• Korean Journal of Ecology and Environment
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• v.36 no.3 s.104
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• pp.336-343
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• 2003

Two types of statistical models, simple and multivariate log linear models, were studied for continuity simulation and trend analysis of water qualities in incoming flows to Lake Paldang. Water quality is a function of one independent variable (flow) in the simple log linear model, and of three different variables (flow, time, and seasonal cycle) in multivariate model. The independent variables act as surrogate variables of water quality in both models. The model coefficients were determined by the monthly data. The water qualities included 5-day Biochemical Oxygen Demand ($BOD_5$), Total Nitrogen (TN), and Total Phosphorus (TP) measured from 1995 to 2000 in the South and the North branches of Han River and the Kyoungan Stream. The results indicated that the multivariate model provided better agreements with field measurements than the simple one in a31 attempted cases. Flow dependency, seasonality, and temporal trends of water quality were tested on the determined coefficients of the multivariate model. The test of flow dependency indicated that BOD concentrations decreased as the water flow increased. In TN and TP concentrations, however, there were no discernible flow effects. From the temporal trend analyses, the following results were obtained: 1) no trends on BOD at all three upstreams, 2) increase on TN at the South Branch and the Kyoungan Stream, 3)decrease on TN at the North Branch,4) no trends on TP at the North and the South Branches and 5) increase on TP at the Kyoungan Stream by 3 to 8% per years. The seasonality test showed that there were significant seasonal variations in all three water qualities at three incoming flows.

• Journal of Korean Society on Water Environment
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• v.29 no.5
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• pp.641-647
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• 2013

We installed mesocosms including zooplankton, fishs, artificial marshy land and aquatic macrophytes in Kyoungan stream to study the reduction effects of algae from Sep. 16 to Oct. 28, 2011. The control tendency of phytoplankton taxa was compared by analyzing community structure and dominant species in each mesocosm. Under the condition where Bluegill was absent, Daphnia similoides showed good effect of algal control since it has large food area and has high grazing pressure. Bluegill selectively preys upon large zooplankton, Daphnia similoides, as it also preys on small zooplanktons that flow in. In condition that Bluegill was absent, Daphnia similoides preyed selectively large phytoplankton (Cryptomonas ovata). Due to the shading of light, removal of nutrients and providing refuge for small zooplanktons, aquatic macrophytes and artificial marshy land showed high level of algal control. In corrals with aquatic macrophytes and artificial marshy land, the dominancy of genus Coelastrum and Pediastrum, which are difficult for small zooplanktons to feed on, relatively increased. In conclusion, under conditions of small number of predators such as Bluegill, Daphnia similoides is thought to be useful in algal bloom; however, when lots of predators are present, using small sized zooplanktons along with artificial marshy land and aquatic macrophytes is thought to be more useful than using large zooplanktons.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.9
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• pp.978-988
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• 2005

A three-dimensional dynamic model was applied to Lake Paldang, Han River in this study. The model was calibrated and verified using the data measured under different ambient conditions. The model results were in reasonable agreements with the field measurements in both calibration and verification. Utilizing the validated model, we analyzed the spatial and temporal distributions of temperature, current, residence time, and spreading pattern of incoming flows within the lake. Relatively low velocity and high temperature were computed at the surface layer in the southern region of the Sonae island. The longest residence time within the lake was predicted in the southern region of the Sonae island and the downstream region of the South Branch. This can be attributed to the fact that the back currents caused by the dam blocking occur mainly in these regions. Vertical thermal profiles indicated that the thermal stratifications would be occurred feebly in early summer and winter. During early spring and fall, it appeared that there would be no discernible differences at the vertical temperature profiles in the entire lake. The vertical overturns, however, do not occur during these periods due to an influence of high discharge flows from the dam. During midsummer monsoon season with high precipitation, the thermal stratification was disrupted by high incoming flow rates and discharges from the dam and very short residence time was resulted in the entire lake. In this circulation patterns, the plume of the Kyoungan stream with smallest flow rate and higher water temperature tends to travel downstream horizontally along the eastern shore of the south island and vertically at the top surface layer. The model results suggest that the Paldang lake should be a highly hydrodynamic water body with large spatial and temporal variations.