• Journal of Korea Water Resources Association
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• v.44 no.9
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• pp.741-751
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• 2011

In this study, a methodology was devised to overcome that difficulty for thermal stratification modeling using EFDC. For the increase of reproductability for thermal stratification analysis, the effect of parameter such as distribution of solar radiation, depth of active bed temperature layer, heat transfer coefficients were analyzed. The simulation period was from June to December in 2005 and statistical index is used to analyze the model results. The results showed that distribution of solar radiation is zero and depth of active bed temperature layer is 10 m are suitable for simulation of thermal stratification in Yongdam Dam reservoir. This study results can be used for guideline to analyze the thermal stratification of large dam reservoir in Korea.

• Advances in environmental research
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• v.5 no.3
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• pp.153-167
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• 2016

We applied multilayer perceptron (MLP) and radial basis function (RBF) neural network in upstream and downstream water quality stations of the Karaj Reservoir in Iran. For both neural networks, inputs were pH, turbidity, temperature, chlorophyll-a, biochemical oxygen demand (BOD) and nitrate, and the output was dissolved oxygen (DO). We used an MLP neural network with two hidden layers, for upstream station 15 and 33 neurons in the first and second layers respectively, and for the downstream station, 16 and 21 neurons in the first and second hidden layer were used which had minimum amount of errors. For learning process 6-fold cross validation were applied to avoid over fitting. The best results acquired from RBF model, in which the mean bias error (MBE) and root mean squared error (RMSE) were 0.063 and 0.10 for the upstream station. The MBE and RSME were 0.0126 and 0.099 for the downstream station. The coefficient of determination ($R^2$) between the observed data and the predicted data for upstream and downstream stations in the MLP was 0.801 and 0.904, respectively, and in the RBF network were 0.962 and 0.97, respectively. The MLP neural network had acceptable results; however, the results of RBF network were more accurate. A sensitivity analysis for the MLP neural network indicated that temperature was the first parameter, pH the second and nitrate was the last factor affecting the prediction of DO concentrations. The results proved the workability and accuracy of the RBF model in the prediction of the DO.

• Korean Journal of Ecology and Environment
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• v.35 no.3 s.99
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• pp.181-186
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• 2002

To evaluate the eutrophication status of the Asan Reservoir in Korea, physicochemical parameters were analyzed for samples of 19 sampling stations collected in the period from March to November in 1997. Water temperature was in the range of $8.3{\sim}35.3{\circ}^C$, with thermocline appearing in summer. Dissolved oxygen also showed similar verticle variation to temperature. Secchi depth was very shallow with a range of 0.1~1m. Suspended solids ranged from 11.3 mg/1 to 2143.3 mg/1, and seemed to be affected by the amount of rainfall and the standing stocks of phytoplankton. Nutrient concentrations were higher in tributaries, and decreased with downflow. Nutrients were low in the summer and early autumn when algal blooms occur, and high in the early spring and winter. The Trophic State Index showed that the Asan Reservoir is in a hypertrophic condition．

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.2
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• pp.259-264
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• 2003

One Clausius inequality based on an apparatus with a single thermal reservoir is reviewed. Some intricate issues regarding the apparatus are brought up and therefore a preferred way to interpret the Kelvin-Planck statement is suggested. Then it is shown that another Clausius inequality can be established from a direct application of the proposition regarding the efficiency of a Carnot cycle. The establishment is based on an apparatus with two reservoirs, and the resultant inequality involves the temperature of external reservoir. Finally, a different apparatus which also has two thermal reservoirs is utilized to compare the cyclic integral of the former inequality with the one of the latter resulting in the proof of the former inequality which involves the temperature at the system boundary. The applications and limitations of these two Clausius inequalities are discussed.

• Korean Journal of Ecology and Environment
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• v.40 no.4
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• pp.581-585
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• 2007

Swarm formation of Scapholeberis kingi Sars 1903 was observed in a shallow reservoir on 27 May 2007 (Dongpan Reservoir) for the first time. Dense swarms composed of asexual females, only occurred during daytime (13:00-17:00, local time) at the littoral zone. Correlation between density of S. kingi and environmental factors such as water temperature and density of juvenile fish were positively significant. Therefore, it is suggested that the swarming of S. kingi seems to be induced for predator avoidance than increase of mating chance, and water temperature may affect their swarming behavior.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.13 no.1
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• pp.38-47
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• 2001

The operation characteristics of variable conductance heat pipe(VCHP) were numerically investigated by using 1-dimensional diffuse-front model. For different boundary conditions, the amount of non-condensible gas charge and dimension of gas reservoir were obtained by iterative calculation. It is found that the amount of non-condensible gas charge and dimensions of gas reservoir have an effect on the temperature control of condenser for the given operating condition of VCHP. The numerical results show that VCHP has an excellent capability of temperature control when subjected to a change in the heat input.

• Korean Journal of Ecology and Environment
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• v.41 no.4
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• pp.472-484
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• 2008

The calibrated Andong Reservoir hydro-dynamic module (PART I) of the 2-dimensional hydrodynamic and water quality model, CE-QUAL-W2 [v3.2], was applied to examine the dynamics of total phosphorus, and chlorophyll $\alpha$ concentration within Andong Reservoir. The modeling effort was supported with the data collected in the field for a five year period. In general, the model achieved a good accuracy throughout the calibration period for both chlorophyll ${\alpha}$ and total phosphorus concentration. The greatest deviation in algal concentration occurred on $10^{th}$ October, starting at the layer just beneath the surface layer and extending up to the depth of 35 m. This deviation is principally attributed to the effect of temperature on the algal growth rate. Also, on the same date, the model over-predicts hypolimnion and epilimnion total phosphorus concentration but under-predicts the high concentrated plume in the metalimnion. The large amount of upwelling of finer suspended solid particles, and re-suspension of the sediments laden with phosphorus, are thought to have caused high concentration in the epilimnion and hypolimnion, respectively. Nevertheless, the model well reproduced the seasonal dynamics of both chlorophyll a and total phosphorus concentration. Also, the model tracked the interflow of high phosphorus concentration plume brought by the turbid discharge during the Asian summer monsoon season. Two different hypothetical discharge scenarios (discharge from epilimnetic, and hypolimnetic layers) were analyzed to understand the response of total phosphorus interflow plume on the basis of differential discharge gate location. The simulated results showed that the hypolimnetic discharge gate operation ($103{\sim}113\;m$) was the most effective reservoir structural control method in quickly discharging the total phosphorus plume (decrease of in-reservoir concentration by 219% than present level).

• Journal of Korean Society on Water Environment
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• v.26 no.2
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• pp.231-242
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• 2010

The objective of study was to determine an optimal location of a float-type curtain weir in Daecheong Reservoir and to assess its effectiveness for the control of algal blooms in the reservoir. CE-QUAL-W2, a laterally averaged two-dimensional hydrodynamic and eutrophication model, was modified to accommodate vertical displacement of the weir according to water surface fluctuation and applied to simulate the reservoir hydrodynamics and water quality changes for the reservoir. The model calibrated in a previous study was updated and validated for different hydrological conditions representing drought year (2008) and normal year (2006) for the study, and adequately simulated the temporal and spatial variations of water temperature, nutrients and algal (Chl-a) concentrations. The effectiveness of curtain weir on the control of algal bloom was evaluated by applying the validated model to 2001 and 2006 assuming 9 scenarios for different installation locations. The reduction rates of algal concentration were placed in the range of 11.2~40.3% and 20.3~56.7% for 2001 and 2006, respectively. Although, the performance of curtain weir was slightly varied for different locations and different hydrological years, overall, the performance was improved as the weir was installed further downstream.

• ALGAE
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• v.20 no.4
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• pp.333-343
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• 2005

Spatial and temporal variations of environmental factors and phytoplankton community were investigated in the three stations of Andong Reservoir in 1997 and 2003. The changes of physico-chemical water quality and phytoplanktonic biomass were higher in 2003 than that of 1997, due to rainfall difference. The concentration of total nitrogen (TN) and total phosphorus (TP) in the reservoir decreased, but total nitrogen fell relatively more between them. TN/TP ratio decreased from 109 to 90 showing no change at the downstream but a big decrease at the midand upstream. Predominant phylum of phytoplankton in Andong Reservoir were six genus that composed to Anabaena, Aphanizomenon and Microcystis of Cyanophyceae, Cosmarium and Scenedesmus of Chlorophyceae and Synedra of Bacillariophyceae, respectively. Among the observed phytoplankton, diatom Synedra occured as the maximum amount of 3,400 cells mL$^{-1}$ even at the above 30°C. Green algae Scenedesmus observed along with Microcystis. It seemed to be compete with Microcystis during the high water temperature period. Although trophic state of Andong Reservoir was decreased, the standing crops of phytoplankton were increased. Moreover bluegreen algae, Aphanizomenon and Microcystis in the region of upstream to midstream and diatom, Synedra in the region of midstream to downstream were increased until to reach the algal bloom, respectively. It seemed necessary to attention the changes of blue-green algae Aphanizomenon, that has an ability of nitrogen fixation.

• Journal of Environmental Science International
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• v.9 no.2
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• pp.115-123
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• 2000

The dynamics of water quality and phytoplankton population had examined by monthly sampling from the upper to the lower part of watergate in an artificial Shihwa Reservoir in which situated near newly cities and incustrial complex on the west coast of Korea from January 1997 to December 1998. Among environmental factors, yearly average concentration of chl-a, TN and TP seemed to eutrophic or hypertrophic conditions that ranged 146.4~245.8 $\mu\textrm{g}$/$\ell$, 1.6~2.7 mg N/$\ell$, 258~448 $\mu\textrm{g}$ P/$\ell$, 26.9~80.7 $\mu\textrm{g}$/$\ell$, 1.0~2.4 mgN/$\ell$ and 74~239 $\mu\textrm{g}$P/$\ell$ respectively. Water quality was extremely deteriorated to consistently accumulation into inner reservoir by load of pollutants from autochthonous and allochthonous until early July 1997 after embankment. Water pollution of Shihwa Reservoir was remarkble on the biological condition with largely persistent bloom of phytoplankton and increase rate of standing crops was 2.4/yr. The development trend of phytoplankton in water ecosystem were closely related to increse and decrease of physico-chemical factors and those scale seemed to control by nutrient contents. Inflow of seawater into reservoir to object of repair of water quality. As to see dominant species, composition of those composed to mostly freshwater algae before inflow of seawater such as Selenastrum capricornutum of green algae, cyclotella atomus, C. meneghiniana of diatom and Microcystis spp. of blue-green algae and the other hand brackish algae were dominated after inflow of seawater such as Chaetoceros dicipiens, Skeletonema costatum of diatom, Dinophysis acuminata, Gymnodinium mikimotoi, G. sanguineum, Gyrodinium spirale, Prorocentrum minmum of dinoflagellate and Eutreptiella gymnastica of euglenoid. Moreover, small flagellates including Chroomonas spp. of cryptomonad were abundant throughout the year. The cause of water deterioration during fill of the freshwater were complexly supported with extra and intra parameters. The variation pattern of phytoplankton were related to water temperature and salinity by inflow of seawater based to plentiful nutrients. The dynamics of phytoplankton were assessed to ecosystem that clearly condition of dominant by unique or a few angel species seasonally.