• Korean Journal of Ecology and Environment
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• v.51 no.4
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• pp.287-298
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• 2018

The zooplankton community and environmental factor were investigated on a weekly basis from March to November 2015 in Lake Paldang, Korea. The seasonal succession of zooplankton community structure was influenced by hydraulic and hydrological factors such as inflow, outflow and rainfall. However, the hydraulic retention time in 2015 (16.3 day) was affected by the periods of water shortage that had continued since 2014 and increased substantially compared to 2013 (7.3 day). Therefore, the inflow and outflow discharge were decreased, and the water quality (COD, BOD, TOC, TP, Chl-a) of Lake Paldang (St.1) was the same characteristics as the river type Bukhan river (St.3), compared with the lake type Namhan river (St.2) and Gyeongan stream (St.4). Zooplankton community dominated by rotifers (Keratella cochlearis, Synchaeta oblonga) in spring (March to May). However, Copepod (Nauplius) and Cladoceran (Bosmina longirostris) dominated in St.4. In summer (June to August), there was a few strong rainfall event and the highest number of individuals dominated by Keratella cochlearis (Rotifera) and Difflugia corona (Protozoa) were shown during the study period. In autumn (October to November), the water temperature was decreased with decrease in the total number of individuals showing Nauplius (Copepoda) as the dominant species. As a result of the statistical analysis about zooplankton variation in environmental factors, the continuous periods of water shortage increased the hydraulic retention time and showed different characteristic for each site. St.1, St.3 and St.2, St.4 are shown in the same group (p<0.05), showing the each characteristics of river type and lake type. Therefore, the water quality of catchment area and distribution of zooplankton community would be attributed to hydraulic and hydrological factors.

• Journal of Korea Water Resources Association
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• v.43 no.2
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• pp.167-185
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• 2010

One of the most difficult problems in estimating design floods is how to determine design storms. More specifically, the design storm problems turn into how to determine temporal and spatial distribution of the storm. In this study, Thiessen-Weighted BlocKing-type(TWBK) moving storms are suggested to resolve the design storm problems and their applicability is investigated. These moving storms are applied for 100-year 48-hour design flood estimation in Han river basin using a physics-based distributed rainfall-runoff model. Simulated floods from moving storms are compared with frequency-based ones estimated from observed floods.

• 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 Agricultural and Forest Meteorology
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• v.18 no.2
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• pp.88-98
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• 2016

The storage variation in the vadose zone at a hillslope is important to understand the hydrological process. This study explores seasonal changes of soil water storage at a hillslope scale. The study was conducted on a hillslope of Beomrunsa, located in the Seolma-cheon river basin in Paju-si, Gyeonggi-do. Using soil moisture measurements through Time Domain Reflectometry (TDR), storage, discharge, and response constant were calculated for all monitoring points on a hillslope between March and November, 2010. This study found that temporal changes in storage are resulted from the rainfall distribution patterns. Analysis of the spatial changes in storage indicated that the soil water storage tends to increase towards the downslope direction. The discharges calculated based on the soil water measurements exhibited a high correlation with observation discharge. The storage response constant was high during the autumn which demonstrates the increased contribution from upslope is responsible for the occurrence of soil water recharge during autumn.

• Journal of Korea Water Resources Association
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• v.56 no.2
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• pp.75-89
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• 2023

As the Mekong River basin is a nationally shared river, it is difficult to collect precipitation data, and the quantitative and qualitative quality of the data sets differs from country to country, which may increase the uncertainty of hydrological analysis results. Recently, with the development of remote sensing technology, it has become easier to obtain grid-based precipitation products(GPPs), and various hydrological analysis studies have been conducted in unmeasured or large watersheds using GPPs. In this study, rainfall-runoff simulation in the Mekong River basin was conducted using the SWAT model, which is a quasi-distribution model with three satellite GPPs (TRMM, GSMaP, PERSIANN-CDR) and two GPPs (APHRODITE, GPCC). Four water level stations, Luang Prabang, Pakse, Stung Treng, and Kratie, which are major outlets of the main Mekong River, were selected, and the parameters of the SWAT model were calibrated using APHRODITE as an observation value for the period from 2001 to 2011 and runoff simulations were verified for the period form 2012 to 2013. In addition, using the ConvAE, a convolutional neural network model, spatio-temporal correction of original satellite precipitation products was performed, and rainfall-runoff performances were compared before and after correction of satellite precipitation products. The original satellite precipitation products and GPCC showed a quantitatively under- or over-estimated or spatially very different pattern compared to APHPRODITE, whereas, in the case of satellite precipitation prodcuts corrected using ConvAE, spatial correlation was dramatically improved. In the case of runoff simulation, the runoff simulation results using the satellite precipitation products corrected by ConvAE for all the outlets have significantly improved accuracy than the runoff results using original satellite precipitation products. Therefore, the bias correction technique using the ConvAE technique presented in this study can be applied in various hydrological analysis for large watersheds where rain guage network is not dense.

• Journal of the Korean Society for Marine Environment & Energy
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• v.6 no.4
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• pp.24-36
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• 2003

In this study, we estimated the seasonal fluctuations of water quality and effect of small tide embankment in coastal water around the Muan Peninsula, which is located in the northern part of Mokpo city, and layer farming ground is spread around there. Some physical and chemical factors were analyzed to characterize water quality from Jan. to Oct. in 1994. The results were as follows: Dissolved oxygen was slightly under saturation in the almost areas of July, and in some bottom layer at ebb tide of October. Distribution of COD showed high values that over 2㎎/L in October and flood tide of April by the discharge of freshwater and resuspension of benthic sediment, which exceeded water quality criteria II. Maximum values of dissolved inorganic nitrogen ware appeared in surface layer during the flood tide of October, while minimum of that showed in surface layer in April. Concentration of dissolved inorganic phosphorus was higher at July than the others, which ranged from 0.24 to 2.08㎍-at/L. Mostly mean values of N/P ratio were lower than 16, it mean that nitrogen is more limiting nutrient than phosphorus for the growth of phytoplankton. The values of eutrophication index were in the range of 0.07~0.81. However, very high values due to increase of COD were estimated near the tide embankment and southern part in relation to tidal current in October. Water quality around tide embankment was suddenly changed worse within a short period after opening the water gate during the rainfall.

• 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.

• 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.