• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 1998.10a
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• pp.279-286
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• 1998

The south-western part of Korea is situated in an unbalance of water supply and demand relating to the Keum, Mankyung, Dongjin and Youngsan River and their estuary reservoirs. For example, the Keum River estuary reservoir is discharging the larger amount of yearly runoff into the sea due to the small storage capacity, while Saemankeum estuary reservoir which is under construction, has the smaller runoff amount comparing with its storage capacity, And the downstream area of the Youngsan River, such as Youngkwang, Youngam are deficient in water due in larger demand and smaller supply. In order to solve the above unbalanced water supply and demand and also to improve the water use efficiency, the Hierarchical Operation Model for Multi-reservoir System(HOMMS) has been developed and applied to analyze the multi-reservoir operation assuming that the above reservoirs were linked each other. The result of this study shows that 2,148MCM of annual additional water requirement for agricultural and rural water demands are required in this region at 2011 of target year, and these demands can be resolved by diverting and reusing 1,913MCM of the released water from the estuary reservoirs into the sea.

• Magazine of the Korean Society of Agricultural Engineers
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• v.42
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• pp.17-23
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• 2000

A decision support system for determining reservoir capacity, named as KORESIDSS (KOwaco's REservoir SIzing Decision Support System), was developed. The system is composed of three subsystems; a database/information subsystem, a model subsystem, and an output subsystem. This system is operated using MS-Windows with a GUI (Graphic User Interface) system developed using Visual Basic 5.0. As a continuous runoff model, the DAWAST model (DAily WAtershed STreamflow model) developed by Noh(1991) was and its analysis module was developed. This system was applied to a newly-planned dam, the Cheongyan Dam, Which will be located in Cheongyang-Gun, Chungcheongnam-Do and it was proved to be applicable in determining reservoir storage.

• Journal of The Korean Society of Agricultural Engineers
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• v.57 no.4
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• pp.73-84
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• 2015

An embankment raising project on 113 agricultural reservoirs in Korea was implemented in 2009 to increase water supply capacity for agricultural water and instream uses. This study evaluated the future water supply capacity of the Imgo reservoir at which the agricultural reservoir embankment raising project was completed, considering climate change scenarios. The height of the embankment of the reservoir was increased by 4.5 m, thereby increasing its total storage from 1,657.0 thousand to 3,179.5 thousand cubic meters. To simulate the reservoir water storage with respect to climate changes, two climate change scenarios, namely, RCP 4.5 and RCP 8.5 (in which greenhouse gas reduction policy was executed and not executed, respectively) were applied with bias correction for reflecting the climate characteristics of the target basin. The analysis result of the agricultural water supply capacity in the future, after the agricultural reservoir embankment raising project is implemented, revealed that the water supply reliability and the agricultural water supply increased, regardless of the climate change scenarios. By simulating the reservoir water storage considering the instream flow post completion of the embankment raising project, it was found that water shortage in the reservoir in the future is not likely to occur when it is supplied with an appropriate instream flow. The range of instream flow tends to decrease over time under RCP 8.5, in which the greenhouse gas reduction policy was not executed, and the restoration of reservoir storage was lower in this scenario than in RCP 4.5, in which greenhouse gas reduction policy was executed.

• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.515-515
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• 2022

Climate change is strongly threatening the performance of agricultural reservoirs, which are instrumental in ensuring uninterrupted water supplies for rice cultivation in Korea. In this study, various performance indices were derived and overall sustainability of the 400 agricultural reservoirs was evaluated in the context of climate change trends during 1973-2017. Rice crop evapotranspiration, irrigation water requirements, runoff generation in the upstream watershed, and volumetric evaporation losses were plugged into a water balance model to simulate the reservoir operation during the study period. Resilience, reliability, and vulnerability are the three main indicators of reservoir performance, and these were combined into a single sustainability metric to define the overall system credibility. Historical climate data analysis confirmed that the country is facing a gradual warming shift, particularly in the central and southern agricultural regions. Although annual cumulative rainfall increased over the last 45 years, uneven monthly rainfall distribution during the dry and wet seasons also exacerbated the severity and frequency of droughts/floods. For approximately 85% of the selected reservoirs, the sustainability ranged between 0.35 to 0.77, and this range narrowed sharply with time, particularly for the reservoirs located in the western and southern coast regions. The study outcomes could help in developing the acceptable ranges of the performance indices and implementing appropriate policy and technical interventions for improving the sustainability of reservoirs with unacceptable ranges of the performance indices.

• Journal of Korean Society of Water and Wastewater
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• v.21 no.2
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• pp.215-224
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• 2007

The purpose of this study was to estimates water supply reliability indices of the water supply by Allocation Rules(AR) for parallel reservoirs. Rule (A) can be considered it as only current storage, Rule(B) can be considered it as current storage and inflow and Rule(C) can be considered it as current storage, inflow and water supply capacity. First, conditions of water supply are divided by Condition I for the monthly constant water supply and Condition II for the monthly varied water supply. Second, results of allocation coefficients are revealed the smallest different at Rule(C). The analysis of water supply showed that the capability of water supply is superior to the Rule(B), it is superior to the Rule(C) on the base of the balance of water supply. The reliability analysis was highly showed at the Rule(B) and Rule(C). A methodology for the analysis of water supply was developed and applied to the parallel reservoir system from this research, The operation rule for the parallel reservoir can be slightly modified and successfully applied to the different kinds of the parallel reservoir system.

• Journal of Environmental Science International
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• v.25 no.8
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• pp.1057-1063
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• 2016

The heat budget is investigated in the Gumi Reservoir of the Nakdong river. In warm climate season, solar radiation effects play a important role in the change of water temperature. The features of the surface heat balance are almost derived by the latent heat flux and the solar radiation flux. On the other hand, in cold climate season, change of heat stored in the water is mainly dominated by latent and sensible heat transfer between water and air, since flux of solar radiation and loss of outgoing long wave radiation balance approximately. For the annual averages, net flux of radiation, evaporation(latent heat) loss are dominant in the Gumi reservoir. The evaporation losses are dominant from spring to early winter. This means that the Gumi reservoir rolls like a lake of thermal medium or deep depth.

• Journal of The Korean Society of Agricultural Engineers
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• v.53 no.6
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• pp.101-109
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• 2011

The purpose of this study was to establish the methodology for providing the environmental flows from irrigation reservoir. Reservoir water budget for study area was analyzed to simulate the water supply scenarios for environmental flows. Bonghyun and Hi reservoirs area, located in Gyeongnam, Gosung-gun, Hi-myeon, were selected for study watersheds and streams for this study. Reservoir operation was simulated to determine the envionmental flows supply amount from March to October with the constraint that environmental flow supply was restrained when the storage of reservoir were below the half or one-third of effective storage. The simulated results indicated that the supply of environmental flows with the amount of 200 ton/day and 600 ton/day resulted in up to 15 mm and 29 mm of runoff depth increase in the downstream, respectively. The effect of environmental flows supply from existing irrigation reservoir was not significant because the irrigation reservoir was not designed to supply the environmental flows. It is necessary to remodel the irrigation reservoir and develop the reservoir operation technique, to meet the need for the environmental flows.

• Magazine of the Korean Society of Agricultural Engineers
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• v.34 no.1
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• pp.33-40
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• 1992

Up to now, monthly water balance analysis has been dominantly used for the water resources planning. But, it is more reasonable to explain the variation of spatial and temporal distribution of water by the daily water balance model with daily streamflow data. Since we are recently facing the problems of regional unbalance of water quantity, and of multiuse of irrigation water, and of deterioration of water quality, it is urgently needed to develop the daily water balance model to solve those problems and establish the rational plannings of agricultural water resources. In the circumstances, Daily water Balance(DAWABA) model for irrigation reservoirs was developed and the operation rule of irrigation resorvoir during drought season was established.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.4
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• pp.1389-1400
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• 2013

This study developed an operating rule curve (ORC) for multipurpose water supply (irrigation and environmental water) in heightened agricultural reservoir. Among the 20 reservoirs in improvement project of agricultural reservoir dam heightening, the 4 representative reservoirs (Ungyang, Gungchon, Yongam and Unam) were selected for the study according to the analysis of statistical characteristics. Available environmental water supply amounts during irrigation and non-irrigation periods, which is the range from release restricted water level to high water level were estimated by water balance analysis using reservoir operation model. Reliability, resiliency and vulnerability criteria for water system performance were used to assess the multiple water supply capacity. The ORC was presented as the percentile rank for the daily reservoir water level from the results of reservoir operation using the past couple of decades weather data. The water levels for each percentile were divided into 3 buffer sections representing drought (5~25%), normal (25~75%), and flood (75~95%) year to operate the heightened agricultural reservoir with ORC.

• Journal of The Korean Society of Agricultural Engineers
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• v.63 no.2
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• pp.1-10
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• 2021

Agricultural reservoirs have a great influence on the water circulation in the watershed. It is necessary to evaluate the impact on water circulation by the agricultural reservoir. Therefore, in this study, we simulated the agricultural watershed through linkage of Hydrological Simulation Program Fortran (HSPF) and Module-based hydrologic Analysis for Agricultural watershed (MASA) and evaluated the contribution of the agricultural reservoir to water circulation by watershed water circulation index. As a result of simulating the Idong reservoir watershed through the HSPF-MASA linkage model, the model performance during the validation period was R2 0.74 upstream, 0.78 downstream, and 0.76 reservoir water level, respectively. To evaluate the contribution of agricultural reservoirs, three scenarios (baseline, present state, and present state without reservoir) were simulated, and the water balance differences for each scenario were analyzed. In the evaluation through the agricultural water circulation rate in the watershed, it was found that the water circulation rate increased by 1.1%, and the direct flow rate decreased by 13.6 mm due to the agricultural reservoir. In the evaluation through the Budyko curve, the evaporation index increased by 0.01. Agricultural reservoirs reduce direct runoff and increase evapotranspiration, which has a positive effect on the water circulation.