• Title/Summary/Keyword: selective withdrawal

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Assessment of Selective Withdrawal Facility in the Imha Reservoir Using CE-QUAL-W2 Model (CE-QUAL-W2 모델을 이용한 임하호 선택배제시설의 효과분석)

  • Lee, Sanguk;Kim, Jeongkon;Noh, Joonwoo;Ko, Ick Hwan
    • Journal of Korean Society on Water Environment
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    • v.23 no.2
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    • pp.228-235
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    • 2007
  • For efficient turbid water withdrawal in the Imha reservoir, a selective withdrawal facility was recently installed and operated during summer season of year 2006. In this research, CE-QUAL-W2 model was utilized to assess the efficiency of the selective withdrawal facility, in comparison with the original surface withdrawal, on turbid water management. Model calibration was carried out using data observed at four automatic monitoring stations in the reservoir. It was found that the model appropriately simulated, with the RMSE less than 5.2 NTU, the observed vertical and horizontal distributions of water temperature and turbidity as well as the location of maximum turbid water at each monitoring station. The analysis results showed that selective withdrawal is more effective in removing high turbid water than surface withdrawal as selective withdrawal contributed to reducing $35Mm^3$ of high turbidity water (> 100 NTU) in the reservoir by increasing outflows of high turbid water. Therefore, effective management of turbid water in the reservoir can be achieved by changing locations of intake depending on turbid water distribution conditions. The results of this study will provide some basic information for establishing better operation strategies to cope with turbid water problems.

Inflow Patterns Around a Water Intake Tower for Selective Withdrawal Depth (선택취수 수심에 따른 취수탑 유입유동 특성)

  • Cho, Yong;Kim, Yong-Yeol
    • The KSFM Journal of Fluid Machinery
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    • v.13 no.6
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    • pp.63-70
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    • 2010
  • Shallow water withdrawal systems have been replaced with a selected withdrawal system to keep stable raw water quality in spite of occurrence of algae and muddy inflow. Before reconstruction of the water intake tower in Yongdam reservoir supplying water to Gosan water treatment facility, we have predicted flow patterns of inflowing water into the water intake tower for various withdrawal conditions. It has been predicted that the water in the withdrawal layer is significantly inflowed from the front with fast velocity into the water intake tower irrespective of withdrawal depth, while the water away from the withdrawal layer is withdrawed a little from the side with slow velocity.

Experimental Study on the Velocity Structure of 2-D Density Current Induced by Selective Withdrawal (선택취수에 의한 2차원 밀도류의 흐름특성에 관한 실험적 연구)

  • Lyu, Siwan;Kim, Young Do;Cho, Gilje;Kwon, Jae Hyun;Lee, Nam Joo
    • Journal of Korean Society of Water and Wastewater
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    • v.23 no.6
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    • pp.825-832
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    • 2009
  • A series of laboratory experiments has been performed to investigate the flow characteristics of 2-dimensional density currents induced by selective withdrawal, which is commonly suggested as a measure for removal of high turbid water from reservoirs. Saltwater has been used to simulate the density stratification over depth and PIV(Particel Image Velocimetry) for observing the velocity structure. Experimental conditions have been established according to Richardson number, which is the dimensionless number that expresses the ratio of potential to kinetic energy. From the experiments, the patterns of longitudinal decay of centerline axial velocity induced by the withdrawal have been distinguished from other experimental cases. The rate of longitudinal decay increase as the Richardson number increases. The variations of volumetric and momentum flux along the longitudinal axis have also shown to be dependent on Richardson number.

Effect of Selective Withdrawal on the Control of Turbidity Flow and Its Water Quality Impact in Deacheong Reservoir (선택취수에 따른 대청호 탁수 조절효과 및 수질영향 분석)

  • Jung, Yong-Rak;Liu, Huan;Kim, Yu-Kyung;Ye, Lyeong;Chung, Se-Woong
    • Journal of Korea Water Resources Association
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    • v.40 no.8
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    • pp.601-615
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    • 2007
  • A selective withdrawal method has been widely used to control the quality of water released from a stratified reservoir and to improve downstream ecosystem habitats. Recently, several existing reservoir withdrawal facilities have been modified to accommodate multi-level water intake capabilities in order to adapt the impact of long-term discharge of high turbidity flow. The purpose of this study was to assess the effect of selective withdrawal method on the control of downstream turbidity and its impact on water quality in Daecheong Reservoir. A laterally integrated two-dimensional hydrodynamic and eutrophication model, which was calibrated and validated in the previous studies, was applied to simulate the temporal variations of outflow turbidity with various hypothetical selective withdrawal scenarios. In addition, their impacts on the algal growth as well as water quality constituents were analyzed in three different spatial domains of the reservoir The results showed that the costly selective withdrawal method would provide very limited benefits for downstream turbidity control during two years of consecutive simulations for 2004-2005. In particular, an excessive withdrawal from the epilimnion zone for supplying upper layer clean water resulted in movement of turbidity plume that contained high phosphorus concentrations upward photic zone, and in turn increased algal growth in the lacustrine zone.

A Study on Field Experiment and Numerical Modeling for Efficiency Analysis of Selective Withdrawal in Imha Reservoir (임하호 선택취수 효과분석을 위한 현장실험 및 수치해석 연구)

  • Kim, Tae Won;Kim, Young Do;Yi, Yong-Kon
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.32 no.2B
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    • pp.113-121
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    • 2012
  • When a heavy rain brings flooding, a high turbid water is flowing into a reservoir. In this study, the effectiveness of the intake structures for the selective withdrawal from the various levels of a stratified reservoir was evaluated by the field experiments and the numerical modeling of the three-dimensional approaching flows. The temperature, the turbidity, and the velocity fields for the selective withdrawal were measured using both YSI6600EDS and YSI6600ADV, respectively. A threedimensional model, FLOW-3D, was used to predict the performance of the intake tower in Imha reservoir. The comparisons of the vertical velocity field showed a good agreement with the field measurements. The efficiency of the turbid-water elimination of the selective withdrawal method from low levels was higher up to 46% than that of the surface withdrawal. From the analysis of the numerical simulation, the efficiency of turbidity elimination increased by 10% for the selective withdrawal from middle levels, and by 30% from low levels. These results showed that the selective withdrawals from middle and low levels are more effective than the surface-water intake. The similar results were obtained by the one-dimensional model, SELECT, which is much more computationally time-efficient.

Numerical Simulation of Selective Withdrawal in Stably Stratified Flows (안정성층류에서 선택취수의 수치해석)

  • Paik, Joong-Cheol
    • Journal of Korea Water Resources Association
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    • v.38 no.11
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    • pp.973-984
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    • 2005
  • A three-dimensional thermal hydrodynamic model is developed for carrying out unsteady simulation of the selective withdrawal of the stably stratified flow in a geometrically complex, natural reservoir The governing equations are discretized on a non-staggered grid using a second-order accurate, finite-volume scheme. The numerical model is validated by applying it to simulate three-dimensional, turbulent, stratified, shear-layer flow case. The numerical predictions appear to capture reasonably well the general shape of velocity and temperature profiles observed in the laboratory experiments, while significant overestimation of the magnitude of velocity profiles is observed in the application to the flow in a natural reservoir. The physics of selective withdrawal as emerge from the numerical simulations are also discussed.

An Experimental Study on Selective Withdrawal from Linear Stratified Tank (선형 성층수조에서의 선택취수에 관한 실험적 연구)

  • Kim, Young Do;Park, Jae Hyeon;Son, Byung Ju
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.31 no.6B
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    • pp.499-505
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    • 2011
  • The mixing behavior of turbidity currents in a reservoir is closely related with the annual temperature change of the reservoir. In the summer, the reservoir has a well defined structure: one or two thermoclines and some layers of different densities. This density stratification inhibits vertical mixing and affects various hydrodynamic processes within the reservoir. Therefore, many reservoirs can be operated to release water of the specific quality with the selective withdrawal. In this study, the hydraulic experiments were performed to analyze the efficiency of selective withdrawal. The velocity distributions are measured with PIV in the stratified tank with the "two-tank" method. The relationship between the Richardson number and the selective withdrawal efficiency are provided using the measured velocity distributions.

Effect on Phytoplankton by Hydraulic-Gun-Aerators and Selective Withdrawal in Hoengseung Reservoir (횡성호 식물플랑크톤에 대한 간헐식 폭기의 영향과 선택취수)

  • Choi, Il-Hwan;Kim, Hak-Chul
    • Journal of Environmental Impact Assessment
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    • v.16 no.1
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    • pp.15-26
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    • 2007
  • Surface water is the main drinking water source in Korea. Algal bloom caused by phytoplankton in reservoir is common event in every summer season. To prevent or control the algal blooms, artificial circulation system has been adopted in many reservoirs, including Hoengseung reservoir. Total 7 hydraulic-gun-aerators were installed around the intake tower in Hoengseung reservoir since 2000. This study is to elucidate the effects of hydraulic-gun-aerators on phytoplankton bloom, pH, DO, temperature and evaluate the selective withdrawal and vertical distribution of phytoplankton by means of submersible fluorescence probe, which features high correlation with a standard ISO method (r=0.90, P<0.0001) for chlorophyll-a quantification.

Development of a Decision Support System for Turbid Water Management through Joint Dam Operation

  • Kim, Jeong-Kon;Ko, Ick-Hwan;Yoo, Yang-Soo
    • Proceedings of the Korea Water Resources Association Conference
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    • 2007.05a
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    • pp.31-39
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    • 2007
  • In this study we developed a turbidity management system to support the operation for effective turbid water management. The decision-making system includes various models for prediction of turbid water inflow, effective reservoir operation using the selective withdrawal facility, analysis of turbid water discharge in the downstream. The system is supported by the intensive monitoring devices installed in the upstream rivers, reservoirs, and downstream rivers. SWAT and HSPF models were constructed to predict turbid water flows in the Imha and Andong catchments. CE-QUAL-W2 models were constructed for turbid water behavior prediction, and various analyses were conducted to examine the effects of the selective withdrawal operation for efficient high turbid water discharge, turbid water distribution under differing amount and locations of turbid water discharge. A 1-dimensional dynamic water quality model was built using Ko-Riv1 for simulation of turbidity propagation in the downstream of the reservoirs, and 2-dimensional models were developed to investigate the mixing phenomena of two waters discharged from the Andong and Imha reservoirs with different temperature and turbidity conditions during joint dam operation for reducing the impacts of turbid water.

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Evaluation of SELECT Model for the Quality Prediction of Water Released from Stratified Reservoir (성층화된 저수지의 방류수 수질예측을 위한 SELECT 모델의 적용성 검토)

  • Lee, Heung Soo;Chung, Se Woong;Shin, Sang Il;Choi, Jung Kyu;Kim, Yu Kyung
    • Journal of Korean Society on Water Environment
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    • v.23 no.5
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    • pp.591-599
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    • 2007
  • The quality of water released from a stratified reservoir is dependent on various factors such as the location and shape of intake facility, structure of reservoir stratification, profile of water quality constituent, and withdrawal flux. Sometimes, selective withdrawal capabilities can provide the operational flexibility to meet the water quality demands both in-reservoir and downstream. The objective of this study was to evaluate the performance of a one-dimensional reservoir selective withdrawal model (SELECT) as a tool for supporting downstream water quality management for Daecheong and Imha reservoirs. The simulated water quality variables including water temperature, dissolved oxygen (DO), conductivity, turbidity were compared with the field data measured in tailwater. The model showed fairly satisfactory results and high reliability in simulating observations. The coefficients of determinant between simulated and observed turbidity values were 0.93 and 0.95 for Daecheong and Imha reservoirs, respectively. The outflow water quality was significantly influenced by water intake level under fully stratified condition, while the effect of intake amount was minor. In conclusion, the SELECT is simple but effective tool for supporting downstream water quality prediction and management for both reservoirs.