 상황 감시 기법 개발)

  • Shin, Sha-Chul;Hwang, Man-Ha;Ko, Ick-Hwan
    • Journal of Korea Water Resources Association
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    • v.41 no.2
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    • pp.173-184
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    • 2008
  • Climatic water balance has been applied to obtain quantity of various hydrologic components. Hydrologic information is estimated by comparison between rainfall and evapotranspiration under complex terrain condition. Water deficit is defined as that subtraction of actual supply from climatic demand. The water deficit will occur, when monthly evapotranspiration exceed monthly rainfall. Contrary water surplus is defined as that surplus water after meeting the demand by plants. The water surplus will be occurred when monthly rainfall exceeds monthly evapotranspiration. Finally, the discrete moisture indices were calculated and mapped for the whole watershed to estimate dryness and wetness status using the climatic water balance approach. The result of this study can properly interpret the real drought and non drought. Based upon the results, it can be concluded that the climatic water balance model is useful to monitor water conditions for the watershed.

Spatial Analysis of Nonpoint Source Pollutant Loading from the Imha dam Watershed using L-THIA (L-THIA를 이용한 낙동강수계 임하댐유역 비점오염원의 공간적 분포해석)

  • Jeon, Ji-Hong;Cha, Daniel K.;Choi, Donghyuk;Kim, Tae-Dong
    • Journal of The Korean Society of Agricultural Engineers
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    • v.55 no.1
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    • pp.17-29
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    • 2013
  • Long-Term Hydrologic Impact Assessment (L-THIA) model which is a distributed watershed model was applied to analyze the spatial distribution of surface runoff and nonpoint source pollutant loading from Imha watershed during 2001~2010. L-THIA CN Calibration Tool linked with SCE-UA was developed to calibrate surface runoff automatically. Calibration (2001~2005) and validation (2006~2010) of monthly surface runoff were represented as 'very good' model performance showing 0.91 for calibration and 0.89 for validation as Nash-Sutcliffe (NS) values. Average annual surface runoff from Imha watershed was 218.4 mm and Banbyun subwatershed was much more than other watersheds due to poor hydrologic condition. Average annual nonpoint source pollutant loading from Imha wateshed were 2,295 ton/year for $BOD_5$, 14,752 ton/year for SS, 358 ton/year for T-N, and 79 ton/year for T-P. Amount of pollutant loading and pollutant loading rates from Banbyun watershed were much higher than other watersheds. As results of analysis of loading rate from grid size ($30m{\times}30m$), most of high 10 % of loading rate were generated from upland. Therefore, major hot spot area to manage nonpoint source pollution in Imha watershed is the combination of upland and Banbyun subwatershed. L-THIA model is easy to use and prepare input file and useful tool to manage nonpoint source pollution at screening level.

Development of Fishway Assessment Model based on the Fishway Structure, Hydrology and Biological Characteristics in Lotic Ecosystem

  • Choi, Ji-Woong;Park, Chan-Seo;An, Kwang-Guk
    • Journal of Ecology and Environment
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    • v.39 no.1
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    • pp.71-80
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    • 2016
  • The main goal of this study is to develop a multi-metric fishway assessment model (Mm-FA) and evaluate the efficiency of fishway. The Mm-FA model has three major fishway components with nine metrics: structural characteristics, hydraulic/hydrologic features, and biological attributes. The model was developed for diagnosing and assessing fishway efficiency and tested to Juksan Weir at the Yeongsan River Watershed. Structural characteristics of fishway included slope of the fishway (M1), ratios of fishway width to stream width (M2), and the proportion of orifice clogging and orifice size (M3). Hydraulic/hydrologic characteristics included depth of fishway entrance head (M4), depth of exit tail (M5), and current velocity of inner fishway (M6). Biological characteristics included fish species ratio of inner fishway to upper-lower weir (M7), fish length distribution (M8), and the proportion of migratory fish species to the total number of species (M9). Overall, the assessment of fishway efficiency showed the total score of the Mm-FA model was 25 in the Juksan Weir, indicating "good condition" by the criteria of the five-level classification system. The Mm-FA model may be used as a key tool for the assessment of fishway efficiency, especially on the 16 weirs constructed for the "Four Rivers Restoration Project" after a partial calibration of Mm-FA model.

An Analysis on the Stage-Discharge Relation Curve with the Temporal Variation of the River Bed -at Indogyo Station of the Han River- (하상(河床) 경년변화(經年變化)에 따른 수위(水位)-유량(流量) 관계곡선(關係曲線)의 해석(解析) -한강(漢江) 인도교지점(人道橋地點)을 중심(中心)으로-)

  • Cheong, Heung Soo;Lee, Won Hwan;Lee, Jae Joon
    • Journal of The Korean Society of Civil Engineers
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    • v.8 no.3
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    • pp.61-71
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    • 1988
  • The stage-discharge relation curve(rating curve) is the basic formula in hydrologic analysis. It plays an important role in converting to the discharge from available flood water level data including the daily mean stage. However, the river induces a cross section change at the gauging station because of the composed material of the river bed and three processes of the stream flow; i.e., erosion, transportation, and sedimentation. Rating curve has to be revised according to the temporal variation of the river bed due to the those factors. In this study, the basic rating curve is developed with respect to the current river bed to convert the existing rating curves and also to seize the hydraulic and geometric characteristics for the temporal variation of the river bed, relationships among the basic rating curve and the existing rating curves, water level, cross sectional area, and flow velocity are analyzed. Indogyo station, which is not only the key station of the Han river but also greatly changed the river bed after completion of the Han river development plan during the year 1983 to 1986, was chosen for the study. In this study, the river bed is assumed in a dynamic equilibrium condition. The basic rating curve is developed using hydrologic data of the physical year of 1987. For a given discharge, relationships for conversion of previous data, stage and velocity, the current one are formulated. To verify the usefulness of the relationships, stage-cross sectional area and stage velocity formula are also derived. Both hydrologic method using continuity equation and statistical method by the rating curve are compared and checked, then the validation of the both are positively shown.

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The Study on Development and Verification of Rainfall-Runoff Simulator for LID Technology Verification (LID 기술의 효율성 검증을 위한 강우-유출 모의장치 개발 및 검증실험에 관한 연구)

  • Jang, Young Su;Kim, Mi Eun;Baek, Jong Seok;Shin, Hyun Suk
    • Journal of Korea Water Resources Association
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    • v.47 no.6
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    • pp.513-522
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    • 2014
  • Climate change and urbanization have affected a increase of peak discharge and water pollution etc. In a view of these aspects, the LID(Low Impact Development) technology has been highlighted as one of adjustable control measures to mimic predevelopment hydrologic condition. Many LID technologies have developed, but there is a lack of studies with verification of LID technology efficiency. Therefore this study developed a rainfall-runoff simulator could be possible to verify LID technology efficiency. Using this simulator, this study has experimented the rainfall verification through the rainfall distribution experiment and the experiment to show the relation between inflow and effective rainfall in order to sprinkle the equal rainfall in each unit bed. As a result, the study defined the relation between allowable discharge range and RPM by nozzle types and verified the hydrologic cycle such as the relation between infiltration rate, surface runoff and subsurface runoff at pervious area and impervious area through the rainfall-runoff experiment.

Evaluation of Flood Control Capacity for Seongju Dam against Extreme Floods (이상강우에 대비한 성주댐의 홍수조절 능력 분석)

  • 권순국;한건연;서승덕;최혁준
    • Magazine of the Korean Society of Agricultural Engineers
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    • v.45 no.6
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    • pp.109-118
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    • 2003
  • As a fundamental research to establish a safety operation plan for irrigation dams, this study presents hydrologic analysis conducted in Sungju Dam watershed based on various rainfall data. Especially those reservoirs without flood control feature are widely exposed to the risk of flooding, a safe and optimized operation program need to be improved against arbitrary flooding. In this study, reservoir routing program was developed and simulated for reservoir runoff estimation using WMS hydrology model. The model simulated the variations of reservoir elevation under the condition of open or closed emergency gate. In case of closed emergency gate, water surface elevation was given as 193.15 m, and this value exceeds the dam crest height by 1.65 m. When the emergency gate is open, the increment of water surface elevation is given as 192.01 m, and this value exceeds dam crest height by 0.57 m. As an alternative plan, dam height increase can be considered for flood control under the PMP (Probable Maximum Precipitation) condition. Since the dam size is relatively small compare to the watershed area, sound protection can be expected from the latter option rather than emergency gate installation.

Estimation of Runoff Depth and Peak Discharge by SCS Curve Numbers and Time Variation of curve Numbers (SCS곡선번호에 의한 유출고 및 첨두유량의 산정과 곡선번호의 시변성)

  • 윤태훈
    • Water for future
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    • v.25 no.4
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    • pp.87-95
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    • 1992
  • The validity of the estimate of runoff depth and peak runoff by the basin runoff curve numbers(CN-II for AMC-II condition and CN-III for AMC-III condition) obtained from hydrologic soil-cover complexs is investigated by making use of the observed curve numbers(median curve number and optimum curve number) computed from rainfall-runoff records. For gaged basins the median curve numbers are recommended for the estimation of runoff depth and peak runoff. For ungaged basins, found is that for the estimate of runoff depth CN-III is adequate and for the peak runoff CN-II is adequate. Also investigated is the variation of curve numbers during rainfall, which is turned out to improve the estimates of both depth and peak of runoff.

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Hydrologic Performance Characteristics of Small Hydropower Resources with Rainfall Condition (강우상태에 따른 소수력자원의 수문학적 특성 분석)

  • Lee, Chulhyung;Park, Wansoon
    • 한국신재생에너지학회:학술대회논문집
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    • pp.207.2-207.2
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    • 2011
  • 소수력자원의 개발을 위해서는 소수력발전입지에 대한 설계변수의 분석이 매우 중요하다. 설계변수는 해당유역의 강우사상과 밀접한 관계가 있으므로 이에 대한 정량적인 분석이 요구된다. 본 연구에서는 수계별 소수력발전입지에 대하여 설계변수의 특성을 분석하였다. 분석결과, 금강수계, 남한강수계 및 섬진강수계는 유역면적이 증가하여도 비가용량의 변화가 크지않지만, 낙동강수계와 북한강수계는 유역면적의 크기에 관계없이 비가용량의 변화가 크게 나타났다. 또한 비출력량의 경우에도 비가용량과 유사하게 금강수계, 남한강수계 및 섬진강수계는 유역면적이 증가하여도 비출력량의 변화가 크지않지만, 낙동강수계와 북한강수계는 유역면적의 크기에 관계없이 비출력량의 변화가 크게 나타났다. 이러한 현상은 우리나라의 연강수량이 남부지방이 중부지방에 비하여 많기 때문으로 판단된다. 낙동강수계는 하도가 남북으로 길기 때문에 소수력발전입지의 위치에 따라 비가용량의 크기의 변화가 크고, 북한강수계도 이와 비슷한 경향을 갖는다. 반면에 금강수계, 남한강수계 및 섬진강수계는 하도가 동서방향으로 길기 때문이다. 또한 연간가동율의 경우에는 모든 수계에 대하여 변화가 크지 않았고, 유역면적의 변화에 대해서도 큰 변화가 없었다.

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