• Korean Journal of Soil Science and Fertilizer
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• v.16 no.2
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• pp.112-118
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• 1983

Rainfall factor (R-factor), which is an index for the prediction of soil erosion in the Universal Soil Loss Equation (USLE), was computed from 21 years rainfall data at 51 locations in Korea. The values of R-factor are from 200 to 300 in the eastern part, and 300 to 700 in the western and southern part of the peninsula. Curvilinear regressions exist between annual rainfall and annual R-factor or between monthly rainfall and monthly R-factor. The R-factor can be estimated from the regression equation as a function of the amount of rainfall. According to the comparison between the actual soil loss measured by lysimeter and the soil loss predicted by the USLE, EI 30 for R-factor was recognized as a suitable factor for the USLE in korea.

• Journal of Korea Water Resources Association
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• v.42 no.9
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• pp.747-758
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• 2009

In this study, long-term variabilities of rainfall-occurrence characteristics are analyzed using rainfall data at Seoul, which is the longest data record existing in world. first, the accuracy of Chukwooki data set (CWK) are evaluated in view of rainfall-occurrence probability by analyzing the transition probabilities and occurrence characteristics based on Markov chain. And long-term inter-monthly variabilities of transition probabilities are analyzed using two dimensional LOWESS regression. From the results of analyzed transition probabilities and occurrence characteristics, it is different that rainfall-occurrence characteristics between CWK and modern rain gage data set (MRG) for original rainfall data sets (M00). For characteristics of rainfall series, occurrences probabilities of rainfall are increased and durations of each rainfall are shorter than past. And from the results of analyzing the long-term inter-monthly variabilities of transition probabilities, in case of M20, lengths of dry spells between CWK and MRG are not different significantly and lengths of wet spells are decreased persistently after A.D. 1830. Especially, decreasing trend for lengths of wet spells at recent september are appeared significantly. These results are considered with increasing trend of recent rainfall, it is concluded that recent frequencies and intensities of rainfall are increasing.

• Proceedings of the KSRS Conference
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• v.1
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• pp.122-125
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• 2006

The distribution of phytoplankton pigments were studied bimonthly at four stations from the mouth of Mahanadi River at Paradip to the 36.7km off coast in Bay of Bengal during April 2001 to December 2002. Bottom depth was shallower than 40m in all stations. The pigment concentration of Chl-a was measured. It increased from surface to bottom in the water column. The water column integrated chlorophyll-a concentration (Chl-a) varied between 6.1 and $48.5mg{\cdot}m-^2$ with peaks during monsoon period (Aug & Oct). Spatial distribution of salinity depended strongly on freshwater runoff. The salinity was 5psu at river mouth and 25.15psu at offshore in monsoon period; however it was 30psu at the river mouth in summer. We found a linear relationship between the amount of river discharge and integrated Chl-a in coastal region from 2 years observations. Extending this result, we analyzed rainfall and coastal Chl-a using satellite data. The relationship between the river discharge and monthly accumulated rainfall estimated from TRMM and others data sources was analyzed in 2001 and 2002 using Giovanni infrastructure provided by NASA. The result depended on the specified area on TRMM images; the river delta area had sharper relationship than wider rain catchments area. Moreover, the relationship between monthly averaged Chl-a derived from SeaWiFS and monthly accumulated rainfall estimated from TRMM was analyzed from 1998 to 2005. It was clear that the broom in monsoon period was strongly controlled by rainfall on river delta.

• Journal of The Korean Society of Agricultural Engineers
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• v.47 no.6
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• pp.83-92
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• 2005

Natural environment of the Wolgokri stream watershed, located in Chuncheon, Gangwon province, Korea, has been well preserved as a traditional agricultural watershed. To analyze characteristics of NPS pollution generated from an mountainous agricultural watershed, the flow and water qualities of the study watershed were monitored and were analyzed to estimate pollution loads. Annual runoff volume ratio was $70.4\%$. Concentrations of T-N, T-p, COD, and TOC were higher when monthly rainfall was between $0\~30mm$ than those when monthly rainfall was between $30\~70mm$. However, the concentrations varied considerably when monthly rainfall was higher than 100mm. The flow weighted mean concentrations(mg/L) of BOD, COD, TOC, $NO_3-N$, T-N, T-P and SS were 1.96, 2.72, 3.32, 1.41, 4.70, 0.187 and 13.36, respectively. The BOD, SS, T-N and T-P loads of July, 2004 were $48\%,\;17\%,\;51\%\;and\;32\%$ of annual load, respectively. The BOD, COD, TOC, $NO_3-N$, T-N, T-p, and SS loads (kg/ha) from Mar. 2004 to Apr. 2005 were 19.09, 26.55, 32.39, 13.85, 45.92, 1.887 and 130.18, respectively. The highest concentrations of BOD, NO3-N, T-N, T-p, SS, COD and TOC were found before the flow reached the peak runoff, possibly due to the first flushing effect. Generally, pollution loads of the Wolgokri watershed were not that significant. Phosphorus load, however, was higher enough to cause eutrophication in the receiving water body It was recommended that best management practices need to be implemented to reduce phosphorus sources.

• Proceedings of the Korea Water Resources Association Conference
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• 2001.05a
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• pp.7-14
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• 2001

In this study, we characterized the variation of sampling errors using the Waymire-Gupta-rodriguez-Iturbe multi-dimensional rainfall model (WGR model). The parameters used for this study are those derived by Jung et al. (2000) for the Han River Basin using a genetic algorithm technique. The sampling error problems considering in this study are those far using raingauge network, satellite observation and also for both combined. The characterization of sampling errors was done for each month and also for the downstream plain area and the upstream mountain area, separately. As results of the study we conclude: (1) The pattern of sampling errors estimated are obviously different from the seasonal pattern of mentally rainfall amounts. This result may be understood from the fact that the sampling error is estimated not simply by considering the rainfall amounts, but by considering all the mechanisms controlling the rainfall propagation along with its generation and decay. As the major mechanism of moisture source to the Korean Peninsula is obviously different each month, it seems rather norma1 to provide different pattern of sampling errors from that of monthly rainfall amounts. (2) The sampling errors estimated for the upstream mountain area is about twice higher than those for the down stream plain area. It is believed to be because of the higher variability of rainfall in the upstream mountain area than in the down stream plain area.

• Journal of Environmental Science International
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• v.28 no.6
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• pp.571-579
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• 2019

In this study, monthly average values of BOD, COD, and TOC observed for 10 years (2008-2017) in the Nam River were estimated, and monthly variations of BOD, COD, and TOC were analyzed. Monthly average COD was always higher than monthly average BOD; monthly average TOC was high from June to September when rainfall was high. Monthly correlation coefficients between BOD and COD ranged from 0.57 to 0.94, those between BOD and TOC from 0.45 to 0.93, and those between COD and TOC from 0.75 to 0.93. The correlation coefficients were high from November to February when rainfall was low. Regression analyses for monthly average water quality data of the Nam River classified into dry season (October to April) and wet season (May to September) were conducted. Correlation coefficients were higher in the dry season than those in the wet season, and the determination coefficients of linear regression functions for BOD and COD with TOC were also higher in the dry season than those in the wet season. From this study, it can be concluded that it is appropriate to use monthly data to analyze the correlations among BOD, COD, and TOC in the stream. To analyze the relationship between TOC flowing into the stream and BOD/COD, it was found that seasonal characteristics should be considered.

• Proceedings of the Korea Water Resources Association Conference
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• 1996.05a
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• pp.259-267
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• 1996

• Journal of Korea Water Resources Association
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• v.41 no.2
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• pp.173-184
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• 2008

Climatic water balance has been applied to obtain quantity of various hydrologic components. Hydrologic information is estimated by comparison between rainfall and evapotranspiration under complex terrain condition. Water deficit is defined as that subtraction of actual supply from climatic demand. The water deficit will occur, when monthly evapotranspiration exceed monthly rainfall. Contrary water surplus is defined as that surplus water after meeting the demand by plants. The water surplus will be occurred when monthly rainfall exceeds monthly evapotranspiration. Finally, the discrete moisture indices were calculated and mapped for the whole watershed to estimate dryness and wetness status using the climatic water balance approach. The result of this study can properly interpret the real drought and non drought. Based upon the results, it can be concluded that the climatic water balance model is useful to monitor water conditions for the watershed.

• Journal of Korean Society on Water Environment
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• v.21 no.3
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• pp.277-283
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• 2005

This paper aimed to compare the daily water quality as well as the hydrological data gathered for the past two years (2000 to 2001) between the two influent rivers of Paldang reservoir. The analysis also has been carried out to draw out the factors that affect the water quality at the dam site, where the main drinking water drawing point is located. The relationship between total amount of monthly rainfall and monthly inflow showed $r^2=0.74$ (p<0.05). The highest peak of inflow of influent rivers recorded in August and September (in the year of 2000) and July and August (2001). Average inflows of influent rivers in 2000 and 2001 are calculated at 209.0, 161.5 CMS (Bughangang), 268.6, 148.2 CMS(Namhangang), and 7.8, 5.0 CMS (Gyeongancheon). The formula which was driven from the relationship between inflow and COD load of influent rivers, explained that COD concentration in general increased with the inflow. But during the rainy seasons (July, August, and September), COD concentration decreased according to the increase of inflow. The daily rainfall and COD concentration(or load) during the rainy season (August and September in the year of 2000, July and August in 2001) indicated that the peak of COD load correspond with the rainfall, which decreased sharply after 3 or 4 days. The reason was thought that the high COD load was diluted rapidly by the rain flow. Water temperature, pH and conductivity measured at dam site decreased obviously when the inflow sharply increased. Peak period of total phosphorus concentration coincided with that of inflow. In rainy season, chlorophyll-a concentration decreased obviously as the inflow increased. The reason can be ascribed to the flushing effect caused by the operation of floodgate.

• Journal of Wetlands Research
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• v.20 no.4
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• pp.338-344
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• 2018

In this study, the surface air temperature (SAT) and the dew-point temperature (DPT) are applied as the covariance of the location parameter among three parameters of GEV distribution to reflect the non-stationarity of extreme rainfall due to climate change. Busan station is selected as the study site and the monthly maximum daily rainfall depth from May to October is used for analysis. Various models are constructed to select the most appropriate co-variate(SAT and DPT) function for location parameter of GEV distribution, and the model with the smallest AIC(Akaike Information Criterion) is selected as the optimal model. As a result, it is found that the non-stationary GEV distribution with co-variate of exp(DPT) is the best. The selected model is used to analyze the effect of climate change scenarios on extreme rainfall quantile. It is confirmed that the design rainfall depth is highly likely to increase as the future DPT increases.