• Journal of the Korean Society of Marine Environment & Safety
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• v.19 no.4
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• pp.315-326
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• 2013

This study investigated the temporal-spatial distribution and variations in water quality parameters (temperature, salinity, pH, DO, COD, SPM, DIN, DIP, silicate, TN, TP, and chlorophyll-a) in the coastal area of Jeju, Korea, adjacent to aquaculture ponds (Aewol-ri, Haengwon-ri, Pyosun-ri, and Ilkwa-ri). Data were collected bimonthly from February 2010 to December 2011. A principal component analysis (PCA) identified three major factors controlling variations in water quality during the sampling period. Aquaculture effluent water led to large changes in nutrient levels. The highest nutrient values were observed during the investigation period. The relatively large increase in organic matter at the sampling stations coupled with sea area runoff events during the summer rainy period. Variation in chlorophyll-a concentration was mainly driven by meteorological factors such as air temperature and rainfall in the coastal areas of Aewol and Haengwon. In the coastal areas of Pyosun and Ilkwa, pollution was caused by anthropogenic factors such as discharge of aquaculture effluent water. High nutrient concentrations at the majority of the coastal stations indicate eutrophication of coastal waters, especially within a distance of 300 m and depth of 10m from drainage channels. Coastal eutrophication driven by aquaculture effluent may be harmful inshore. Events such as eutrophication may potentially influence water pollution in aquaculture ponds when seawater intake is detected because of aquaculture effluent water.

• Journal of Korean Society for Geospatial Information Science
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• v.18 no.4
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• pp.21-30
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• 2010

In this paper, the parallel distributed rainfall runoff model(K-DRUM) using MPI(Message Passing Interface) technique was developed to solve the problem of calculation time as it is one of the demerits of the distributed model for performing physical and complicated numerical calculations for large scale watersheds. The K-DRUM model which is based on GIS can simulate temporal and spatial distribution of surface flow and sub-surface flow during flood period, and input parameters of ASCII format as pre-process can be extracted using ArcView. The comparison studies were performed with various domain divisions in Namgang Dam watershed in case of typoon 'Ewiniar' at 2006. The numerical simulation using the cluster system was performed to check a parallelization effectiveness increasing the domain divisions from 1 to 25. As a result, the computer memory size reduced and the calculation time was decreased with increase of divided domains. And also, the tool was suggested in order to decreasing the discharge error on each domain connections. The result shows that the calculation and communication times in each domain have to repeats three times at each time steps in order to minimization of discharge error.

• Korean Journal of Ecology and Environment
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• v.41 no.2
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• pp.206-215
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• 2008

Temporal and spatial distributions of salinity, temperature, dissolved oxygen (DO), and turbidity were investigated at seven sites in the upper regions of brackish Lake Sihwa with a limited water exchange, from March to October 2005. During the study period, salinity and temperature varied $0.1{\sim}29.9\;psu$ and $4.7{\sim}28.1^{\circ}C$, respectively, depending on seasons and sites sampled. A distinct halocline profile showing the maximum density gradient (difference over $20\;psu\;m^{-1}$ between surface and bottom layers) was observed during the rainy season, due to the decrease of salinity in surface layers by freshwater inflow. This result implies that rainfall event is the important factor forming the halocline. On the other hand, the depth and location of haloeline varied with the amount of seawater through the sluice gates and the operation systems (inflow or outflow). High DO (over 300% saturation) was observed at surface layer above the halocline in April when red tide occurred, whereas low DO (below 20% saturation) was at the bottom layer below the halocline in the rainy season. Turbidity ranged $1.5{\sim}80.3\;NTU$ showing the maximum turbidity at the layers above or upper the halocline. As a result, the distributions of DO and turbidity in the upper regions of brackish Lake Sihwa were largely affected by the variation of salinity. Also, when the halocline was formed, the water quality between upper and lower water layers may be expected completely different. This study suggests that the physicochemical characteristics of water in the brackish regions are closely associated with the causes of eutrophication such as red tide and DO deficit.

• Korean Journal of Ecology and Environment
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• v.51 no.4
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• pp.331-344
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• 2018

Lotic organisms in streams are affected by natural and anthropogenic disturbances such as increase of heavy rainfall event caused by climate change and flow regime change caused by weir constructions. Based on domestic and foreign literature, 157 Korean benthic macroinvertebrate taxa were selected species as potential lotic candidates. Three shoreline sites (total 54 samples) were surveyed consecutively before ('08~'09), during ('10~'12) and after ('13~'16) the construction of the weirs (Gangcheon, Yeoju and Ipo weir) in the Namhan-River for tracing changes of lotic communities. As a result, water flow of the Ipo-wier and water quality variables such as T-N, T-P, BOD5, etc. of the weir section revealed no significant changes. Physical habitat conditions such as the flow velocity and streambed substrate evidently changed. Particulary, flow velocity measured at sampling points along with each microhabitat drastically decreased and particle size of streambed substrate steadily decreased after weir constructions. Lotic organisms also decreased after construction, especially Hydropsychidae (insecta: Trichoptera) acutely decreased from $3,526ind.\;m^{-2}$ to $2ind.\;m^{-2}$ As a result of CCA, lotic species such as Hydropsyche valvata, Hydropsyche kozhantschikovi, Cheumatopsyche brevilineata, Cheumatopsyche KUa, Macrostemum radiatum, etc. correlated with the flow velocity, streambed substrate. Therefore, the decrease of the flow velocity and substrate size after weir construction seemed to be closely related to the decrease of the individual abundances of the lotic organisms independently of water quality. In order to evaluate the influence of the ecosystem on the flow regime change more accurately, it is necessary to study the indicator species based on the resistance or preference of the flow.