• Proceedings of the Korea Water Resources Association Conference
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• 2011.05a
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• pp.16-16
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• 2011

Statistics of extreme rainfall play a vital role in engineering practice from the perspective of mitigation and protection of infrastructure and human life from flooding. While flood frequency assessments, based on river flood flow data are preferred, the analysis of rainfall data is often more convenient due to the finer spatial nature of rainfall recording networks, often with longer records, and potentially more easily transferable from site to site. The rainfall frequency analysis as a design tool has developed over the years in New Zealand from Seelye's daily rainfall frequency maps in 1947 to Thompson's web based tool in 2010. This paper will present a history of the development of New Zealand rainfall frequency analysis methods, and the details of the latest method, so that comparisons may in future be made with the development of Korean methods. One of the main findings in the development of methods was new knowledge on the distribution of New Zealand rainfall extremes. The High Intensity Rainfall Design System (HIRDS.V3) method (Thompson, 2011) is based upon a regional rainfall frequency analysis with the following assumptions: $\bullet$ An "index flood" rainfall regional frequency method, using the median annual maximum rainfall as the indexing variable. $\bullet$ A regional dimensionless growth curve based on the Generalised Extreme Value (GEV), and using goodness of fit test for the GEV, Gumbel (EV1), and Generalised Logistic (GLO) distributions. $\bullet$ Mapping of median annual maximum rainfall and parameters of the regional growth curves, using thin-plate smoothing splines, a $2km\times2km$ grid, L moments statistics, 10 durations from 10 minutes to 72 hours, and a maximum Average Recurrence Interval of 100 years.

• Journal of Climate Change Research
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• v.7 no.4
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• pp.507-512
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• 2016

This study was conducted to classify agroclimatic zones in South Korea. To classify the agroclimatic zones, such climatic factors as amount of rainfall from April to May, amount of rainfall in October, monthly average air temperature in January, monthly average air temperature from April to May, monthly average air temperature from April to September, monthly average air temperature from December to March, monthly minimum air temperature in January, monthly minimum air temperature from April to May, Warmth Index were considered as major influencing factors on the crop growth. Climatic factors were computed from monthly air temperature and precipitation of climatological normal year (1981~2010) at 1 km grid cell estimated from a geospatial climate interpolation method. The agroclimatic zones using k-means cluster analysis method were classified into 6 zones.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.3B
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• pp.185-192
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• 2012

Drought vulnerability index was developed by selecting drought-related indicators with trend test. Study areas were determined by considering the weir locations from the four major rivers restoration project in Nakdong and Geum river watersheds. Ten indicators were selected and they were categorized into three groups, water resources, precipitation pattern, and social aspects. Annual average surface water level, annual minimum surface water level, annual average groundwater level, and annual minimum groundwater level data sets were collected for water resources aspects. The number of non-rainy days, rainfall concentration ratio, and rainfall deviation were considered for precipitation pattern category. The amount of water available per capita, financial soundness for water resources, and water usage equity were related to social aspects. Mann-Kendall, Hotelling-Pabst, and Sen trend tests were performed for the ten indicator data sets and the results were scored for the drought vulnerability index. The results shows Gumi, Sangjoo, and Hapcheon weirs are relatively vulnerable to drought. The indices were relatively low for the regions in Geum river watershed compared to those in Nakdong river watershed.

• Journal of Korean Society on Water Environment
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• v.36 no.1
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• pp.1-13
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• 2020

The purpose of this study was to investigate the thermal and chemical stratification in Lake Paldang 2013-2018 weekly using Schmidt's stability index (SSI) and the index of chemical stratification (IC-i). The annual average for SSI was 19.1 g cm/㎠ with the maximum value of 45.3 g cm/㎠ in the summer and the minimum value of 4.8 g cm/㎠ in fall-winter showing seasonal differences as well as increased vertical mixing in the summer. The lake stability increased higher in 2016 as compared with the other period. The most influential factors of thermal stratification were temperature and heavy rainfall. Especially, high water temperature and a prolonged residence duration caused by reduced rainfall and inflows could result in an increase of the stratification period. While decreasing inflow and outflow at the end of the rainfall, the thermal stratification was restrengthened within 7-14 days, and then stabilized rapidly before the rainfall. IC-DO increased with high air temperature in the spring and fall-winter. However increasing sunshine duration and residence time and decreasing rate of outflow caused an increase of IC-DO in the summer. Rainfall (less than 800 mm/year) and discharge (less than 200 CMS) significantly declined in 2015 resulting in IC-DO (0.77) increased more than three times over the other years and bottom water hypoxia occurred. The SSI and IC-i used in this study could be applied to other lakes to understand changes in stratification and mixing dynamics.

• Magazine of the Korean Society of Agricultural Engineers
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• v.37 no.E
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• pp.72-78
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• 1995

To support some knowledge in planning irrigation system, short or long-term irrigation scheduling or determining irrigation reservoir capacity, it is necessary to estimate peak irrigation requirements and seasonal distribution of water demands for various return periods. In this paper Dry Day Index and Probable Evapotranspiration were evaluated to decide seasonal consumptive use of paddy rice for a design year using several decades' daily rainfall data and 5 years'('82~'86) actual evapotranspiration data, respectively. To obtain Dry Day Index that is defined as the number of probable dry days for a given period, Slade unsymmetrical distribution function was adopted. Dry Day Index was analysed for 5 and 10-day intervals. Each of them was evaluated with return periods of 1, 3, 5, 10 and 20 year. Their singnificance was tested by X$^2$ method. Based on these values, the Probable Evaportanspiration, that is the average daily ET both in dry days and rainy days during a given period, was estimated. Crop coefficient was also determined by the modified Penman equation proposed by Doorenbos & Pruitt.

• The Journal of the Korea Contents Association
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• v.7 no.3
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• pp.140-151
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• 2007

In this study, we attempted to develop a watershed runoff index subject to main control points by dividing the Geum River basin into 14 sub-basins. The Yongdam multipurpose dam Daecheong multipurpose dam and Gongju gage station were selected to serve as the main control points of the Geum River basin, and the observed flow of each control point was calculated by the discharge rating curve, whereas the simulated flow was estimated using the Rainfall Runoff Forecasting System (RRFS), user-interfaced software developed by the Korea Water Corporation, based on the Streamflow Synthesis and Reservoir Regulation (SSARR) model developed by the US Army Corps of Engineers. This study consisted of the daily unit observed flow and the simulated flow of the accumulated moving average flow by daily, 5-days, 10-days, monthly, quarterly and annually, and normal monthly/annually flow. We also performed flow duration analysis for each of the accumulated moving average and the normal monthly/annually flows by unit period, and abundant flow, ordinary flow, low flow and drought flow estimated by each flow duration analysis were utilized as watershed runoff index by main control points. Further, as we determined the current flow by unit period and the normal monthly/annually flow through the drought and flood flow analysis subject to each flow we were able to develop the watershed runoff index in a system that can be used to determine the abundance and scarcity of the flow at the corresponding point.

• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.430-430
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• 2022

20년 이상의 분단위 강우자료가 없는 지역에서는 연강수량, 월강수량, 일강수량 등을 이용하여 강우가식성지표를 추정하는 연구가 이루어지고 있다. 이중에서 월강수량을 이용한 연평균 강우가식성지표 추정방법은 Fouriner Index, Modified Index, IAS index, Modified IAS index 등 학계에서 다양한 모델이 제시된 바 있다. 국내에서는 1971 ~ 1999년 기간의 기상청 관측지점에 대한 평가가 일부 이루어진 바 있으나, 월강수량을 이용한 추정모델에 대한 후속 연구는 이루어지지 않았다. 본 연구에서는 1981 ~ 2020년 기간의 기상청 강우자료를 이용하여 월강수량 기반 강우가식성지표 추정모델의 적용성을 평가하기 위한 것으로, 선행 연구에서 기산정된 지점별 연평균 강우가식성지표 값을 바탕으로, 월강수량 기반의 기존 추정모델로 산정한 값을 비교 분석하였다. 이를 바탕으로 실무에서 활용할 수 있도록 월강수량을 이용하여 연평균 강우가식성지표를 추정할 수 있는 경험식을 업데이트 하여 제안하였다.

• Journal of Environmental Science International
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• v.19 no.6
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• pp.665-670
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• 2010

Pollutants from urban pavement consists various kinds of substances which are originated from dry deposition, a grind out tire, corrosive action of rain to pavement and facilities and raw materials of the road etc.. These are major pollutants of urban NPS (Non-point source) during rainfall period. However there is not enough information to control such pollutants for appropriate management of natural water quality. In this study of transportation areas, three monitoring stations were set up at trunk road, urban highway and national road in Gyeongnam province. Runoff flow rate was measured at every 15minutes by automatic flow meters installed at the end of storm sewer pipe within the road catchment area for water quality analysis. Data was collected every 15 minutes for initial two hours of rainfall. Additional samples were collected 1-4 hours interval till the end of rainfall. The monitoring parameters were $COD_{Mn}$, SS, T-N & T-P and heavy metals. The average EMCs of TSS and $COD_{Mn}$ were 62.0 mg/L and 24.2 mg/L on the city trunk road, which were higher than those of urban highway and national road, indicating higher pollutant loads due to activities in the city downtown area beside the vehicle. On the other hand, the average EMC of T-N and T-P were in the range of 2.67-3.23 mg/L and 0.19-3.21 mg/L for all the sampling sites. Heavy metals from the roads were mainly Fe, Zn, Cu and Mn, showing variable EMCs by the type of road. From the TSS wash-off analysis in terms of FF(first flush) index, first flush phenomenon was clearly observed in the trunk road(FF : 0.89-1.43). However, such mass delivery behavior was not apparently shown in urban highway(FF : 0.90-1.11) and national road(FF : 0.81-1.41).

• Magazine of the Korean Society of Agricultural Engineers
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• v.31 no.4
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• pp.81-89
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• 1989

This study is to determine seasonal consumptive use of water of a design year during growing period (June-September) for paddy rice in Suwon. To obtain Dry flay Index which is defined as the number of probable dry days occurring at a design year, Slade Partly Un- symmetrical Distribution Function was adopted. Dry Day Index was analysed with 5, 10 and 30 day-term. And each of them was evaluated with recurrence intervals of 1, 3, 5, 10 and 20 year using 49 years daily rainfall data('35-'83). Their singnificance were tested at 1% level by X$^2$ test. On the basis of these values, Probable Evapotranspiration (ET) which is the daily average ET for the sum of both ET on dry days and ET on rainy days were esti- mated using 5 years daily actual ET data(' 82-' 86). Their Crop Coefficients were also de- termined by the modified Penman equation(1977) proposed by Doorenbos & Pruitt.

• Journal of The Korean Society of Agricultural Engineers
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• v.49 no.6
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• pp.21-33
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• 2007

Different vegetation indices from satellite images have been used for monitoring drought damages, and this study aimed to develop a drought index using NOAA/AVHRR NDVI(Normalized Difference Vegetation Index) and to analyze the temporal and spatial distribution of spring drought severity in North Korea from 1998 to 2001. A new drought index, DevNDVI(Deviation of NDVI), was defined as the difference between a monthly NDVI and average monthly NDVI at the same cover area, and the DevNDVI images at all years except for 2001 demonstrated the drought-damaged areas referred from various domestic and foreign publications. The vegetation of 2001 showed high vitality despite the least amount of rainfall among the target years, and the reason was investigated that higher temperature above normal average would shift the growing stages of plants ahead. Therefore, complementary methods like plant growth models or ground survey data should be adopted in order to evaluate drought-induced plant stress using satellite-based NDVI and to make up far the distortion induced by other environments than lack of precipitation.