• Journal of Environmental Science International
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• v.18 no.9
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• pp.971-981
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• 2009

An objective of this study is as follows: 1) performing sensitivity analysis and parameter estimation of RMA2 and RMA4 models for the West-Nakdong River, 2) drawing up alternatives of gates-operation for water-quality enhancement, and 3) quantitative evaluation of methodology of 'flow-restoration by gates-operation' among 'Comprehensive Plan Improving Water-Quality in the West-Nakdong River(WNR)' with the target water-quality(BOD at Nakbon-N point: below 4.3 mg/L). The parameters for the RMA2 (depth-averaged two-dimensional flow model) and RMA4 (depth-averaged two-dimensional water-quality model) were determined by sensitivity analysis. Result of parameter estimation for RMA2 and RMA4 models is $1,000\;Pa{\cdot}s$ of the eddy viscosity, 20 of the Peclet number, 0.025 of the Manning coefficient, and $1.0\;m^2/s$ of the diffusion coefficient. We have evaluated the effects of water-quality enhancement of the selected alternatives by numerical simulation technique with the models under the steady-state flow condition and the time-variant transport condition. Because of no-resuspension from river bottom and considering BOD as conservative matter, these simulation results slightly differ from real phenomena. In the case of $50\;m^3/s$ of Daejeo-gate inflow, two-dimensional flow pn results result represents that small velocity occurs in the Pyungkang Stream and no flow in the Maekdo River. In the WNR, there occurs the most rapid flow near timhae-bridge. In the WNR, changes of water-quality for the four selected simulation cases(6, 10, 30, $50\;m^3/s$ of the Daejeo-gate inflow) were predicted. Since the Daejeo-Gate and the Noksan-Gate can be opened up to 7 days, it would be found that sustainable inflow of $30\;m^3/s$ at the Daejeo-gate makes BOD in the WNR to be under the target of water-quality.

• Journal of Environmental Science International
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• v.11 no.12
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• pp.1205-1215
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• 2002

To evaluate the change for water quality after the water gate operation in Shiwha lake, in situ survey were conducted on september in 2000 and January, march, jane in 2001. Chemical characteristics and eutrophication level was estimated from the survey data. The water quality of the Shihwa lake was greatly affected by pollutant load from rainfall, and formation of stratification in summer and winter was increased to effect on nutrient release from sediment. Especially, high concentration of chlorophyll-a was occurred in autumn, due to increased nutrient, high water temperature and low salinity after rainfall runoff. The mean concentration of DIN, DIP were 0.346mg/L, 0.0217mg/L in surface water and 0.826mg/L, 0.0415mg/L in bottom water, respectively, which were over III grade of seawater standard. Also high percentage of ammonia nitrogen to DIN in bottom water for autumn and winter was affected by released nutrient from sediment. Correlation analysis of chlorophyll-a versus TSS was shown that organic matter was affected by autochthonous organic matter stem from the algae, these factor showed reverse correlation about salinity. Closely correlations among to the water quality constituent in continuity survey was appeared. The results of eutrophication index estimation showed the high potentiality of red tide occurrence in Shiwha lake, particularity in summer or fall. Overall water quality was greatly improve to compared with measuring data during 1997~1998 at the beginning water gate operation, which reported by KORDI. Therefore, to improve of water quality in Shiwha lake, we need to establish of management plan about nutrient release from sediment, rainfall runoff, maximum of seawater exchange.

• Journal of Korea Water Resources Association
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• v.45 no.7
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• pp.675-684
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• 2012

Recently, a heavy rainfall under climate change causes the flood exceeded river's conveyance. Flood control methods under the limited river width are the increase of embankment, the construction of storage pockets and diversion channel, the dredging of river bed. Hwasun flood control reservoir of washland is designed as the storage pockets and the regulating gate for the control of water level. In this study, the propriety of design was investigated through hydraulic experiments for the circumstances to exclude the constant flood discharge during operation period. In the results, the over flow rate of side weir exceeded the flow of design and indicated to be able to discharge the designed flow in the regulating gate opened 1.1 m. The high velocity 7.1 m/s behind the gate has investigated to reduce under 3.3 m/s by the baffle block.

• Water for future
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• v.22 no.1
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• pp.91-98
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• 1989

This study was aimed to determine a discharge coefficient of flow through gate piers. The coefficient was Calbrated with water stage data observed during 1984 to 1987 at the Young San Estuary Dam. The coefficient is the function of the dimensionless parameters combined with the difference between up and down stream water level to down stream water depth ratio and water surface draw down ratio. From the verification with existing methods and actual drainages, drainages predicted by the relationship have the most consistency with the actual drainages, also Matthai's method can be used within the proposed condition originally.

• Magazine of the Korean Society of Agricultural Engineers
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• v.37 no.2
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• pp.13.2-20
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• 1995

An water balance model was formulated to simulate the change in water levels at the estuary reservoir from sluice gate releases and the inflow hydrographs, and an one-di- mensional flood routing model was formulated to simulate temporal and spatial varia- tions of flood hydrographs along the estuarine river. Flow rates through sluice gates were calibrated with data from the estuary dam, and the results were used for a water balance model, which did a good job in predicting the water level fluctuations. The flood routing model which used the results from two hydrologic models and the water balance model simulated hydrographs that were in close agreement with the observed data. The flood forecasting model was found to be applicable to real-time forecasting of water level fluc- tuations with reasonable accuracies.

• The Journal of the Korea institute of electronic communication sciences
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• v.5 no.5
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• pp.504-508
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• 2010

A reducing labor is a big issue in rural community due to a increasingly aging society. In this paper, the water control system for corps production with a function of automatically controls and solar energy system is developed. The water level was measured by ultrasonic sensor and water gate was controlled by using servo motor. The system had included ATmega 128 control unit for signal controls. The water level control system will be able to contribute to the aging rural society.

• Journal of The Korean Society of Agricultural Engineers
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• v.58 no.6
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• pp.31-38
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• 2016

The purpose of this study was to assess nonpoint sources (NPS) pollution affected by liquid manure and regulating gate in a small agricultural watershed. The study area, which is a wide plain farmland, was operating by the Buyong regulating gate in order to maintain irrigation water level during irrigation period. Consequentially, runoff only occurs through the gate at each event in rainy season for avoiding farmland inundation. In addition, the usage ratio of liquid manure in the study area has been increased greatly since 2014. Discharge loads at the Hwaingsan bridge subwatershed were 1.2 times for T-N, 4-10 times for T-P, and 3-8 times for TOC compared with the Soyang watershed (control) during study period. The reason was that NPS pollutants from upper Gpeun and Sangri bridge subwatersheds, which are widely spraying with livestock liquid manure, were stack at this subwaterehd because of regulating gate in non-rainy seasons. A number of agricultural watersheds in Saemangeum watershed are affected by regulating gate and vigorous livestock activities so that substantial management schemes under controling regulating gate are needed for minimizing livestock related NPS.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2005.10a
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• pp.306-312
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• 2005

Gates for the purpose of drainage are classified following the types of structure as: Radial Gate, Sluice Gate, Rolling Gate, Drum Gate. In many cases of the reclamation project the sluice type of gates are applied. Different from this general trend, however the radial type of gate was adopted in the Saemangeum project. In this case the discharge coefficients which are used for the sluice type of gate was applied. To estimate the correct amount of discharge which will be evacuated through the gates, therefore the proper discharge coefficients should be estimated before the operation of the gates. The discharge coefficients were estimated through the physical hydraulic modeling, and we got the results as: $0.72{\sim}0.84$ for the submerged condition on the both sides of upstream and downstream, $0.62{\sim}0.83$ for the free surface condition on the downtream side only, and $1.04{\sim}1.12$ for the free surface condition on the both sides of upstream and downstream. The discharge coefficients obtained from the experiments are greater than those of the sluice gates in the design criteria. From the results of the study we may expect that in the Saemangeum project the radial gates could evacuate larger amount of discharge than the originally designed discharge, so that we may sure that the Saemangeum gates have enough capability to control the evacuation of water not only in the usual period but also in the flooding season.

• Structural Engineering and Mechanics
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• v.17 no.5
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• pp.611-626
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• 2004

On the basis of a structural analysis of radial gate (i.e. Tainter gate), the current paper focuses on weight minimization according to the location of the arms on a radial gate. In spite of its economical significance, there are hardly any previous studies on the optimum design of radial gate. Accordingly, the present study identifies the optimum position of the support point for a radial gate that guarantees the minimum weight satisfying the strength constraint conditions. This study also identifies the optimum position for 2 or 3 radial arms with a convex cylindrical skin plate relative to a given radius of the skin plate curvature, pivot point, water depth, ice pressure, etc. These optimum designs are then compared with previously constructed radial gates. Local genetic and hybrid-type genetic algorithms are used as the optimum tools to reduce the computing time and enhance the accuracy. The results indicate that the weights of the optimized radial gates are appreciably lower than those of previously constructed gates.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.22 no.4
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• pp.258-271
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• 2010

In order to figure out hydrodynamic and water quality changes after completion of dike construction of the Saemangeum, which behaves as a semi-enclosed estuarine lake, numerical simulations based on fine grid structure by using EFDC were intensively carried out. In this study some limitations of precedent study has been improved and gate operation were considered. Also 3 phases such as air-water-sediment interaction modeling was considered. It is clear that inner mixing of the Saemangeum is dominated by Mankyeong and Dongjin riverine discharges rather than the gate opening influence through the Lagrangian particle tracking simulations. Vertical DO structure after the dike completion shows steep gradient especially at Dongjin river estuary due to lessen of outer sea water exchange. Increasing SOD at stagnantly changed man-made reservoir might cause oxygen deficiency and accelerating degradation of water quality. According to TSI evaluation test representing eutrophication status, it shows high possibility of eutrophication along Mankyeong waterway in spite of dike completion, while the index is getting high after final closing along Dongjin waterway. Numerical tests with gate operations show significant differences in water quality. Thus it should be noted that proper gate operation plays a major role in preserving target water quality and management for inner development plan.