• Korean Journal of Soil Science and Fertilizer
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• v.40 no.1
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• pp.12-17
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• 2007

This study was conducted to evaluate the characteristics of nonpoint source pollutants discharge from a small rural watershed. A typical rural area in Gongju City, Korea, was selected as the research site. Water quality and quantity in streams and rainfall samples were analyzed periodically from May to October 2005. Pollutant loads were estimated from a nonpoint source pollution model (AvSWAT, Arcview Soil and Water Assessment Tool). During the rainy season, from June 26 to 30 September 2005 and the dry season, before 26 June and after 30 September 2005, biological oxygen demands and chemical oxygen demands accounted for 91.3% and 93.7% of annual load, respectively, while total-N and total-P were 97.1% and 91.1% of annual load, respectively. The observed stream flow was $66.5m^3sec^{-1}$, while simulation stream flow was $66.2m^3sec^{-1}$. That can be assumed that simulation can be used to estimate the stream flow without practical measurement. However, the runoff trend following the occurrence of a storm event was not recorded properly.

• Journal of Korean Society of Environmental Engineers
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• v.36 no.1
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• pp.58-66
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• 2014

Water pollution problems of urban rivers due to the urbanization and industrialization have been the subject of public attention. In particular, considering the fact that the characteristics of water cycle of each basin change dramatically through the development of new towns, a large number of concerns about future water quality have been raised. However, reasonable measures to predict future water quality quantitatively have not been presented by this moment. In this study, by the linkage of annual unit load generation based on long-term monitoring results of the ministry of environment (MOE) to a semi-distributed rainfall runoff model, SWMM (Storm Water Management Model), we proposed a new methodology to estimate future water quality macroscopically and testified it to verify its applicability for the estimation of future water quality of a small watershed at G new town. As a result of the estimation using Y-EMC (Yearly based Event Mean Concentration), future water quality were simulated as BOD 18.7, T-N 16.1 and T-P 0.85 mg/L respectively which could not achieve the grade III of domestic river life guidance and these criteria could be satisfied by the reduction of domestic wastewater discharge load by over 80%. The results of this study are shown to be utilized for one of basic tools to estimate and manage water quality of urban rivers in the course of new town developments.

• Journal of Korea Water Resources Association
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• v.36 no.6
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• pp.901-910
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• 2003

The hydrologic behavior of paddy field depends largely on the irrigation and levee height management by farmers. The storage and drainage amount of paddy for storm events certainly influences the stream discharge. To understand the paddy storage effect during storm periods, a daily paddy water balance model embedding farmer's water management was developed by using 4 years (1996, 1997, 2001, 2002) field experimental data at 2 locations (Suwon and Yeoju) From the modeling, it was possible to simulate the daily ponding depth of paddy by treating paddy levee height and threshold pending depth indicating irrigation time as 10 days average parameters of the model. The storage amount(306.9 mm to 343.6 mm) showed little deviation to rainfall amount(425.1 mm to 850.8 mm).

• Journal of Korean Society on Water Environment
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• v.25 no.5
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• pp.792-802
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• 2009

The objective of this study is to construct the watershed management system with link of the non-point sources model and to estimate delivery ratio duration curves for various pollutants. For the total water pollution load management system, non-point source model should be performed with the study of the characteristic about non-point sources and loadings of non-point source and the allotment of pollutant in each area. In this study, daily flow rates and delivered pollutant loads of Nakdong river basin are simulated with modified TANK model and minimum variance unbiased estimator and SWAT model. Based on the simulation results, flow duration curves, load duration curves, and delivery ratio duration curves have been established. Then GIS analysis is performed to obtain several hydrological geomorphic characteristics such as watershed area, stream length, watershed slope and runoff curve number. As a result, the SWAT simulation results show good agreements in terms of discharge, BOD, TN, TP but for more exact simulation should be kept studying about variables and parameters which are needed for simulation. And as a result of the characteristic discharges, pollutants loading with the runoff and delivery ratios, non-point sources effects were higher than point sources effects in the small-scale test bed of Nakdong river basin.

• Journal of Korea Water Resources Association
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• v.33 no.4
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• pp.505-515
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• 2000

THe purpose of this study is to forecast of runoff hydrographs according to rainfall event in a stream. The neural network theory as a hydrologic blackbox model is used to solve hydrological problems. The Back-Propagation(BP) algorithm by the Levenberg-Marquardt(LM) techniques and Radial Basis Function(RBF) network in Neural Network(NN) models are used. Runoff hydrograph is forecasted in Bocheongstream basin which is a IHP the representative basin. The possibility of a simulation for runoff hydrographs about unlearned stations is considered. The results show that NN models are performed to effective learning for rainfall-runoff process of hydrologic system which involves a complexity and nonliner relationships. The RBF networks consist of 2 learning steps. The first step is an unsupervised learning in hidden layer and the next step is a supervised learning in output layer. Therefore, the RBF networks could provide rather time saved in the learning step than the BP algorithm. The peak discharge both BP algorithm and RBF network model in the estimation of an unlearned are a is trended to observed values.

• Proceedings of the Korea Water Resources Association Conference
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• 2007.05a
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• pp.1915-1919
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• 2007

하천관리 및 수공구조물의 설계 등을 위한 빈도별 홍수량 산정 시 이용되는 방법에는 Clark 단위도법, Snyder 단위도법, KICT 단위도법 등이 있다. 이 중 대표적인 합성단위도법인 Clark 단위도법은 실무에서 가장 많이 사용되는 방법으로 꼽을 수 있으나, Clark 단위도법 매개변수인 집중시간$(T_c)$과 저류상수(K)를 추정하는 것은 단순하지 않다. Clark 단위도법의 매개변수 추정은 계측 유역인 경우와 미계측 유역인 경우로 나눌 수 있는데 대부분의 경우 미계측 유역의 도달시간 및 저류상수를 추정하는 방법으로 홍수량을 산정하고 있는 실정이다. 본 연구에서는 감천유역을 대상유역으로 선정하였으며, 김천수위표 지점을 유출지점으로 선정하여 홍수량을 산정하였다. 호우사상은 김천수위국의 수위-유량 곡선식으로 유출량의 검정이 가능한 년도를 고려하여 1998${\sim}$2005년 사이의 호우사상 중 분석이 가능한 것으로 판단되는 부항2와 김천 강우관측소의 시강우 자료를 선정하였다. 선정된 호우사상은 1999년, 2002년, 2004년에 대한 총 6개의 시우량 자료로 WAMIS(국가수자원종합정보시스템)와 한강홍수통제소(www.hrfco.go.kr)의 자료실에서 제공하는 한국수문조사연보 자료를 이용하였다. 선정된 호우사상과 WMS모형을 이용하여 산정된 유역면적 및 강우관측소 별 Thiessen 가중계수를 이용하여 HEC-1모형의 최적화기법으로 Clark 단위도법의 집중시간$(T_c)$과 저류상수(K)를 산정하였으며, 계측유역의 매개변수를 산정하는 방법 중 저류방정식을 이용하는 방법을 이용하여 저류상수를 산정하여 비교하였다. 집중시간의 경우 1999년과 2002년에 비해 2004년의 결과값이 작게 산정되었으며, 저류상수의 경우 2004년의 결과값이 크게 산정되었다. 그러나, 저류방정식을 이용하여 저류상수를 결정하는 방법으로 산정한 저류상수는 비교적 일관성 있게 산정되었다.

• Journal of Wetlands Research
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• v.16 no.2
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• pp.221-233
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• 2014

Soil erosion, transportation, and sedimentation by water flow often occur in a stream. This excessive occurrence threatens the safety of hydraulic structures, and aggravates natural disasters like flood. To prevent soil disaster according to the soil erosion, it is necessary to predict accurate sediment outflow primarily. Besides, it is very important to choose appropriate models by basin characteristics, to estimate accurate quantity of related factors, and to acquire available hydrological data. Therefore, the purpose of this study is to estimate soil erosion amount and sediment amount according to rainfall-runoff by using rainfall, discharge, and sediment in the Seolmacheon experimental catchment. And, it proposed sediment delivery ratio of the Seolmacheon catchment by result of studying sediment delivery ratio. Hereafter, this study will estimate sediment delivery ratio by basin characteristics, and formulate the method of estimating soil erosion and sediment outflow in various conditions by applying the results in other catchments.

• Proceedings of the Korea Water Resources Association Conference
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• 2019.05a
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• pp.273-273
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• 2019

우리나라 하천에는 33,893개의 보(국가어도정보시스템)가 설치되어 있는 것으로 조사된다. 다양한 형태 및 가동여부 등으로 인해 동일한 산정 방법을 적용할 수는 없으나, 각각의 특성을 파악하여 유량 산정이 가능하게 한다면 홍수 시 유량측정이 이루어지지 못한 하천의 유량을 추정 하는데 활용 할 수 있을 것이다. 횡단구조물을 이용한 유량산정 방법은 다양한 실험식이 존재하여 보의 형태 및 수집 가능한 정보를 고려한 적절한 선택이 필요하다. 본 연구에서는 북한강 지류인 화천천에 위치한 배머리보(폭 122m)를 이용하여 유량산정을 실시하였다. 배머리보 상류에는 2018년 유량측정이 이루어진 용신교 수위관측소(한국수력원자력(주))가 위치하여 연속적인 수두 측정이 가능하였으며, 자유 흐름 조건이 유지된 2018년 8월 29일~31일 홍수사상에 대해 보를 이용한 유량산정 적성성을 검토하였다. 배머리보 형태를 고려해 광정위어공식과 한국산업규격에서 제공한 유량계수를 적용($Q=2.026bh^{3/2}$)하였다. 배머리보를 이용하여 유량을 산정한 결과 유량 $200m^3/s$ 이상에서 수위-유량관계곡선식에 의한 유량과 광정웨어 공식을 이용하여 산정한 유량이 잘 일치하는 것으로 검토되었다. 유량 $200m^3/s$이상에서 유량편차가 $-13.96{\sim}14.02m^3/s$(절대편차 평균 $9.02m^3/s$)를 보였으며, 편차율은 -2.98~6.04%(절대편차율 평균 2.09%)를 보였다. 이러한 결과로 볼 때 실제 하천에서 보를 이용한 유량산정이 가능할 것으로 판단된다.

• Journal of Korea Water Resources Association
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• v.52 no.2
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• pp.97-105
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• 2019

In this study, the baseflow indices in Nakdong river watershed and the whole country's river were calculated by using SWAT model and PART method. The annual averaged baseflow in the Nakdong river watershed was estimated at 40% - 44% of the total discharge rate, and it is found to be higher than 90% during the winter months of December and January. An analysis of the baseflow index from 317 gauge stations across the country revealed that the contribution of baseflow to the nation's stream flow rate stood at an annual average of 40%, ranging from less than 20% to over 80% by region. Also, the impact of the decreasing baseflow due to land use changes in 1975 and 2000 was analyzed in Keumhogang river watershed under the same weather conditions. The results revealed that the number of days under the standard instream flow increased by 19-24 days as a result of the increase in the urbanization rate.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.4 no.1
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• pp.103-112
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• 1984

This study is an effort to develop a series of empirical procedure for the determination of design flood for a small watershed based on the unit hydrograph theory. It is shown that a flood discharge of a watershed with a specific return period can be expressed as a product of its watershed area, rainfall factor, runoff factor and flood peak reduction factor. Since the procedures for the determination of rainfall factor and runoff factor were already developed in the previous study (13) a series of step-by-step procedure is devised to empirically determine the flood peak reduction factor in the present study. Using the methodology developed herein the 50-year design flood, which is of concern in the drainage of agricultural lands, is estimated for a watershed on upper Kyungan River and compared with the design floods by the existing methods now in use. The flood peak reduction factor was correlated with the dimensionless parameter consisted of the rainfall duration divided by the basin lag time, which was computed from the derived unit hydrographs by the method of moment. The unit hydrographs of various durations were synthesized by the method of build up and S-curve. A multiple correlation was also made between the basin lag time and the physiographic parameters of the watershed, i.e., the stream length and the average stream slope.