• Proceedings of the Korea Water Resources Association Conference
• /
• 2006.05a
• /
• pp.1822-1829
• /
• 2006

본 연구에서는 계산된 유량과 실측 유량을 비교하여 Clark 단위도 방법의 매개변수를 추정하고자 하였다. 오산천과 진위천 상류유역에 대하여 Arcview와 WMS로 지형자료에 대한 전 처리를 한후, HEC-HMS 프로그램을 이용하여 유출량을 산정하였다. 2001년부터 2005년까지 4개의 사상에 대하여 강우량, 기흥저수지와 이동저수지의 실제 방류량을 이용하여 유출량을 산정하였으며, Clark 모형의 매개변수를 Russel 공식, Sabol 공식 및 HEC-HMS 프로그램에 내장된 Nelder-Mead 최적화 방법을 이용하여 매개변수를 각각 산정하여 회화 지점의 실측 유출량과 비교.평가하였다. 빈도가 큰 유출사상의 경우에는 Sabol 식을 적용한 결과가 Russel 식을 적용한 모의결과보다 첨두유량의 재현성이 우수하게 나타났으며, 유출량이 작은 경우에는 Russel 식을 적용한 모의결과가 우수하였다. 첨두가 중제곱평균제곱근오차, 잔차자승의 합, 절대잔차의 합 등 3가지의 서로다른 목적함수를 적용하여 매개변수를 자동 보정하였을 때, 목적함수에 따른 첨두유량의 오차는 거의 동일하였으며, 첨두시간에 대한 오차는 첨두가중제곱평균제곱근오차를 적용했을 때 가장 작은 것으로 분석되었다. 그리고 Clark 유역 추적모형의 자동보정을 통하여 추정한 매개변수인 도달시간과 저류상수는 강우사상에 따라서 변동하는 특성을 나타내기 때문에 최적의 도달시간 및 저류상수는 홍수사상별로 추정되어야 하며 이 결과는 홍수량 산정을 위한 매개변수 추정과정의 비유일성 및 복잡성을 암시하고 있다.

• Journal of the Korean Institute of Gas
• /
• v.22 no.2
• /
• pp.34-45
• /
• 2018

The cleat system in coalbed methane (CBM) reservoirs is generally occupied by water which liberated during the coalification process, and behavior of water have influence on CBM production performance. Therefore, it is essential to investigate the effect of the water saturation to operate the degasification process and predict the CBM production performance properly. In this study, type curve analyses were performed on CBM reservoirs under various water saturation to improve the prediction of production performance. A CBM reservoir models with fully-, modestly-, and undersaturated reservoir were built to get production data using GEM by CMG Ltd., and the data were matched with Fetkovich, Palacio-Blasingame(P-B), and Agarwal-Gardner (A-G) type curve. The results showed that undersaturated reservoir was successfully matched by A-G type curve, while the Fetkovich type curve was inappropriate for matching in the late time. The modestly saturated model could be almost corresponded with all the type curve methods at late production period. For the fully saturated model, after peak production had been reached, both P-B and A-G methods showed a proper match to the reservoir production data without long-term production period. Based on the results, merit and demerit of each type curve under specific water saturation were analyzed and listed. Therefore, it is believed that the production data analysis with proper type curve model considering water saturation can be performed to predict accurate production performance.

• Journal of Korea Water Resources Association
• /
• v.36 no.3 s.134
• /
• pp.385-398
• /
• 2003

The concept of the effective storage ratio has been suggested to determine the size of detention pond by the previous researchers. The 11 pump - pond facilities in Dongdu-chun city were selected to analyze the critical duration for design rainfall and the storage ratio for each rainfall duration in this study It has been then found that the criteria of the maximum storage ratio is not reasonable for determining the size of detention pond because the difference of storage ratio with respect to each rainfall duration is too small. Moreover, since the size of pond compared with the pump capacity is not always big enough, the pump should be frequently operated, which may result in pump failure. Thus, the pond should be sufficiently sized to prevent the possibility of the pump failure due to frequent operation. According to the analyses for changing pump capacity, it has been found that if the function of the pond compared with the pump is concentrated, determining the size of pond based on the storage ratio is operationally feasible for even small basin. Thus, an improved procedure based on the storage ratio for determining the size of detention pond in small basin has been suggested. The results by the proposed procedure considering pump switching frequency may lead to reasonable pump operation. A simple linear programming model has been also adopted to figure out the relationship between pump capacity and pond size. It has been shown that the determination lot the size of detention pond based on conventional hydrologic flood routing in pond is feasible for only urban districts not rural areas.

• Journal of Korea Water Resources Association
• /
• v.50 no.12
• /
• pp.827-836
• /
• 2017

The most important parameters of the Muskingum method, widely used in hydrologic river routing, are the storage coefficient and the weighting factor. The Muskingum method does not consider the lateral inflow from the upstream to the downstream, but the lateral inflow actually occurs due to the rainfall on the watershed. As a result, it is very difficult to estimate the storage coefficient and the weighting factor by using the actual data of upstream and downstream. In this study, the flow without the lateral inflow was calculated from the river flow through the hydraulic flood routing by using the HEC-RAS one-dimensional unsteady flow model, and the method of the storage coefficient and the weighting factor calculation is presented. Considering that the storage coefficient relates to the travel time, the empirical travel time formulas used in the establishment of the domestic river basin plan were applied as the storage coefficient, and the simulation results were compared and analyzed. Finally, we have developed a formula for calculating the travel time considering the flow rate, and proposed a method to perform flood routing by updating the travel time according to the inflow change. The rise and fall process of the flow rate, the peak flow rate, and the peak time are well simulated when the travel time in consideration of the flow rate is applied as the storage coefficient.

• Journal of Korea Water Resources Association
• /
• v.53 no.9
• /
• pp.681-690
• /
• 2020

Generally, the design capacity of the rainwater harvesting unit is determined by trial and error method that is repeatedly calculating various analysis scenarios with capacity, reliability, and rainwater utilization ratio, etc. This method not only takes a lot of time to analyze but also involves a lot of calculations, so analysis errors may occur. In order to solve the problem, this study suggested a way to directly determine the minimum capacity to meet arbitrary target reliabilities using the global optimization method. The method was implemented by simulation model with particle swarm optimization (PSO) algorithms using Python language. The pyswarm that is provided as an open-source of python was used as optimization method, that can explore global optimum, and consider constraints. In this study, the developed program was applied to the design data for the rainwater harvesting constructed in Cheongna district 1 in Incheon to verify the efficiency, stability, and accuracy of the analysis. The method of determining the capacity of the rainwater harvesting presented in this study is considered to be of practical value because it can improve the current level of analytical technology.

• Tunnel and Underground Space
• /
• v.23 no.3
• /
• pp.169-179
• /
• 2013

Well testing in unconventional reservoirs, such as tight or shale gas formations, presents considerable challenges. It is difficult to estimate the reservoir properties in ultra-low permeability formation because of poor inflow prior to stimulation and excessive test duration. Moreover, radial flow may not develop in hydraulically fractured horizontal wells. For these reasons, the cost of test is high and the accuracy is relatively low. Accordingly, industry is turning to an alternate testing method, diagnostic fracture injection test (DFIT), which is conducted prior to the main hydraulic fracture treatments. Nowadays, DFIT are regarded as the most practical way to obtain good estimates of reservoir properties in unconventional reservoirs. Various methods may be used for interpreting DFIT data. This paper gives an explanation of those methods in detail and examines three actual field data. These show how various analysis methods can be applied to consistently interpret fracture closure pressure and time, as well as before and after closure flow regimes and reservoir properties from field data.

• Journal of Korea Water Resources Association
• /
• v.46 no.6
• /
• pp.597-611
• /
• 2013

This paper presents the methodology for construction of time-area curve via the width function and thereby rational estimation of time of concentration and storage coefficient of Clark model within the framework of method of moments. To this end time-area curve is built by rescaling the grid-based width function under the assumption of pure translation and then the analytical expressions for two parameters of Clark model are proposed in terms of method of moments. The methodology in this study based on the analytical expressions mentioned before is compared with both (1) the traditional optimization method of Clark model provided by HEC-1 in which the symmetric time-area curve is used and the difference between observed and simulated hydrographs is minimized (2) and the same optimization method but replacing time-area curve with rescaled width function in respect of peak discharge and time to peak of simulated direct runoff hydrographs and their efficiency coefficient relative to the observed ones. The following points are worth of emphasizing: (1) The optimization method by HEC-1 with rescaled width function among others results in the parameters well reflecting the observed runoff hydrograph with respect to peak discharge coordinates and coefficient of efficiency; (2) For the better application of Clark model it is recommended to use the time-area curve capable of accounting for irregular drainage structure of a river basin such as rescaled width function instead of symmetric time-area curve by HEC-1; (3) Moment-based methodology with rescaled width function developed in this study also gives rise to satisfactory simulation results in terms of peak discharge coordinates and coefficient of efficiency. Especially the mean velocities estimated from this method, characterizing the translation effect of time-area curve, are well consistent with the field surveying results for the points of interest in this study; (4) It is confirmed that the moment-based methodology could be an effective tool for quantitative assessment of translation and storage effects of natural river basin; (5) The runoff hydrographs simulated by the moment-based methodology tend to be more right skewed relative to the observed ones and have lower peaks. It is inferred that this is due to consideration of only one mean velocity in the parameter estimation. Further research is required to combine the hydrodynamic heterogeneity between hillslope and channel network into the construction of time-area curve.

• Journal of the Korean Institute of Gas
• /
• v.2 no.4
• /
• pp.73-78
• /
• 1998

This paper considers the applicability of a pseudosteady-state approach to the long-time behavior of real gas flow in a closed reservoir. The method involves a combination of a linearized gas diffusivity equation using a normalized pseudotime and a material balance equation. For the simulation of field-scale problems with multiple wells of differing production rates over extended production periods, the pseudosteady-state equation was solved successively for each flow period. Results from this study show that the approach provides a fast and accurate method for modeling the long-time behavior of gas reservoirs under depletion conditions.

• Magazine of the Korean Society of Agricultural Engineers
• /
• v.38 no.2
• /
• pp.75-86
• /
• 1996

The formulas for estimating the constants of storage function model including K and TL for runoff analysis and a distributed storage function model are discussed in this study. First, the relations between parameters of the storage function model and the kinematic runoff model are theoretically examined, and then optimum constants of storage function model are obtained by the Standardized Davidson-Fletcher-Powell (SDFP) method. Through this analysis, theoretical formulas were obtained as $K = 0.63 {\alpha} KsB{^0.6}$ and $T_{L}=0.11 {\alpha} KsB{^0.6} r{^0.4} {_e}$, which are difficult to use practically because of the unclarified definition of shape factors. From a practical point of view, empirical formula were derived as $K=15.6{^0.3} {_m}$ and $T_{L}=2.1B{^0.36} {_m} {_e}/r{^0.4} {_e}$ for applied watersheds. The proposed formulas are verified for several recoded floods at a few points of watersheds. It is also found that the distributed storage function. can be applied to flood runoff analysis using the new formulas aboved mentioned.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2016.05a
• /
• pp.5-5
• /
• 2016

기후변화에 따른 수환경의 변화로 도시홍수로 인한 인명 및 재산피해가 증가하여 도시홍수에 대한 중요성이 급격히 부각되는 상황이지만 국내에서는 도시 내배수 시스템의 선진화기술 구축 및 그와 관련된 연구는 미흡한 실정일 뿐만 아니라 효과적인 침수 저감도 어려운 실정이다. 도시지역에서의 내수침수를 효과적으로 방어할 수 있는 구조적, 비구조적 홍수방어 대책의 수립이 시급한 실정이다. 현재 기존의 도시침수 저감 대책들은 유하시설의 용량 증설 및 통수능 확보를 초점으로 하는 구조적인 대책에 머물러 있으며, 유하시설 위주의 대책은 하류에서의 더 큰 홍수를 발생시킬 위험이 있다. 기존 내배수시설의 전체적인 확장은 막대한 예산과 시간을 필요로 할 뿐만 아니라 지구온난화로 인한 이상기후 및 국지성 집중호우에 완벽하게 대응하기 곤란하므로 구조적인 대책과 더불어 집중호우에 대비할 수 있도록 각 시설물의 기능 및 경제성을 최대로 하며 방재성능을 향상시킬 수 있는 비구조적인 대책이 동시에 수립되어야 한다. 본 연구에서는 비구조적인 대책 중 하나로 빗물펌프장 및 빗물저류조의 연계운영에 초점을 맞추었다. 모니터링 지점을 선정하여 빗물저류조의 추가저류공간을 확보하는 운영을 실시하고 빗물 펌프장 유수지의 수위를 낮추어 내수침수를 저감시킬 수 있는 방법을 제안하였다. 기존의 운영과 본 연구에서 제안한 연계운영을 비교하고 효과를 분석하였다.