• Journal of Korean Society on Water Environment
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• v.30 no.6
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• pp.622-631
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• 2014

The purpose of this research was to find a proper disposal rainfall extent to improve water quality. SWMM was applied to select catchment area and tested first flush load and rainfall extent. BOD 40mg/L was selected to dispose the first flush and sewer overflow with the same as the criteria of Sewerage Act. Design rainfall, BOD load ratio of first flush sewer overflow, and the ratio of disposal flow were analyzed under various rainfall distribution. BOD load and design rainfall to treat overflow in situation of first flush extent with 4.3~17.4% were 56~87% and 3.8~6.8 mm/day, respectively. In urban area, first flush loads were not correspond to land activities, but tend to increase with increasing rainfall amount and drainage area. The more the distribution of rainfall is similar to Huff-frontal or central distribution of rainfall, the more increase the first flush loads.

• Atmosphere
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• v.23 no.1
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• pp.23-32
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• 2013

Ensemble sensitivity has been recently proposed as a method to analyze the dynamics of severe weather events. We adopt it to investigate the physical mechanism which caused the heavy rainfall over the Korean Peninsula on 6th August 2003. Two rainfall peaks existed in this severe weather event. The selected response functions are 1 hour accumulated rainfall amount of each rainfall peak. Sensitivity fields were calculated using 36 ensemble members which were generated by WRFDA. The sensitive regions for the first rainfall peak are located over the Shandong Peninsula and the Yellow Sea at 12 hours before the first rainfall peak. However, the 12-h forecast sensitivity for the second rainfall peak is revealed near Typhoon ETAU (0310) and midlatitude trough. These results show that the first rainfall peak was induced by low pressure which located over the northern part of the Korean Peninsula while the second rainfall peak was caused by the interaction between typhoon ETAU and midlatitude trough.

• Journal of Korean Society of Water and Wastewater
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• v.18 no.3
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• pp.320-330
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• 2004

Most of domestic city is served combined sewer system among various sewer system like as separate sanitary, combined sewer system and storm sewers. During the wet weather, sewer and rainfall have been overflowed because it is over capacity of the combined sewer system; that is called combined sewer overflows(CSOs) This research was carried out to investigate runoff characteristics of combined sewer and to evaluate the effective CSOs volume in Hong-Chun gun. During wet weather, SS load of first rainfall at H-1, H-2, and H-3 were 600kg/event, 370kg/event, and 289kg/event, respectively. 55 load of second rainfall were 216kg/event, 113kg/event, and 37.2kg/event. When the first rainfall, event mean concentrations(EMCs) at each site were 702mg/L, 816mgjL and 861.5mg/L. The second rainfall's event mean concentrations(EMCs) were 99.9gm/L, 161.9mg/L, 103.6mg/L. Rrst flush coefficient b at each site were 0.237,0.166, and 0.151. When the first rainfall, the flow containing 80% of pollutant mass of CSOs at each site were 0.55, 0.23, 0.48 in first rainfall, respectively. The case of second rainfall were 0.79, 0.83, 0.81. Most of all, characteristics of rainfall like as analysis of first-flush, CSOs volume, pollutant loadings is investigated to decide intercepted volume for control of CSOs.

• Korean Journal of Plant Resources
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• v.19 no.2
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• pp.340-343
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• 2006

This study was conducted to find out the effect of rainfall time on growth and seed quality in safflower. Rainfall was done artificially and the treatment of rainfall time was divided into 6 parts. Each rainfall treatment was done from the first day of flowering up to the fifth day after flowering, from sixth day after flowering to the tenth day after flowering, from the eleventh day after flowering to the fifteenth day after flowering, from sixteenth day after flowering to twentith day after flowering, from the twenty first day after flowering to the twenty fifth day after flowering and from twenty sixth day after flowering to thirtith day after flowering. Rainfall time after flowering did not affect disease occurrence on the upper part and flower bud of safflower, which were infected at were 3.3 and 1, respectively. Ripened grain found on the main stem and primary branch was 37.4% and 65.0% at first day to the fifth day and sixth day to the tenth day rainfall periods after flowering, respectively. Yield was decreased by 14% in the sixth day up to the tenth day and eleventh day up to the fifteenth day rainfall periods (282-281kg/10a) compared to the one under control (327kg/10a). Hunter's L value was 73.5 and 69.9 in twenty first up to the twenty fifth day and twenty sixth up to the thirtith day rainfall periods after flowering, which decreased significantly to 79.3 under non-rainfall period. Therefore, it can be concluded that the optimum harvest time is twenty fifth day after flowering to maintain seed quality at rainfall time and before harvesting period.

• Journal of Korean Society of Water and Wastewater
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• v.25 no.3
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• pp.407-417
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• 2011

Nowadays, the high land use, mainly used for urbanization, is affecting runoff loads of non-point pollutants to increase. According to this fact, increasing runoff loads seems like to appear that it contributes to high ratio of pollution loads in the whole the pollution loads and that this non-point source is the main cause of water becoming worse quality. Especially, concentrated pollutants on the impermeable roads run off to the public water bodies. Also the coefficient of runoff from roads is high with a fast velocity of runoff, which ends up with consequence that a lot of pollutants runoff happens when it is raining. Therefore it is very important project to evaluate the quantity of pollutant loads. In this study, I computed the pollutant loadings depending on time and rainfall to analyze characteristics of runoff while first flush storm water and evaluated the runoff time while first flush storm water and rainfall based on the change in curves on the graph. I also computed contribution ratio to identify its impact on water quality of stream. I realized that the management and treatment of first flush storm water effluents is very important for the management of road's non-point source pollutants because runoff loads of non-point source pollution are over the 80% of whole loads of stream. Also according to the evaluation of runoff loads of first flush storm water for SS, run off time was shown under the 30 minute and rainfall was shown under the 5mm which is less than 20% of whole rainfall. These are under 5mm which is regarded amount of first flush storm water by the Ministry of Environment and it is judged to be because run off by rainfall is very fast on impermeable roads. Also, run off time and rainfall of BOD is higher than SS. Therefore I realized that the management of non-point source should be managed and done differently depending on each material. Finally, the contribution ratio of pollutants loads by rainfall-runoff was shown SS 12.7%, BOD 12.7%, COD 15.9%, T-N 4.9%, T-P 8.9%, however, the pollutants loads flowing into the steam was shown 4.4%. This represents that the concentration of non-point pollutants is relatively higher and we should find the methodical management and should be concerned about non-point source for improvement on water quality of streams.

• Journal of Environmental Science International
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• v.15 no.4
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• pp.359-364
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• 2006

Two sites with different average daily traffic volume at an intersection were selected in order to investigate water quality of the first flushes in the surface runoffs. The effects of rainfall intensities and accumulated non-rainy days before rainfall events on the water quality were also delineated. Samples were collected at every 2 min. interval from each first flush from February to May, 2004 for 4 major rainfall events. $COD_{cr}$ or SS concentrations at the site with an average daily traffic volume (ADTV) of 23,000 vehicles were 2-7 times higher than those at the site with an ADTV of 1,400 vehicles. The longer the accumulated non-rainy days were, the higher the concentration of heavy metals were than those of $COD_{cr}$ and SS in the first flushes.

• Journal of Korean Society on Water Environment
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• v.22 no.2
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• pp.314-320
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• 2006

Diffuse pollution from an urban area contributes to the significant pollution loading to a receiving water body. In this paper, rainfall runoffs from an urban basin with combined sewer systems located in the city of Daejeon were monitored to measure the rainfall runoff discharge rates and pollutant concentrations. Strong first flush effects were observed for all monitored rainfall runoffs. The first flush effects were closely related to rainfall intensity, while suspended solids were closely related to pollutant constituents. The observed averaged Event Mean Concentrations (EMCs) of Combined Sewer Overflows (CSOs) were 536.1 mg SS/L, 467.7 mg CODcr/L, 142.7 mg BOD/L, 16.5 mg TN/L, and 13.5 mg TP/L. Storage volumes for containing the first flush to improve water quality of the receiving stream can be estimated based on suspended solid concentration. In this study, retainment of the first flush equivalent to 5mm of precipitation could reduce diffuse pollution loading induced by CSOs to a receiving water body by up to 80% of suspended solid loading.

• Journal of Korean Society on Water Environment
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• v.27 no.5
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• pp.654-660
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• 2011

One of the best way to control Combined Sewer Overflow (CSO) is proposed to construct first flush storage tank. But there is little known parameters for optimum design of these facilities. This study was conducted to get optimum design parameters for a first flush storage tank construction. The optimization of the tank is generally based upon some measure of SS(Suspended Solid) mass holding efficiency. Water quality deterioration of receiving water body happened right after first time occurring rainfall in dry weather seasons. So, design rainfall intensity is used at 2 mm/hr for peak of monthly average intensities of dry seasons. The capacities for each evaluated catchment are designed from 14.4 min to 16.1 min HRT of CSOs flow at design rainfall intensity. Owing to all storage tanks are connected to interception sewer having a redundancy, the suggested volume could be cut down.

• Current Research on Agriculture and Life Sciences
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• v.2
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• pp.77-90
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• 1984

Results investigated backwater phenomena at Geumho river basin to get a basic data for Daegu basin area development plan are as the follows. 1. It is a A=0.35 L 1.848 (r = 0.97), the relationship between basin area and river length at Geumho river. 2. Dividing the rainfall of Geumho river basin as two parts, a first half rainfall and a second half rainfall, the amount of a first half rainfall appeared 57.5% comparison with total rainfall. 3. The maximum flood discharge appeared 12 hrs. continuous rainfall rather than 24 hrs. continuous rainfall. 4. Results investigated backwater phenomena from Geumho II bridge to chungchun appeared the rising water level of 69 cm, 55 cm, 44 cm, at section III in the starting point water level of 1.8 m, 2.4 m, 4.0 m respectively. 5. Results investigated backwater phenomena by the flood water level appeared a similar form. There was a average rising water level of 30 cm at section III. At the results of this computation, it was confirmed that section III was affected the highest backwater phenomena among the observed river reaches in Geumho river. In addition, this paper should be given a assistance to decide a economic and safe section in construction of bank of river and estuary barrage.

• Journal of The Korean Society of Agricultural Engineers
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• v.59 no.6
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• pp.73-80
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• 2017

The objective of this study is to investigate whether the daily rainfall depth derived from daily data represents the event rainfall depth derived from hourly data. For analysis, the 85th, 90th, and 95th percentile daily rainfall depths were first computed using daily rainfall data (1986~2015) collected at 63 weather stations. In addition, the storm event was separated by the interevent time definition (IETD) of 6, 12, 18, and 24 hr using hourly rainfall data. Based on the separated storm events, the 85th, 90th, and 95th percentile event rainfall depths were calculated and compared with the using hourly rainfall data with the 85th, 90th, and 95th percentile daily rainfall depths. The event rainfall depths computed using the IETD were greater than the daily rainfall depths. The difference between the event rainfall depth and the daily rainfall depth affects the design and size of the facility for controlling the stormwater. Therefore, the designer and policy decision-maker in designing the stormwater best management practices need to take into account the difference generated by the difference of the used rainfall data and the selected IETD.