• Journal of the Korean Association of Geographic Information Studies
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• v.14 no.3
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• pp.36-51
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• 2011

Global climate change is disturbing the water circulation balance by changing rates of precipitation, recharge and discharge, and evapotranspiration. Groundwater, which occupies a considerable portion of the world's water resources, is related to climate change via surface water such as rivers, lakes, and marshes. In this study, the authors selected a relevant climate change scenario, A1B from the Special Report on Emission Scenario (SRES) which is distributed at Korea Meteorological Administration. By using data on temperature, rainfall, soil, and land use, the groundwater recharge rate for the research area was estimated by periodically and embodied as geographic information system (GIS). In order to calculate the groundwater recharge quantity, Visual HELP3 was used as main model, and the physical properties of weather, temperature, and soil layers were used as main input data. General changes to water circulation due to climate change have already been predicted. In order to systematically solve problems of ground circulation system, it may be urgent to recalculate the groundwater recharge quantity and consequent change under future climate change. The space-time calculation of changes of the groundwater recharge quantity in the study area may serve as a foundation to present additional measures to improve domestic groundwater resource management.

• Journal of Korea Water Resources Association
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• v.44 no.2
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• pp.135-144
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• 2011

Direct parameter estimation method is verified with various models based on Neyman-Scott rectangular pulse model (NSRPM). Also, newly modified NSRPM (NMSRPM) that uses normal distribution is developed. Precipitation data observed by Korea Meteorological Administration (KMA) for 47 years is applied for parameter estimation. For model performance verification, we used statistics, wet ratio and precipitation accumulate distribution of precipitation generated. The comparison of statistics indicates that absolute relative error (ARE)s of the results from NSRPM and modified NSRPM (MNSRPM) are increasing on July, August, and September and ARE of NMNSRPM shows 10.11% that is the smallest ARE among the three models. NMNSRPM simulates the characteristics of precipitation statistics well. By comparing the wet ratio, MNSRPM shows the smallest ARE that is 16.35% and by using the graphical analysis, we found that these three models underestimate the wet ratio. The three models show about 2% of ARE of precipitation accumulate probability. Those results show that the three models simulate precipitation accumulate probability well. As the results, it is found that the parameters of NSRPM, MNSRPM and NMNSRPM are able to be estimated by the direct parameter estimation method. From the results listed above, we concluded that the direct parameter estimation is able to be applied to various models based on NSRPM. NMNSRPM shows good performance compared with developed model-NSRPM and MNSRPM and the models based on NSRPM can be developed by the direct parameter estimation method.

• Current Research on Agriculture and Life Sciences
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• v.7
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• pp.55-66
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• 1989

The purpose of this study is to estimate the flood discharge and peak time by the SCS method and the probability method using the geomorpologic parameters obtained from the topographic maps following the law of stream classifying and, ordering by Horton and Strahler. The SCS method and the probability method are used in estimating the times to peak and the flood discharges at An-dong, Im-ha, and Sun-san basins in the Nakdong River system. The results obtained are as follows : 1. The range of the values of the area ratio, the bifurcation ratio and the length ratio agree with those of natural streams presented by Horton and Strahler. 2. Comparisons of the probability method and observed values show that small relative errors of 0-7% of flood discharge, and 0-2hr, difference in time to peak respectivly. But the SCS method shows that large relative errors of 10-40% of flood discharge, and 0-4hr, difference in time to peak. 3. When the rainfall intensity is large, the error of flood discharge estimated by using the probability method is relativly small.

• Journal of the Korean Society for Marine Environment & Energy
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• v.3 no.4
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• pp.76-90
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• 2000

The estimation of material cycle of pollutants is necessary for the environment management in coastal zone. Model for material budgets are useful tools to understand the phenomena of natural system and to provide an insight into the complex processes including physical, chemical and biological processes occuring in natural system. Budgets of fresh water, salt and nutrients were estimated in order to clarify the characteristics of seasonal material cycle in Keum river estuary. Inflow volumes of freshwater into system was approximately 1.014×10/sup 8/～12.565×10/sup 8/m³/month and discharge in Keum river has occupied 99.7% of total freshwater. Seasonal variations of freshwater volume in the system were found to be very high in the range of about 4 ～ 14 times due to rainfall in summer season. Existing water mass of freshwater in system calculated by salt budget was approximately 0.339×10/sup 8/～0.652×10/sup 8/m³. Mean residence time of freshwater was calculated to be about 1.6～10.0day, and exchange time was calculated to be about 2.2～11.9day. Mean residence time was short as 1.6day in summer due to precipitation, and long as 10.1day in winter due to a drought. Inflow masses of DIP and DIN were approximately 5.57～32.68ton/month and 234.93～2,373.39ton/month, respectively. Seasonal inflow mass of DIP was larger than the outflow mass except for summer season. Thus, we postulate that accumulation of DIP in the system will happen. Residence times of DIP and DIN were calculated to be 1.1～6.4day and 1.8～10.9day, respectively. The ratio of water residence time versus DIP, DIN residence time was calculated to be 0.39～2.31 times and 0.83～1.13 times, respectively.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.7
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• pp.337-342
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• 2018

A rain water pumping station is a structural countermeasure to inland flooding of domestic water generated in a urban watershed. In this study, the optimal operation water level of the pump with the minimum overflow was determined based on the opinions of the person in charge of the operation of the rain water pump station. A GA (Genetic Algorithm), which is an optimization technique, was used to estimate the optimal operation water level of the rain water pump station and was linked with SWMM (Ver.5.1) DLL, which is a rainfall-runoff model of an urban watershed. Considering the time required to maximize the efficiency of the pump, the optimal operating water level was estimated. As a result, the overall water level decreased at a lower operating water level than the existing water level. For most pumps, the lowest operating water level was selected for the operating range of each pump unit. The operation of the initial pump could reduce the amount of overflow, and there was no change in the overflow reduction, even after changing the operation condition of the pump. Internal water flooding reduction was calculated to be 1%~2%, and the overflow occurring in the downstream area was reduced. The operating point of the pump was judged to be an effective operation from a mechanical and practical point of view. A consideration of the operating conditions of the pump in future, will be helpful for improving the efficiency of the pump and to reducing inland flooding.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.5
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• pp.1009-1019
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• 2009

In this research, various characteristics of South Korea's design flood have been examined by deriving appropriate design flood, using data obtained from careful observation of actual floods occurring in selected main watersheds of the nation. 19 watersheds were selected for research in Korea. The various characteristics of annual rainfall were analyzed by using a moving average method. The frequency analysis was decided to be performed on the annual maximum flood of succeeding one year as a reference year. For the 19 watersheds, tests of basic statistics, independent, homogeneity, and outlier were calculated per period of annual maximum flood series. By performing a test using the LH-moment ratio diagram and the Kolmogorov-Smirnov (K-S) test, among applied distributions of Gumbel (GUM), Generalized Extreme Value (GEV), Generalized Logistic (GLO) and Generalized Pareto (GPA) distribution was found to be adequate compared with other probability distributions. Parameters of GEV distribution were estimated by L, L1, L2, L3 and L4-moment method based on the change in the order of probability weighted moments. Design floods per watershed and the periods of annual maximum flood series were derived by GEV distribution. According to the result of the analysis performed by using variation rate used in this research, it has been concluded that the time for changing the design conditions to ensure the proper hydraulic structure that considers recent climate changes of the nation brought about by global warming should be around the year 2002.

• Journal of Korea Water Resources Association
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• v.39 no.7 s.168
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• pp.593-603
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• 2006

The basin response to storm is regarded as nonlinearity inherently. In addition, the consistent nonlinearity of hydrologic system response to rainfall has been very tough and cumbersome to be treated analytically. The thing is that such nonlinear models have been avoided because of computational difficulties in identifying the model parameters from recorded data. The parameters of nonlinear system considered as dynamic effects in the conceptual model are optimized as the sum of errors between the observed and computed runoff is minimized. For obtaining the optimal parameters of functions, the historical data for the Bocheong watershed in the Geum river basin were tested by applying the numerical methods, such as quasi-linearization technique, Runge-Kutta procedure, and pattern-search method. The estimated runoff carried through from the storage function with dynamic effects was compared with the one of 1st-order differential equation model expressing just nonlinearity, and also done with Nash model. It was found that the 2nd-order model yields a better prediction of the hydrograph from each storm than the 1st-order model. However, the 2nd-order model was shown to be equivalent to Nash model when it comes to results. As a result, the parameters of nonlinear 2nd-order differential equation model performed from the present study provided not only a considerable physical meaning but also a applicability to Korean watersheds.

• Journal of Wetlands Research
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• v.18 no.2
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• pp.183-193
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• 2016

In this study, design and performance of infiltration trench using woodchip as media for treating stormwater from highway were examined through field monitoring. Average reduction efficiency for TSS, COD, BOD, TN, and TP was 88%, 94%, 85%, 80%, and 75% respectively, which is similar to values reported by other studies and design manuals even though direct comparison is not possible due to different monitoring and design conditions. Mean field infiltration rate estimated by measuring the change of water depth inside the observation well was about 40mm/hr, and the time taken for complete infiltration was about 0.83days, which corresponds well with design criteria recommended by MOE guidelines in Korea. In addition, according to analysis of infiltration rate and reduction efficiency, effective rainfall depth applied for determining water quality volume(WQv), 5mm was found to be properly established as design criteria. Woodchip must be considered and included as an alternative media together with crushed rock and gravel into the design guidelines because it has more advantages in terms of weight, porosity, cost, and easiness of management than other media materials.

• Journal of the Korean Association of Geographic Information Studies
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• v.10 no.3
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• pp.58-69
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• 2007

The vegetation area that occupies 76% in land surface of the earth can give a considerable impact on water resources, environment and ecological system by future climate change. The purpose of this study is to predict future vegetation cover information from NDVI (Normalized Difference Vegetation Index) extracted from satellite images. Current vegetation information was prepared from monthly NDVI (March to November) extracted from NOAA AVHRR (1994 - 2004) and Terra MODIS (2000 - 2004) satellite images. The NDVI values of MODIS for 5 years were 20% higher than those of NOAA. The interrelation between NDVIs and monthly averaged climate factors (daily mean, maximum and minimum temperature, rainfall, sunshine hour, wind velocity, and relative humidity) for 5 river basins of South Korea showed that the monthly NDVIs had high relationship with monthly averaged temperature. By linear regression, the future NDVIs were estimated using the future mean temperature of CCCma CGCM2 A2 and B2 climate change scenario. The future vegetation information by NOAA NDVI showed little difference in peak value of NDVI, but the peak time was shifted from July to August and maintained high NDVIs to October while the present NDVI decrease from September. The future MODIS NDVIs showed about 5% increase comparing with the present NDVIs from July to August.

• Journal of the Korean Association of Geographic Information Studies
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• v.21 no.3
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• pp.48-62
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• 2018

In this study, landslide of debris flow occurred at 51 sites around Daeryounsan located in between Chuncheon-si and Hongcheon-gun during July in 2013 were investigated in field and behavior characteristics of debris flow were analyzed on the basis of records of rainfall and site investigation. According to debris flow types of channelized and hill slope, location and slope angle of initiation and deposit zone, and width and depth of erosion were investigated along entire runout of debris flow. DEM(Digital Elevation Model) of Daeryounsan was constructed with digital map of 1:5,000 scale. Land slide hazard was estimated using SINMAP(Stability INdex MAPping) and the predicted results were compared with field sites where debris flow occurred. As analyzed results, for hill slope type of debris flow, predicted sites were quite comparable to actual sites. On the other hand, for channelized type of debris flow, debris flow occurrence sites were predicted by using stability index associated with topographic wetness index. As analyzed results of 4 different conditions with the parameter T/R, Hydraulic transmissivity/Effective recharge rate, proposed by NRCS (Natual Resources Conservation Service), predicted results showed more or less different actual sites and the degree of hazard tended to increase with decrease of T/R value.