• KSCE Journal of Civil and Environmental Engineering Research
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• v.8 no.1
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• pp.113-125
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• 1988

The design flood formulas in Korean river are reviewed from the early historical stage of the river improvement projects to the present situation. The 11 different formulas are selected for the comparative purpose of the each results at the same rainfall and basin characteristics under the same size of the basin. The max. and min. values of the design flood discharge for the same basin deviated almost as large as 400% according to the formula used without respect to the basin size. The remains have big scattering within those deviations. The steps to derive the design flood are very complicated and tedious time consuming process at present applications. However the reaults computed through the steps are quationable in accordance with the lengths of the hydrological historic records and the accuracy of the data observation technique in view of the engineering judgement. The purpose of this review will give the one of the simplest and the reasonable approach to eliminate misleading the determination of the design flood peak.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.5
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• pp.1861-1870
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• 2013

A climate change-driven increased hydrological variability has been widely acknowledged over the past decades. In this regards, rainfall simulation techniques are being applied in many countries to consider the increased variability. This study proposed a Homogeneous Hidden Markov Chain(HMM) designed to recognize rather complex patterns of rainfall with discrete hidden states and underlying distribution characteristics via mixture probability density function. The proposed approach was applied to Seoul and Jeonju station to verify model's performance. Statistical moments(e.g. mean, variance, skewness and kurtosis) derived by daily and seasonal rainfall were compared with observation. It was found that the proposed HMM showed better performance in terms of reproducing underlying distribution characteristics. Especially, the HMM was much better than the existing Markov Chain model in reproducing extremes. In this regard, the proposed HMM could be used to evaluate a long-term runoff and design flood as inputs.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.35 no.2
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• pp.319-326
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• 2015

Rainfall data is necessary component for water resources design and flood warning system. Most analysis are used long-term hourly data of surface synoptic stations from the Meteorological Administration, Ministry of land, Infrastructure and Transport and others. However, It will be used minutely data of more high density automatic weather stations than surface synoptic stations expecting to increase the frequency of heavy precipitation. But minutely data has a problem about quality of rainfall data by auto observation. This study analyzed about quality control method using automatic weather station's minutely rainfall data of meteorological administration. It was performed assessment of the quality control that was classified quality control of miss Data, outlier data and rainfall interpolation. This method will be utilized when hydrological analysis uses minute rainfall data.

• Journal of Korea Water Resources Association
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• v.37 no.3
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• pp.233-240
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• 2004

Most of hydrological analyses in the field of water resources are launched by gathering and analyzing rainfall data. Several methods have been developed to estimate areal rainfall from point rainfall data and to fill missing or ungaged data. Thiessen and Reciprocal Distance Squared(RDS) methods whose parameters are only dependent on inter-station distance are classical work in hydrology, but these techniques do not provide a continuous representation of the hydrologic process involved. In this study, kriging technique was applied to rainfall analysis in Nakdong river basin in order to complement the defects of these classical methods and to reflect spatial characteristics of regional rainfall. After spatial correlation and semi-variogram analyses were performed to perceive regional rainfall property, kriging analysis was performed to interpolate rainfall data for each grid Thus, these procedures were enable to estimate average rainfall of subbasins. In addition, poor region of rainfall observation was analyzed by spatial interpolation error for each grid and mean error for each subbasin.

• Journal of The Korean Society of Agricultural Engineers
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• v.56 no.6
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• pp.93-102
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• 2014

Generally data loading is a laborous job to develop models. Meteorological data is basic input data for hydrological models, it is provided through websites of Korea Meteorological Administration (KMA). The website of KMA provides daily meteorological observation data with tabular format classified by years, items, stations. It is cumbersome to manipulate tabular format for model inputs such as time series and multi-item or multi-station data. The provider oriented services which broadcast restricted formed information have caused inconvenient processes. Tim O'Reilly introduces "Web 2.0" which focuses on providing a service based on data. The top ranked IT companies such as google, yahoo, daum, and naver provide customer oriented services with Open API (Application Programming Interface). A RESTful web service, typical implementation for Open API, consists URI request and HTTP response which are simple and light weight protocol than SOAP (Simple Object Access Protocol). The aim of this study is to develop a web-based service that helps loading data for human use instead of machine use. In this study, the developed RESTful web service provides Open API for manipulating meteorological data. The proposed Open API can easily access from spreadsheet programs, web browsers, and various programming environments.

• Proceedings of the Korea Water Resources Association Conference
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• 2011.05a
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• pp.126-126
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• 2011

우리나라에서 본격적인 수문조사와 하천조사가 실시되기 시작한 것은 1910년대 일제 강점기라고 할 수 있다. 이 시기에는 근대적인 기술에 의해 전국적인 수문관측망이 구축되었고, 외국에서 개발된 각종 계측장비가 설치되었다. 또한 유속계가 도입되어 하천에서 유량측정이 시작된 것도 이 시기이다. 본격적인 하천개수공사도 이 시기에 시작된다. 오랫동안 자연상태로 유지되어 온 하천에 직강화 공사가 대대적으로 실시되고, 홍수피해 방지를 위한 대규모 제방 사업이 시작된 것이다. 이에 따라 일제 강점기에 하천에 관련된 많은 변화가 발생하였고, 지금까지도 그 영향이 지속 되고 있다. 일제 강점기에 이루어진 우리나라 수문조사 및 하천공사의 역사에 대해서는 거의 알려진 바가 없다. 불과 몇 권의 문헌만이 알려져 있고, 이마저도 일본어로 작성되어 있음으로 인해 자료의 분석이나 활용이 이루어지지 못했다. 또한 일제 강점기라는 특수성으로 인해서 이 시기에 이루어진 하천관련 사업은 관심의 대상이 되지 못하였다. 그러나 비록 일제 강점기에 일본인들의 주도로 이루어진 하천사업이지만 우리나라 땅에서 이루어진 우리의 역사라는 점에서 이 시기에 이루어진 하천 관련 사업에 대한 자료의 발굴, 분석 등은 매우 중요하다고 판단된다. 본 연구에서는 일제 강점기에 발간된 수문조사, 홍수피해 조사, 하천조사, 공사연보, 조사연보, 논문 등을 발굴하여 분석하였다. 이 시기에는 조사에 대한 방대한 사업이 이루어져서 조선하천조사서, 수력조사서 등의 문헌이 발간되었다. 또한 1925년, 1934년 등 이 시기에 발생한 대홍수에 대해서 다양한 형태의 조사보고서가 발간되었고, 매년 하천공사나 수문조사 결과를 담은 연보가 발간되었다. 한강, 낙동강, 대동강에 대한 홍수예보를 위한 논문도 이 시기에 작성된 바 있다. 본 연구에서 발굴한 이와 같은 문헌은 모두 100여건에 이른다. 이 시기에 작성된 문헌들은 수문조사나 하천과 관련해서 중요한 정보를 담고 있다. 1911년부터 시작된 수위 및 유량측정에 대한 상세한 방법과 결과, 연도별 수문조사 결과, 하천 직강화 이전의 하천형태, 연도별 하상변화 내역, 대홍수시의 범람상황, 하천별 개수공사 내역, 하천공사와 관련된 각종 통계 등이 사진, 그림, 도표 등의 형태로 작성되어 있어 있다. 본 연구에서는 이와 같은 자료를 분석하여 정리하였다. 본 연구에서 분석한 일제 강점기의 수문조사와 하천에 대한 내용은 향후 하천복원, 수문통계 작성, 하천공사 등에 유용하게 활용될 것으로 판단된다.

• Proceedings of the Korea Water Resources Association Conference
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• 2019.05a
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• pp.155-155
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• 2019

The Agricultural Policy/Environmental eXtender (APEX) models have been developed for assessing agricultural management efforts and their effects on soil and water at the field scale as well as more complex multi-subarea landscapes, whole farms, and watersheds. National Academy of Agricultural Sciences, Wanju, Korea, has modified a key component of APEX application, named APEX-Paddy for simulating water quality with considering appropriate paddy management practices, such as puddling and flood irrigation management. Calibration and validation are an anticipated step before any model application. Simple techniques are essential to assess whether or not a parameter should be adjusted for calibration. However, very few study has been done to evaluate the ability of APEX-Paddy to simulate the impact of multiple management scenarios on nutrients loss. In this study, the observation data from experimental fields at Iksan in South Kora was used in calibration and evaluation process during 2013-2015. The APEX auto- calibration tool (APEX-CUTE) was used for model calibration and sensitivity analysis. Four quantitative statistics, the coefficient of determination ($R^2$),Nash-Sutcliffe(NSE),percentbias(PBIAS)androotmeansquareerror(RMSE)were used in model evaluation. In this study, the hydrological process of the modified model, APEX-Paddy, is being calibrated and tested in predicting runoff discharge rate and nutrient yield. Field-scale calibration and validation processes are described with an emphasis on essential calibration parameters and direction regarding logical sequences of calibration steps. This study helps to understand the calibration and validation way is further provided for applications of APEX-Paddy at the field scales.

• Proceedings of the Korea Water Resources Association Conference
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• 2016.05a
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• pp.203-203
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• 2016

The linkage between climate change and water security, i.e., the response of water resource to the future climate change, have been of great concern to both scientific community and policy makers. In this study, the impact of future climate on water resources in Yellow River Basin in North of China has been investigated using the Coupled Land surface and Hydrology Model System (CLHMS) and IPCC AR5 projected future climate change in the basin. Firstly, the performances of 14 IPCC AR5 models in reproducing the observed precipitation and temperature in China, especially in North of China, have been evaluated, and it's suggested most climate models do show systematic bias compared with the observation, however, CNRM-CM5、HadCM5 and IPSL-CM5 model are generally the best models among those 14 models. Taking the daily projection results from the CNRM-CM5, along with the bias-correction technique, the response of water resources in Yellow river basin to the future climate change in different emission scenarios have been investigated. All the simulation results indicate a reduction in water resources. The current situation of water shortage since 1980s will keep continue, the water resources reduction varies between 28 and 23% for RCP 2.6 and 4.5 scenarios. RCP 8.5 scenario simulation shows a decrease of water resources in the early and mid 21th century, but after 2080, with the increase of rainfall, the extreme flood events tends to increase.

• Korean Journal of Agricultural Science
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• v.46 no.1
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• pp.67-78
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• 2019

The purpose of this study was to predict the water quality using the RNN (recurrent neutral network) and LSTM (long short-term memory). These are advanced forms of machine learning algorithms that are better suited for time series learning compared to artificial neural networks; however, they have not been investigated before for water quality prediction. Three water quality indexes, the BOD (biochemical oxygen demand), COD (chemical oxygen demand), and SS (suspended solids) are predicted by the RNN and LSTM. TensorFlow, an open source library developed by Google, was used to implement the machine learning algorithm. The Okcheon observation point in the Geum River basin in the Republic of Korea was selected as the target point for the prediction of the water quality. Ten years of daily observed meteorological (daily temperature and daily wind speed) and hydrological (water level and flow discharge) data were used as the inputs, and irregularly observed water quality (BOD, COD, and SS) data were used as the learning materials. The irregularly observed water quality data were converted into daily data with the linear interpolation method. The water quality after one day was predicted by the machine learning algorithm, and it was found that a water quality prediction is possible with high accuracy compared to existing physical modeling results in the prediction of the BOD, COD, and SS, which are very non-linear. The sequence length and iteration were changed to compare the performances of the algorithms.

• Journal of the Korean Association of Geographic Information Studies
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• v.21 no.4
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• pp.218-237
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• 2018

The purpose of this study is to propose a mid - range low - orbit water disaster monitoring satellite development plan to revolutionize water disaster management infrastructure through securing an independent and leading observation infrastructure and to secure safety against disaster prepared for climate change. Water and water disaster satellites should be able to detect changes in the surface of the ground and observe hydrological factors during daytime, nighttime, and bad weather. In addition, independent technology development should be possible. To do this, we selected C-band image radar payload considering domestic technology and water resources management, and suggested detailed development plan. In this way, it is reflected in the national next-generation mid-satellite 2-phase project plan to secure the basis for building a disaster monitoring system related to wide-area water.