• Journal of Korea Water Resources Association
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• v.35 no.1
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• pp.51-64
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• 2002

In this study, the formulation of the developed mixed-integer programming model for a multi-reservoir system including hydro-electric power generation (park et al., 2001) has been improved for multiple reservoir system operation using risk evaluation criteria. Sequential linear programming(SLP) was applied for the linearization of the hydro-electric energy term in the model. In order to allocate monthly reservoir release reasonably the value of weight for hydro-electric energy was assigned by level of power generation hour. The improved model was applied to the five reservoirs system in the Han river. And could be confirmed the availibility of new formulation appling risk evaluation criteria.

• Proceedings of the Korea Water Resources Association Conference
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• 2007.05a
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• pp.2059-2063
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• 2007

장기 수자원계획시 댐군의 연계운영을 위한 물수지분석 모형으로 HEC-5 모형과 K-ModSim 모형을 선정하고, 이에 대한 댐군의 연계운영 효과를 비교 평가를 수행하였다. K-ModSim 모형은 범용 우선순위 목적 선형최적화 모형으로, 조절점 및 저수지조작에 대한 우선순위를 지정할 수 있는 반면, HEC-5 모형은 목적별 저수지 조작의 우선순위가 지정되며, 등가저수지 개념을 사용하여 방류 우선순위를 결정하도록 되어있다. 이와 같은 연계운영 방식의 차이는 적정한 시기에 조절점에서의 물부족이 발생하는지 여부를 결정짓는 매우 중요한 요소이다. 따라서 본 연구에서는 가뭄발생 상황에 대한 각 모형의 연계운영효과를 비교 분석함으로써 급속히 변화하고 있는 수자원 이용환경에서 보다 합리적인 댐군의 연계운영 방안을 제시하고자 한다.

• Proceedings of the Korea Water Resources Association Conference
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• 2007.05a
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• pp.2089-2093
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• 2007

저수지군 연계운영 문제는 서로 상충되는 목적들이 존재하고, 다양한 평가 기준들이 존재하는 다목적 특성을 갖는 문제이다. 때문에 저수지군 연계운영 문제에 다중목적계획법이 많이 사용되고 있으나 문제의 해결을 위해 사용한 다수의 목적간의 가중치 설정에 의사결정자의 주관적요소가 반영 될 수도 있고, 설정된 가중치에 따라 결과 값이 민감하게 반응하여 의사결정자가 바람직한 가중치 설정에 어려움이 있다. 본 연구의 목적은 다중 목적 특성이 존재하는 저수지군 연계운영 문제에 다요소 의사결정기법 적용하여 바람직한 저수지별 저수 가중치를 선정하는 방법을 제안하는 것이다. 제안하는 저수 가중치 선정 절차는, 우선 GA-CoMOM (Genetic-Algorithm Coordinate Multi-reservoir Operation Model)을 통해 수계 전체 관점에서 저수량과 발전량의 상충되는 목적에 대한 파레토 최적해와 각 최적해에 해당하는 저수지별 저수 가중치를 도출한다. 다음 단계로 다요소 의사결정기법중에 하나인 수정된 거리척도 기반의 DEA 순위 선정 절차를 이용하여 도출된 최적해들의 운영 결과를 평가하여 파레토 최적해군 중에 선호해를 결정하고, 결정된 선호해의 저수지별 저수 가중치를 해당 기간의 저수 가중치로 선정한다. 설명한 선호 가중치 선정 절차를 금강 수계에 적용해 보고 저수지 연계운영에서 바람직한 가중치를 도출할 수 있음을 보인다.

• Proceedings of the Korea Water Resources Association Conference
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• 2020.06a
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• pp.171-171
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• 2020

Decision making strategies should consider both adaptiveness and robustness in order to deal with two main characteristics of climate change: non-stationarity and deep uncertainty. Especially, robust strategies are different from traditional optimal strategies in the sense that they are satisfactory over a wider range of uncertainty and may act as a key when confronting climate change. In this study, a new framework named Robust Stochastic Dynamic Programming (R-SDP) is proposed, which couples previously developed robust optimization (RO) into the objective function and constraint of SDP. Two main approaches of RO, feasibility robustness and solution robustness, are considered in the optimization algorithm and consequently, three models to be tested are developed: conventional-SDP (CSDP), R-SDP-Feasibility (RSDP-F), and R-SDP-Solution (RSDP-S). The developed models were used to derive optimal monthly release rules in a single reservoir, and multiple simulations of the derived monthly policy under inflow scenarios with varying mean and standard deviations are undergone. Simulation results were then evaluated with a wide range of evaluation metrics from reliability, resiliency, vulnerability to additional robustness measures. Evaluation results were finally visualized with advanced visualization tools that are used in multi-objective robust decision making (MORDM) framework. As a result, RSDP-F and RSDP-S models yielded more risk averse, or conservative, results than the CSDP model, and a trade-off relationship between traditional and robustness metrics was discovered.

• Journal of Korea Water Resources Association
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• v.55 no.6
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• pp.437-446
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• 2022

In April 2020, the Korean government decided to operate the Hwacheon reservoir, a hydropower reservoir to supply water, and it is currently under pilot operation. Through the pilot operation, the Hwacheon reservoir is the first among the hydropower reservoirs in Korea to make a constant release for downstream water supply. In this study, the water supply capacity of the Hwacheon reservoir was estimated using the inflow data of the Hwacheon reservoir. A simulation model was developed to calculate the water supply that satisfies both the monthly water supply reliability of 95% and the annual water supply reliability of 95%. An optimization model was also developed to evaluate the water supply capacity of the Hwacheon reservoir. The inflow data used as input data for the model was modified in two ways in consideration of the impact of the Imnam reservoir. Calculating the water supply for the Hwacheon reservoir using the two modified inflows is as follows. The water supply that satisfies 95% of the monthly water supply reliability is 26.9 m³/sec and 24.1 m³/sec. And the water supply that satisfies 95% of the annual water supply reliability is 23.9 m³/sec and 22.2 m³/sec. Hwacheon reservoir has a maximum annual water supply of 777 MCM (Million Cubic Meter) without failure in the water supply. The Hwacheon reservoir can supply 704 MCM of water per year, considering the past monthly power generation and discharge patterns. If the Hwacheon reservoir performs a routine operation utilizing its water supply capacity, it can contribute to stabilizing the water supply during dry seasons in the Han River Basin.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.13 no.2
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• pp.141-149
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• 1993

Production of hydro-energy is random in its output amount due to the characteristics of the reservoir inflows. Therefore, it is necessary to provide the rationality in determining the amount of energy for a supply contract. This study presents a methodology for determining reasonably reliable amount of the energy supply considering the energy sale-incomes associated with the penalties which are subject to inflow-reliabilities. The objective function consists of the returns of energy sales and the risk-loss function to reflect statistically relevant risks. A range of the coefficient of the risk-loss function was figured out by its sensitivity analysis. The risk-loss herein means the penalty which should be paid by the energy supplier in case that the level of the energy supply is behind the contracted amount. And the reliability of reservoir inflow is defined by the exceedance probability of the inflow. The log-normal distribution was accepted as the probability density function of monthly inflows on the level of significance at 5%. Golden-ratio searching was applied to identify the optimal reliability and Incremental Dynamic Programming was used to maximize generation of the hydro-power energy in reservoir operation. The algorithm was the applied to the Daechung multi-purpose reservoir and hydro-power plant system in order to verify its usefulness.

• Journal of Korea Water Resources Association
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• v.51 no.7
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• pp.555-564
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• 2018

The detention reservoir is a hydraulic structure that constructs a levee on the inland of river and sets up side weir in a section of the levee, and this facility stores a part of the flood volume in case of a flood event over a certain scale. In order to optimize the operation of detention reservoir, it is necessary to review the linkage with existing facilities in the river. In this study, the effect of water level reduction and the flow distribution was analyzed according to the location of the side weir in the detention reservoir considering the run-of-the-river gate. Two radial gates were installed in the experimental channel, and the water level in channel and the overflow of weir were measured by moving the location of the side weir upstream from the gate. As a results of experiment, it was confirmed that the water level reduction is more remarkable as the location of the side weir was closer to the gate, and the effect of flow distribution is not greatly changed. When two or more side weirs were operated, it is confirmed that the sufficient storage space was secured and the water level reduction effect with the location of the side weir is not large. In addition, the water level reduction rate according to the location of the side weir was estimated by empirical formula and it is provided as basic data that can be used in the planning of the detention reservoir.

• Magazine of the Korean Society of Agricultural Engineers
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• v.24 no.1
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• pp.44-52
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• 1982

Recently, estuary reserovoirs have been actively constructed in Korea and also in Japan there are a large number of estuary reservoirs constructed. But most of the estuary reservoirs are located at the downstream of a river where geographical condition is best for the construction of an enclosing dam. And an effective utilization of water from the estuary reservoir seems to be difficult even if estuary reservoirs are considered to be the water resources the most available for their watershed. Studies on estuary reservoirs so far have been mainly concentrated on the physical and engineering problems of the dam construction itself. The purpose of the present study is to review the estuary reservoir planning in connection with the water resources development and to study a basis of the planning. First, the levels of water use in Korea and Japan were compared with those of other countries in the world. And then, some representative reservoirs were selected to study the roles of a reservoir and water-using conditions in the watershed. Based on the study, a survey was given on the relation between a dam construction upstream and an estuary reservoir construction downstream of a river. Finally, a comprehensive examination was made of the bases of estuary reservoir planning. (1) The estuary reservoir planning is deeply related to the plan for water use develo- pment in the watershed. After the upstream water resources were fully developed up to the most, water reso- urces development by an estuary reservoir should be started. (2) If an estuary lake has a capacity big enough, it can store flood discharge of the watershed without any loss and become a basic facility that will bring about the maxi- mum use of water from the watershed. (3) Estuary reservoirs store water used in the upstream watershed, so recycling of water use is attained by the reservoir. Water in the estuary lake is difficult to be fresh water in its long run. Therefore, estuary reservoir should be located at a place where polluted water is purified and refused. All the planning should be based on the assumption that water in the estuary lake is not fresh but polluted after a long time. (4) The estuary lake can only supply water to the lower basin directly. But the upstream area is benefited from the estuary lake by exchange of irrigation water sources between the lower and the upper area. So a large-scale exchange plan between new and existing water resources is important. By constructing estuary reservoirs and the exchange of water sources between upper and lower areas, the reasonable maximum use of water from the whole watershed is at- tained. (5) The big problem coming from the water resources development by an enclosing estuary is salt water intrusion into the lake. To maintain the estuary lake salt-free, multi-purpose use of the lake should be avoided. It is necessary to take such fundamental measures as abolition of back flow operation of gate, and the closing of the fish port and the fish ladder. The results mentioned above were found in this study and these results of this study could be used for the adequate planning of estuary reservoirs in connection with the maximum water use of the watershed.

• Journal of Korea Water Resources Association
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• v.55 no.7
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• pp.505-513
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• 2022

Recently, uncertainty in predicting available water resources is gradually increasing due to climate change and extreme weather conditions. Social interest in water management such as flood and drought prevention is also increasing, and after the unification of water management implemented in 2018, domestic water management is facing a major turning point. As part of such strengthening of water management capabilities, various studies are being conducted to utilize a hydropower dam for flood control and water supply purposes, which was mainly operated for hydroelectric power generation. However, since the dam evaluation methods developed based on a multi-purpose dam are being applied to hydropower dams, an additional evaluation approach that can consider the characteristics of hydropower dams is required. In this study, a new water supply capacity evaluation method is presented in consideration of the operational characteristics of hydropower dams in terms of water supply, and a connected reservoir simulation method is proposed to evaluate the comprehensive water supply capacity of a dam group operating in a river basin. The presented method was applied to the hydropower dams located in the Bukhan River basin, and the results of the water supply yield of individual dams and multi-reservoir systems were compared and analyzed. In the future, the role of hydropower dams for water supply during drought is expected to become more important, and this study can be used for sustainable domestic water management research using hydropower dams.

• Water for future
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• v.17 no.1
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• pp.37-43
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• 1984

Linear tracking problem I analytically solved with the buadratic performance measure. This theory has the inherent drawbacks in application, because the tracking assumes no boundness of the control and state vectors. The tracking was performed to the discrete system and interrupted subject to the violation. Multi-level tracking was intended based on the concept of the Bellman's Principle of Optimality in this paper. The tracking is iterated to get the desired trajectory which is not known in advance. An application was made to real operation of 6 rervoirs over 36 monthly periods for the Han river.