• Title/Summary/Keyword: flow duration

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Evaluating Calibration Methods of Stream Flow for Water Quality Management (수질학적 관점에서의 수문모델 유출량 보정 방법 평가)

  • Jeon, Ji-Hong;Choi, Donghyuk;Kim, Jung-Jin;Kim, Taedong
    • Journal of Korean Society on Water Environment
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    • v.25 no.3
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    • pp.432-440
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    • 2009
  • The effect of selecting hydrologic item for calculating objective function on calibration of stream flow was evaluated by Hydrologic Simulation Porgram-Fortran (HSPF) linked with Model Independent Parameter Optimizer (PEST). Daily and monthly stream flow and flow duration were used to calculate objective function. Automated calibration focused on monthly stream was proper to analyze seasonal or yearly water budget but not proper to predict daily stream flow or percent chance flow exceeded. Calibration result focused on flow duration is proper to predict precent chance flow exceeded but not proper to analyze water budget or predict peak flow. These results indicate that hydrologic item calculated for objective function on calibration procedure could influence calibration results and watershed modeler should select carefully hydrologic item for the purpose of model application. Current, the criteria of stream flow of Korean TMDL is generated based on percent chance flow exceeded, so flow duration should be included to calculate objective function on calibration procedure for the estimation of criteria of stream flow using hydrologic model.

Proposal and Application of Water Deficit-Duration-Frequency Curve using Threshold Level Method (임계수준 방법을 이용한 물 부족량-지속기간-빈도 곡선의 제안 및 적용)

  • Sung, Jang Hyun;Chung, Eun-Sung
    • Journal of Korea Water Resources Association
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    • v.47 no.11
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    • pp.997-1005
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    • 2014
  • This study evaluated hydrological drought the using the annual minimum flow and the annual maximum deficit method and proposed the new concept of water deficit-duration-frequency curves similar to rainfall intensity-duration-frequency curves. The analysis results of the annual minimum flow, the return periods of hydrological drought in the most duration of 1989 and 1996yr were the longest. The analysis results of the annual maximum deficit, the return periods of 60-days and 90-day deficit which are relatively short duration were the longest in 1995yr, about 35-year, Hydrological drought lasted longer was in 1995, the return period was about 20-year. Though duration as well as magnitude is a key variable in drought analysis, it was found that the method using the annual minimum flow duration not distinguish duration.

A Study on Estimation of Factors Affecting Duration of Milk Flow and Milk Flow Rate and Their Relationships with Milk Yields of Dairy Cattle (유우의 착유 지속시간과 유속에 미치는 요인 및 산유량과의 상관관계 추정에 관한 연구)

  • Cho, Y.M.;Park, B.H.;Ahn, B.S.
    • Journal of Animal Science and Technology
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    • v.46 no.4
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    • pp.517-524
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    • 2004
  • The objective of this study was to investigate the environmental effects on duration time of milk flow, peak milk flow, and average milk flow in teats, and to estimate their relationships with milk yields in morning and evening milking, and to provide fimdamental information for the further study on their relationships with clinical mastitis and somatic cell in milk. A total of 6,768 milking records were studied in 72 Holstein cows. The influences of season, parity, lactation month, and milking interval on characteristics of milk flow considering in linear model were significant(p<.05). Duration of milk flow was longest at milking in fall, past first parity and second month of lactation, and with milking interval over than 13.5hrs. Average milk flow rate and peak milk flow rate were highest at milking in summer, past first parity and 8${\sim}$10 months of lactation, and with milking interval over than 13.5hrs. Milk flow rate was positively correlated to milk yield, and negatively correlated to the duration of milk flow. However duration milk flow was positively correlated to the milk yield with high level of correlation coefficient(+.60). For the establishment of optimum selection criteria on these traits, other aspects such as the udder health, disease and respective economic weights of milk flow characteristics in this study must be considered to develop the indices.

Development of Long Term Flow Duration Curves in 4 River Basins for the Management of Total Maximum Daily Loads (수질오염총량관리를 위한 4대강수계 장기유황곡선 작성방안)

  • Park, Jun Dae;Oh, Seung Young
    • Journal of Korean Society on Water Environment
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    • v.29 no.3
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    • pp.343-353
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    • 2013
  • Flow duration curve (FDC) can be developed by linking the daily flow data of stream flow monitoring network to 8-day interval flow data of the unit watersheds for the management of Total Maximum Daily Loads. This study investigated the applicable method for the development of long term FDC with the selection of the stream flow reference sites, and suggested the development of the FDC in 4 river basins. Out of 142 unit watersheds in 4 river basins, 107 unit watersheds were shown to estimate daily flow data for the unit watersheds from 2006 to 2010. Short term FDC could be developed in 64 unit watersheds (45%) and long term FDC in 43 unit watersheds (30%), while other 35 unit watersheds (25%) were revealed to have difficulties in the development of FDC itself. Limits in the development of the long term FDC includes no stream monitoring sites in certain unit watersheds, short duration of stream flow data set and missing data by abnormal water level measurements on the stream flow monitoring sites. To improve these limits, it is necessary to install new monitoring sites in the required areas, to keep up continuous monitoring and make normal water level observations on the stream flow monitoring sites, and to build up a special management system to enhance data reliability. The development of long term FDC for the unit watersheds can be established appropriately with the normal and durable measurement on the selected reference sites in the stream flow monitoring network.

Determining the flow curves for an inverse ferrofluid

  • Ekwebelam, C.C.;See, H.
    • Korea-Australia Rheology Journal
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    • v.20 no.1
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    • pp.35-42
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    • 2008
  • An inverse ferrofluid composed of micron sized polymethylmethacrylate particles dispersed in ferrofluid was used to investigate the effects of test duration times on determining the flow curves of these materials under constant magnetic field. The results showed that flow curves determined using low duration times were most likely not measuring the steady state rheological response. However, at longer duration times, which are expected to correspond more to steady state behaviour, we noticed the occurrence of plateau and decreasing flow curves in the shear rate range of $0.004\;s^{-1}$ to ${\sim}20\;s^{-1}$, which suggest the presence of nonhomogeneities and shear localization in the material. This behaviour was also reflected in the steady state results from shear start up tests performed over the same range of shear rates. The results indicate that care is required when interpreting flow curves obtained for inverse ferrofluids.

A Study on the Estimation of River Management Flow in Urban Basin (도시유역의 하천유지용수 산정에 관한 연구)

  • 이영화
    • Journal of Environmental Science International
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    • v.5 no.3
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    • pp.377-385
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    • 1996
  • This study aims at the estimation of a river management flow in urban basin analyzing Sinchun basin to be the tributary of Kumho river basin. The river management flow has to satisfy a low flow as natural flow and an environmental preservation flow estimated by a dilution flow to satisfy a target water quality in drought flow. Therefore for the estimation of a river management flow in Sinchun in this study, first Tank model as a basin runoff model estimates a low flow, a drought flow from a flow duration curve in Sinchun, second QUAL2E model as water quality model simulates water quality in Sinchun and estimates environmental preservation flow to satisfy a target water qua%its, BOD 8 mg/l by a dilution flow derived from Kumho river, Nakdong river and around water. And the river management flow is estimated by addition of a use flow and a loss flow to more flow between a low-flow and an environmental preservation flow.

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A Study on Estimation of the Delivery Ratio by Flow Duration in a Small-Scale Test Bed for Managing TMDL in Nakdong River (낙동강수계 수질오염총량관리를 위한 시범소유역 유황별 유달율 산정방법 연구)

  • Shon, Tae-Seok;Park, Jae-Bum;Shin, Hyun-Suk
    • Journal of Korean Society on Water Environment
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    • v.25 no.5
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    • pp.792-802
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    • 2009
  • The objective of this study is to construct the watershed management system with link of the non-point sources model and to estimate delivery ratio duration curves for various pollutants. For the total water pollution load management system, non-point source model should be performed with the study of the characteristic about non-point sources and loadings of non-point source and the allotment of pollutant in each area. In this study, daily flow rates and delivered pollutant loads of Nakdong river basin are simulated with modified TANK model and minimum variance unbiased estimator and SWAT model. Based on the simulation results, flow duration curves, load duration curves, and delivery ratio duration curves have been established. Then GIS analysis is performed to obtain several hydrological geomorphic characteristics such as watershed area, stream length, watershed slope and runoff curve number. As a result, the SWAT simulation results show good agreements in terms of discharge, BOD, TN, TP but for more exact simulation should be kept studying about variables and parameters which are needed for simulation. And as a result of the characteristic discharges, pollutants loading with the runoff and delivery ratios, non-point sources effects were higher than point sources effects in the small-scale test bed of Nakdong river basin.

Approximation Method of Environmental Flows based on Flow Duration Curves (유황곡선을 기반으로 한 환경유량의 개략산정법)

  • Kim, Joo-Cheol;Lee, Sang-Jin;Ko, Ick-Hwan;Woo, Dong-Hyun
    • Proceedings of the Korea Water Resources Association Conference
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    • 2010.05a
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    • pp.933-937
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    • 2010
  • This study aimed at the introduction of desktop method for assessment of environmental flows developed by IWMI(International Water Management Institute) recently and its application to Geum river basin. This scheme simulated the influence on aquatic ecosystem caused by watershed development and in turn the decrease of water quantity keeping the river's own flow regime. It was found to be as very effective method although it had simple structure. Flow duration curves for different environmental classes at Sutong and Gongjoo sites were estimated according to the natural conditional scenario of Geum river basin and the results were relatively compared well with the previous studies. The behaviors of monthly average runoff time series of both sites showed the level of A class. The results of this study would provide the fundamental data to establish the future plans of monitoring or management for aquatic ecosystem of Geum river basin.

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Analysis of Flow Duration Based on SWAT-K Simulation for Construction of Natural Riparian (자연하안조성을 위한 SWAT-K 모의치 기반 유황 분석)

  • Kim, Nam-Won;Lee, Jeong-Woo;Chung, Il-Moon;Kim, Ji-Tae
    • Journal of Environmental Science International
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    • v.20 no.11
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    • pp.1457-1464
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    • 2011
  • In this study, the method of estimating hydrologic information (water depth, submerged period etc.) on the proper selection of construction point and scale as well as vegetation type suggested for the design of natural riparian rehabilitation structure. Long-term comprehensive watershed model SWAT-K(Korea) was applied to this purpose. Flow duration analysis was conducted to analyze the hydrologic characteristics of Pyungchang watershed at which the 'bangtul' construction method was tested. For this purpose 20 years (1989-2008) rainfall runoff analysis was carried out. Based on the simulated daily streamflow data, flow duration curve was made to analyze the flow characteristics, and the water depth hydrograph was made to analyze the water depth distribution at the cross section. Finally, the information for the selection of proper vegetation according to the submerged period is suggested.

Runoff Characteristics Analysis for Interior Drainage Systems in Urban Basin -Application of SWMM- (도시유역의 내수배제시스템 설계를 위한 유출특성분석 -SWMM의 적용-)

  • Choi, Yun-Young;Lee, Yeong-Hwa
    • Journal of Environmental Science International
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    • v.9 no.3
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    • pp.193-199
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    • 2000
  • This study is carried out the analysis of the runoff characteristics for the design of the interior drainage systems by SWMM in urbanization basin. The basin analyzed in this study is Bumuh-chun basin which is located in Susung-gu of Taegu city. Huff method is used for rainfall distribution analysis. The optimal rainfall duration in Bumuh-chun basin is analyzed as about 90 minutes decided from comparison of arrival time and critical duration. Flood flow variation pattern is proposed through the comparison of the results of peak flow and peak time analyzed by SWMM about pre-urbanization and post-urbanization of Bumuh-chun basin. It is known that the variation of arrival time caused by the rapid increase of pavement rate in the upper area shows about 20∼25 minutes faster than pre- urbanization. Therefore, the management of surface water for design of water supply and drainage, and channel alteration has to considered the variation of geological factors according to urbanization.

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