• Journal of Environmental Impact Assessment
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• v.31 no.1
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• pp.1-10
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• 2022

This study was carried out to understand the water quality characteristics of the initial stormwater runoff and the origin of soluble pollutants according to various rainfall conditions from a non-point source reducing facility. The water sample from this study was collected among 10 collection facilities in the G-drainage area. Specifically, five of the collection points including #1, #5, #8, #9, and #10 were reported with unknown water inflow even during non-rain conditions. The leakage characteristics of non-point pollutants from the collection facilities were then able to identify accordingly. The water quality characteristics of the stormwater runoff from the collection facilities were strongly affected by the amounts of rainfalls. The average concentrations of EC, BOD, TOC, and TN during non-rain were found to be higher than their concentrations during rain; on the other hand, the average concentrations of DO were found to be lower than its concentrations during rain. In addition, the distribution of organic components existing in the effluent of collection facilities were identified based on the dissolved organic matter analysis. In summary, the stormwater runoff was highly affected by pollutants flowing from the surrounding environment, and the amounts of hard-to-decompose humic substances were greatly increased in the collection facilities due to rain.

• Journal of Environmental Science International
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• v.22 no.5
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• pp.523-531
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• 2013

In this study, a method of simulating ephemeral stream runoff characteristics in Jeju watershed is newly suggested. The process based conceptual-physical scheme is established based on the SWAT-K and applied to Cheonmi-cheon watershed which shows the typical pattern of ephemeral stream runoff characteristics. For the proper simulation of this runoff, the intermediate flow and baseflow are controlled to make downward percolation should be dominant. The result showed that surface runoff simulated by using the modified scheme showed good agreement with observed runoff data. In addition, it was found that the estimated runoff directly affected the groundwater recharge rate. This conceptual model should be continuously progressed including rainfall interception, spatially estimated evapotranspiration and so forth for the reasonable simulation of the hydrologic characteristics in Jeju island.

• Journal of Korean Society of Forest Science
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• v.87 no.1
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• pp.11-19
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• 1998

The purpose of this study was to develop the Rainfall-Runoff Model for a long and short term runoff analysis in small forested mountain watersheds. This model was derived from tank model. This model is composed of four tank. Tank I, Tank II, TankIII, and TankIV represent interception loss in forest canopy, direct runoff, base flow, and surface flow component, respectively. This model was tested with two experimental watersheds, located in southern part of Korea. As the result, this model had potentials for simulating and analyzing the long and short term runoff in small forested watersheds.

• Journal of Radiation Protection and Research
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• v.27 no.3
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• pp.165-170
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• 2002

Combined with deposition model onto the ground of radionuclides, the influence of radioactive contamination to agricultural products was analyzed due to wet deposition as well as dry deposition from radioactive air concentration during a nuclear emergency. The previous dynamic food chain model, in which initial input parameter is only radionuclide concentrations on the ground, was improved for the evaluating of radioactive contamination to agricultural products from either radionuclide concentrations in air or radionuclide concentrations on the ground. As the results, in case of deposition onto the ground, wet deposition was more dominant process than thy deposition. While the contamination levels of agricultural products were dependent on the a variety of factors such as radionuclides and rainfall rate. It means that the contamination levels of agricultural products are determined from which is more dominant process between deposition on the ground and interception onto agricultural plants.

• Journal of Korean Society on Water Environment
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• v.23 no.4
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• pp.527-534
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• 2007

To operate scientifical and integrated management of water resources, it needs to identify clearly the quantitative variation and moving pathway of water resources in a basin. Moreover, it needs to also estimate more precisely the amount of runoff generating from the precipitation. Thus, in this study, to carry out more reliable hydrologic analyses, the runoff characteristics according to detailed runoff components and water balance in a basin are analyzed. As a result of yearly water balance analyses, during the period of drought year, the loss is bigger than that of 6-year mean loss and the return flow of groundwater is the most dominant component of runoff. During the period of flood year, the loss is smaller about 4% than that of 6-year mean loss and the subsurface water is the most dominant component of runoff. The loss due to the interception and evapotranspiration for 6-year mean loss is about 53% of the total rainfall, the mean runoff ratio is about 27% and the baseflow is about 22%.

• Korean Journal of Agricultural Science
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• v.48 no.3
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• pp.629-642
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• 2021

Land-use change has an important role in the hydrologic characteristics of watersheds because it alters various hydrologic components such as interception, infiltration, and evapotranspiration. For example, rapid urbanization in a watershed reduces infiltration rates and increases peak flow which lead to changes in the hydrologic responses. In this study, a physical hydrologic model the soil and water assessment tool (SWAT) was used to assess long-term continuous daily streamflow corresponding to land-use changes that occurred in the Naesungchun river watershed. For a 30-year model simulation, 3 different land-use maps of the 1990s, 2000s, and 2010s were used to identify the impacts of the land-use changes. Using SWAT-CUP (calibration and uncertainty program), an automated parameter calibration tool, 23 parameters were selected, optimized and compared with the daily streamflow data observed at the upstream, midstream and downstream locations of the watershed. The statistical indexes used for the model calibration and validation show that the model performance is improved at the downstream location of the Naesungchun river. The simulated streamflow in the mainstream considering land-use change increases up to -2 - 30 cm compared with the results simulated with the single land-use map. However, the difference was not significant in the tributaries with or without the impact of land-use change.

• Proceedings of the Korea Water Resources Association Conference
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• 2002.05b
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• pp.1034-1040
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• 2002

A rainwater recharge model, which is combined with the quasi-three dimensional unconfined groundwater flow, is proposed in the present paper. The water budget in the catchments of the planned new campus of Kyushu University is evaluated by the present method that calculates both the surface runoff and groundwater flow simultaneously. The results obtained in the present study reveal that the calculated monthly and annual runoff discharges agree reasonably well with the observed discharge. Combining the rainwater recharge model, the two-phase groundwater flow equation is numerically solved f3r the entire area including the low land where the salt water intrusion is observed. The calculated depth of the salt-fresh interface agrees reasonably well with the observed ones at several cross sections. On the other hand, however, it is found that the calculated water budget remains uncertain because of lack of information on the accurate potential evapotranspiration including rainfall interception. In conclusion, however, it is found that the proposed method is applicable for the areas where the horizontal flow is dominant and the interface is assumed to be sharp.

• Korean Journal of Agricultural and Forest Meteorology
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• v.8 no.3
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• pp.174-182
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• 2006

This study was to clarify the effects of forest stand changes on hydrological components of evapotranspiration and discharge. The forest-hydrological experimental stations in Gwangneung and Yangju, Gyeonggido near metropolitan Seoul have been operated by the Korea Forest Research Institute since 1979 to clarify the effects of forest types and practices on the water resources and nutrient cycling and soil loss. The hydrological regime of the forested catchments may change as forests develop. The ranges of change may be different depending on forest types. Evapotranspiration can be estimated to 679mm, 580mm and 368mm in planted young coniferous (PYC), natural old-growth deciduous (NOD) and rehabilitated young mixed (RYM), respectively. The slope of the discharge-duration curve shows the capacity of discharge control in a specific catchment. The slope tended to be steeper in RYM than NOD, the better forest condition. The slope in RYM became more gentle as the forest stand developed. Forests can modulate peak flows through interception, evapotranspiration and soil storage opportunity. PYC and RYM showed 100 and 50mm of threshold rainfall for modulating peak flows, respectively. The deciduous forest did not represent sudden changes of peak flow rates to rainfall, even 200 mm rainfall Forest development in PYC may play an important role in modulation of peak flows because peak flow rates reduced after 10 years.

• Korean Journal of Environmental Biology
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• v.32 no.4
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• pp.389-394
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• 2014

This study was conducted to find out the soil $CO_2$ emission characteristic due to rain fall pattern and intensity changes. Using Automatic Opening and Closing Chambers (AOCCs), we have measured annual soil respiration changes in Pinus koraiensis plantation at Seoul National University experimental forest in Mt. Taehwa. In addition, we have monitored heterotrophic respiration at trenching sites ($4{\times}6m$). Based on the one year data of soil respiration and heterotrophic respiration, we observed that 24% of soil respiration was derived from root respiration. During the rainy season (end of July to September), soil respiration at trenching site and trenching with rainfall interception site were measure during portable soil respiration analyzer (GMP343, Vaisala, Helsinki, Finland). Surprisingly, even after days of continuous heavy rain, soil water content did not exceed 20%. Based on this observation, we suggest that the maximum water holding capacity is about 20%, and relatively lower soil water contents during the dry season affect the vital degree of trees and soil microbe. As for soil respiration under different rain intensity, it was increased about 14.4% under 10 mm precipitation. But the high-intensity rain condition, such as more than 10 mm precipitation, caused the decrease of soil respiration up to 25.5%. Taken together, this study suggests that the pattern of soil respiration can be regulated by not only soil temperature but also due to the rain fall intensity.

• Journal of Korean Society on Water Environment
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• v.22 no.6
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• pp.982-990
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• 2006

Generally CSOs (Combined Sewer Overflows) are regarded as one of the most serious nonpoint pollution source in the urban watershed, Particularly, the water quality of the Oncheon stream is seriously affected by CSOs because the capacity of interception sewer system connected to the Suyoung wastewater treatment plant is too small to intercept most storm water discharges. The objective of this study is to evaluate the effect of nonpoint source on an urban stream with regards to combined sewer system and separate sewer system using GIS (Geographic Information System) and SWMM (Storm Water Management Model), and to provide an insight for the management of urban stream water quality. In order to consider the effect of CSOs on the receiving water quality, the flow divider element in SWMM was applied. The model calibration and verification were performed by the measured data of quantity and quality on the Oncheon stream. The quantity data acquired from the Suyoung wastewater treatment plant were also used for this procedure. In case of separate sewer system, the modeling results showed the increased tendency in streamflow compared with the combined system in dry weather, In addition, the water quality is remarkably improved in rainfall events at the separate condition. The results imply that the construction of separate sewer system should be taken into first consideration to restore the quality and quantity of water in urban streams.