• Journal of Korean Society on Water Environment
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• v.26 no.3
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• pp.507-517
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• 2010

Long-term monitoring was conducted to identify the runoff characteristics of non-point source according to the three forest types (deciduous forest, coniferous forest and mixed forest) in this study. Rainfall events of each deciduous forest, coniferous forest, and mixed forest were 10, 8, 12, respectively. Average runoff depth and coefficients of each forest type were founded to be coniferous forest and were followed by others in turns : deciduous forest, and mixed forest because various conditions (i.e., rainfall property, Antecedent Precipitation Index (API), soil property, slope, and forest management) could change runoff characteristics. In the analysis of the first flush phenomenon, it showed that SS and T-P were sensitive for the first flush phenomenon. The first flush phenomenon of them were showed differently by rainfall intensity, rainfall duration, and amount of rainfall. The research results indicated that range of the Event Mean Concentration (EMC) values in deciduous forest were 0.8~2.4 mg/L for $BOD_5$, 2.0~13.4 mg/L for $COD_{Mn}$, 1.3~2.9 mg/L for DOC, 1.150~3.913 mg/L for T-N, 0.010~0.350 mg/L for T-P and 3.1~291.8 mg/L for SS and in coniferous forest were 0.8~2.2 mg/L for $BOD_5$, 1.9~3.6 mg/L for $COD_{Mn}$, 1.0~2.0 mg/L for DOC, 1.025~2.957 mg/L for T-N, 0.002~0.084 mg/L for T-P and 0.8~5.4 mg/L for SS. Also, range of the EMC values in mixed forest were 1.3~2.3 mg/L for $BOD_5$, 2.4~4.8 mg/L for $COD_{Mn}$, 1.1~2.1 mg/L for DOC, 0.385~2.703 mg/L for T-N, 0.016~0.080 mg/L for T-P and 2.3~30.0 mg/L for SS.

• Journal of Korea Water Resources Association
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• v.46 no.9
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• pp.921-932
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• 2013

Runoff data availability is a substantial factor for precise flood control such as flood frequency or flood forecasting. However, runoff depths and/or peak discharges for small watersheds are rarely measured which are necessary components for hydrological analysis. To compensate for this discrepancy, a lumped concept such as a Storage Function Method (SFM) was applied for the partitioned Choongju Dam Watershed in Korea. This area was divided into 22 small watersheds for measuring the capability of spatial extension of runoff data. The chosen total number of flood events for searching parameters of SFM was 21 from 1991 to 2009. The parameters for 22 small watersheds consist of physical property based (storage coefficient: k, storage exponent: p, lag time: $T_l$) and flood event based parameters (primary runoff ratio: $f_1$, saturated rainfall: $R_{sa}$). Saturated rainfall and base flow from event based parameters were explored with respect to inflow at Choongju Dam while other parameters for each small watershed were fixed. When inflow of Choongju Dam was optimized, Youngchoon and Panwoon stations obtained average of Nash-Sutcliffe Efficiency (NSE) were 0.67 and 0.52, respectively, which are in the satisfaction condition (NSE > 0.5) for model evaluation. This result is showing the possibility of spatial data extension using a lumped concept model.

• Journal of Korea Water Resources Association
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• v.48 no.11
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• pp.925-936
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• 2015

The purpose of this study is to explore the effectiveness of dual-polarization radar rainfall by comapring with the flood inundation record map through KIMSTORM(Grid-based KIneMatic wave STOrm Runoff Model). For Namgang dam ($2,293km^2$) watershed, the Bisl dual-polarization radar data for 3 typhoons (Khanun, Bolaven, Sanba) and 1 heavy rain event in 2012 were prepared. For both 28 ground rainfall data and radar rainfall data, the model was calibrated using observed discharge data at 5 stations with $R^2$, Nash and Sutcliffe Model Efficiency (ME) and Volume Conservation Index (VCI). The calibration results of $R^2$, ME and VCI were 0.85, 0.78 and 1.09 for ground rainfall and 0.85, 0.79, and 1.04 for radar rainfall respectively. The flood inundation record areas (SY and MD/SG district) by typhoon Sanba were compared with the distributed modeling results. The spatial distribution by radar rainfall produced more surface runoff from the watershed and simulated higher stream discharge than the ground rainfall condition in both SY and MD/SG district. In case of MD/SG district, the stream water level by radar rainfall near the flood inundation area showed 0.72 m higher than the water level by ground rainfall.

• Journal of Korea Water Resources Association
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• v.47 no.3
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• pp.257-267
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• 2014

The impact of the combination of changes in temperature and rainfall due to climate change on surface water resources is important in hydro-meteorological research. In this study, 4 hydro-meteorological (HM) models from the Rainfall Runoff Library in the Catchment Modeling Toolkit were used to model the impact of climate change on runoff in streams for 5 river basins in the Republic of Korea. Future projections from 2021 to 2040 (2030s), 2051 to 2070 (2060s) and 2081 to 2099 (2090s), were derived from 12 General Circulation Models (GCMs) and 3 representative concentration pathways (RCPs). GCM outputs were statistically adjusted and downscaled using Long-Ashton Research Station Weather Generator (LARS-WG) and the HM models were well calibrated and verified for the period from 1999 to 2009. The study showed that there is substantial spatial, temporal and HM uncertainty in the future runoff shown by the interquartile range, range and coefficient of variation. In summary, the aggregated runoff will increase in the future by 10~24%, 7~30% and 11~30% of the respective baseline runoff for the RCP2.6, RCP4.5 and RCP8.5, respectively. This study presents a method to model future stream-flow taking into account the HM model and climate based uncertainty.

• Magazine of the Korean Society of Agricultural Engineers
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• v.8 no.1
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• pp.1011-1034
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• 1966

This thesis is the final report which has long been studied by the author to obtain the design basis for various hydrological constructions with the specific system suitable to the natural environmental conditions in Korea. This report is divided into two parts: one is to estimate runoff volume from watersheds and the other to estimate the peak discharge for a single storm. According to the result of observed runoff record from watersheds, it is known that Kajiyama formula is useful instrument in estimating runoff volume from watersheds in this country. But it has been found that this formula shows us 20-30% less than the actual flow. Therefore, when wihed to bring a better result, the watershed characteristics coefficient in this formula, that is, f-value, should be corrected to 0.5-0.8. As for the method to estimate peak discharge from drainage basin, the author proposes to classify it in two ways; one is small size watershed and the other large size watershed. The maximum -flood discharge rate $Q_p$ and time to peak Pt obtained from the observed record on the small size watershed are compared by various methods and formulas which are based upon the modern hydrological knowledge. But it was fou.d that it. was not a satisfied result. Therefore, the author proposes. tocomputate $Q_p$, to present 4.0-5.0% for the total runoff volume ${\Sigma}Q$.${\Sigma}Q$ is computed under the assumption of 30mm 103s in watershed per day and to change the theoritical total flow volume to one hour dura tion total flow rate when design daily storm is given. Time to peak Pt is derived from three parameters which are u,w,k. These are computed by relationship between total runoff volume (ha-m unit)and $Q_p$. (C.M.S. unit). Finally, the author checked out these results obtained from 51 hydrographs and got a satisfied result. Therefore the author suggested the model of design dimensionless unit-hydrograph. And the author believes that this model will be much available at none runoff record river site. In the large size watersheds in Korea when the maximum discharge occurs, the effective rainfall is two consequtive stormy days. So the loss in watershed was assutned as 6Omm/2days,and the author proposed 3-hour-daration hydrograph flow distribution percentage. This distribution percentage will be sure to form the hydrograph coordinate.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2002.10a
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• pp.461-464
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• 2002

This study is to application the TANK modle for Ponding depth and discharge, T-N, T-P simulation from paddy field area. Simulation coefficient of correlation for Ponding depth and discharge, T-N, T-P were 0.89, 0.60, 0.99, 0.91 respectively. advanced purposes are development of agriculture runoff character modeling and application of best management practice with this study model.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2003.10a
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• pp.447-450
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• 2003

It is important to calculate runoff, percolation and evapotranspiration in process hydrological cycle. Especially, a evaportranspiration in watershed has a very important effect on hydrological cycle. In the study, the watershed evapotranspiration was calculated by the water balance and a daily evaportanspiration coefficient(CE) was calculated by the modified Beken's formula.

• Journal of Environmental Science International
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• v.23 no.4
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• pp.533-541
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• 2014

The streams in Jeju Island have very distinctive hydrological and geological properties and there are a lot of limits in applying the general flood estimation method. This study presented parameters dominant in the Hancheon stream of Jeju Island by analyzing the sensitivity of parameters of HEC-HMS model regarding rainfall events in the target basin, and extracted the optimal parameter(Time of Concentration of Clark Unit Hydrograph: Kraven II method, Storage Coefficient: Sabol method) by analyzing and comparing it with the flood runoff data observed in the site and Jeju Island's observation data.

• Journal of The Korean Society of Agricultural Engineers
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• v.59 no.2
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• pp.69-79
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• 2017

In this study, we developed real-time urban stream discharge forecasting model using short-term rainfall forecasts data simulated by a regional climate model (RCM). The National Centers for Environmental Prediction (NCEP) Climate Forecasting System (CFS) data was used as a boundary condition for the RCM, namely the Global/Regional Integrated Model System(GRIMs)-Regional Model Program (RMP). In addition, we make ensemble (ESB) forecast with different lead time from 1-day to 3-day and its accuracy was validated through temporal correlation coefficient (TCC). The simulated rainfall is compared to observed data, which are automatic weather stations (AWS) data and Tropical Rainfall Measuring Mission (TRMM) Multisatellite Precipitation Analysis (TMPA 3B43; 3 hourly rainfall with $0.25^{\circ}{\times}0.25^{\circ}$ resolution) data over midland of Korea in July 26-29, 2011. Moreover, we evaluated urban rainfall-runoff relationship using Storm Water Management Model (SWMM). Several statistical measures (e.g., percent error of peak, precent error of volume, and time of peak) are used to validate the rainfall-runoff model's performance. The correlation coefficient (CC) and the Nash-Sutcliffe efficiency (NSE) are evaluated. The result shows that the high correlation was lead time (LT) 33-hour, LT 27-hour, and ESB forecasts, and the NSE shows positive values in LT 33-hour, and ESB forecasts. Through this study, it can be expected to utilizing the real-time urban flood alert using short-term weather forecast.

• Journal of Korean Society on Water Environment
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• v.24 no.1
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• pp.69-77
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• 2008

This study was conducted to know the characteristics of agricultural non-point source pollutants runoff by rainfall events at the upper catchment of Goseong reservoir in Gonjy city, Chungnam Province. For this study, the monitoring sites of the research catchment were set nineteen during the research period (between June 2005 and October 2006). Average runoff coefficient were observed 0.51 in 2005, 0.71 in 2006, respectively. The correlation coefficient (r) between the rainfall and peak-flow was investigated 0.787. By rainfall events, the water quality of the sites were shown like this : BOD 0.555~9.60 mg/L, T-N 0.01~13.50 mg/L, T-P 0.002~2.952 mg/L, and SS N.D~820.0 mg/L. The strong rainfall intensity was the most important factor of the soil erosion. The gabs of the arithmetic mean concentrations and the flow weighted mean concentrations were observed as the followings : BOD 0.0~29.2%, T-N 0.1~11.4%, T-P 0.4~95.2%, and SS 1.7~57.0% in 2005, and BOD 1.0~11.9%, T-N 0.7~7.3%, T-P 9.9~36.5%, and SS 6.6~36.5% in 2006, respectively. The BOD pollution load was 2,117 kg (36% of the total BOD loading of survey periods) while, T-N was 3,209.0 kg (27.9% of the total T-N loading of survey periods), T-P was 136.4 kg (37.4% of the total T-P loading of survey periods) and SS was 72,733.8 kg (51.8% of the total SS loading of survey periods) in the year 2005. In case of 2006, BOD load was 1,321.7, T-N was 2,845.8, T-P was 42.9, and SS was 16,275.8 kg, respectively.