• Journal of Korea Water Resources Association
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• v.54 no.6
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• pp.443-452
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• 2021

The authors obtained the discrete hedging rule for a reservoir's water supply operation by applying mixed-integer programming to save more water by earlier rationing of water supply for a drought period. The 'water supply adjustment guide' is the current operational method applied to the multipurpose reservoirs, and it was derived by a simulation method. Applying the two rules to the Hapcheon multipurpose dam's reservoir simulations with the inflow record from 2003 to 2018, the water supply deficit occurred for the long drought from 2015 to 2018. Especially, the no water supply or intermittent water supply persisted for the second half of 2017. The water supply adjustment guide had the 'normal water supply recovery threshold on storage,' which resulted in the water supply being unavailable in July 2017; then, the water supply suspension occurred until January 2018, when the reservoir storage was greater than the normal water supply recovery threshold. Despite the storage increasing due to the inflow of water into the reservoir, the suspension occurrence needs to be improved in practice. The current water supply adjustment guide and the discrete hedging rule for a reservoir's water supply operation are useful and realistic as the reservoir operation guide, which shows the concept of reducing water supply during the drought phase as scientific figures. However, to improve the reservoir simulation results, which do not provide any or intermittent water for several months, it is necessary to increase the current water supply reduction for drought phases.

• Magazine of the Korean Society of Agricultural Engineers
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• v.32 no.3
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• pp.31-38
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• 1990

The power water flowed out from the multipurpose darn influences the ecosystem approximately because of the low water temperature. An appropriate counter measure to the rising water temperature is needed for growing crops especially when the temperature is below 18˚C in the source of the irrigation water This observational study is practiced in Yong-Doo water warming canal and pond in the down stream of Choong-Ju multipurpose dam and is practiced for analyse and compare the rising effects in actural water temperature by actual measurement with the rising effects of planned water temperatuer by the basic theoritical method and for the help to present the direction in plan establishment through investigate the results afterwards. The results are as follows. 1.The degree of the rise of the water temperature can be decided by $\theta$x=$\theta$o +K L--v.h (T-$\theta$˚)Then, K values of a factor representing the characteristics of the water warming canal were 0.00002043 for the type I. and 0.0000173 for the type II. respectively. 2.A variation of water temperature which produced by the difference effective temperature and water temperature in the water warming canal was $\theta$x1 = 16.5 + 15.9(1-e -0.00018x), $\theta$x2 =18.8 + 8.4( 1-e -0.000298x)for the type I. and $\theta$x, = 19.6 + 12.8 ( 1-e -0.00041x) for the type II. 3.It was shown that the effects of the rise of water temperature for the type I. water warming canal were greater than that of type II. as a resultes of broadening the surface of the canal compared with the depth of water, coloring the surface of water canal and installing the resistance block. 4.In case of the type I. water warming canal, the equation between the air temperature and the degree of the rise of water temprature could be made ;Y= 0.4134X + 7.728 In addition, in case of the type II. water warming canal, the correlation was very low. 5.A monthly variation of the water temperature in the water warming canal was the highest in August during the irrigation period and the water temperature rose with the air temperature until August. However, it was blunted after then. 6.A rising degree of water temperature of the practical value in the water warming pond was higher than that of the theoritical equation by 69% for the type I. and 57% for the type II. Accordingly, it was possible to acquire the result near the practical value.$\theta$w-$\theta$o=[1-exp{ -h(1+2$\psi$) . X($\theta$w-$\theta$0)XC Here, C values are 1.69 for the type I. and 1.57 for the type II. 7.It was shown that the effect of the rise of water temperature was favorable when the thermal absorption was to be good by coloring the surface of the water warming pond and removing the bottom osmosis. 8.By enlarging the surface of water in comparison with the depth, and by having dead area of water in the water warming pond, this structure in the water warming pond is helpful for the rise of water temperature.

• New & Renewable Energy
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• v.16 no.1
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• pp.47-57
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• 2020

In Floating PV (Photovoltaic) systems, PV modules are installed on water by utilizing the surface of idle water such as a reservoir and multipurpose dam. A floating PV system, therefore, has the advantage of efficiency in national land use and improved energy yield owing to cooling effect compared to on-land PV systems. Owing to the limitation of installation environment for a floating PV system, the system, however, has the disadvantage of an increase in transmission distance of DC (Direct current) cables. A longer transmission distance of a DC cable results in greater power loss due to a voltage drop. This leads to a decline in economic feasibility for the floating PV system. In this paper, the economic analysis for 10 floating PV systems installed in a reservoir has been conducted in terms of a change in annual power sales according to the variation of transmission losses depending on the factors affecting the voltage drop, such as transmission distance, cross-section area of underwater cable, the presence of joint box, and PV capacity.

• Korean Journal of Ecology and Environment
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• v.44 no.3
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• pp.264-271
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• 2011

At the Jangheung multipurpose dam, which is on the Tamjin River, a trapping and trucking operation was established to maintain continuous upstream migration of fish,. To facilitate fish gathering, installation of an effective fishing trap was required. In this study, we evaluated the fish trap, established at the Jangheung dam, using PIT (Passive Integrated Transponder) telemetry. A total of 254 individuals from 15 species were monitored. Among these tagged species, 36 individuals from 6 species (Carassius auratus, C. cuvieri, Zacco temminckii, Z. platypus, Pungtungia herzi, and Pseudobagrus koreanus) were detected; a 14.2% detection rate. C. auratus recorded the highest detection rate of 44.2% while P. herzi was 14.3%. Z. temminckii and Z. platypus showed relatively low detection, 5% and 7.7% respectively. Some of individuals from C. auratus and Z. platypus did not pass through the antenna at the first attempt but were continuously detected on multiple days. There were no statistical differences in body size (total length, standard length and body weight) of individuals that did or did not swim into the trap (Mann-Whitney U test, p>0.05). Fish mainly swam into the trap during outflow of water from the dam (Mann-Whitney U test, p<0.001) and showed a higher detection frequency in daytime than nighttime (Mann-Whitney U test, p<0.001). Thus, for fish movement into the trap, external factors such as outflow from dam and time of day have important roles. Based on detection rate, not all fishes showed upstream migration but represented selective migration. Consequently, the establishment of flexible outflow strategies that take into consideration ecological characteristics of fishes should required for improving the efficiency of fishway.

• The Journal of Engineering Geology
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• v.20 no.2
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• pp.147-153
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• 2010

Cut-off wall with a low permeability can be constructed to prevent groundwater seepage in spillway tunnel areas. Three spillway tunnels are constructed in Im-ha multipurpose dam region and three types of cut-off walls with a variety of directions and scales are designed. As a result of MODFLOW modeling to assess the effect of cut-off wall for three types, groundwater inflows to the tunnels range from 64.26 $m^3/day$ to 65.49 $m^3/day$ and also they through a cut-off wall section from a reservoir do from 44.08 $m^3/day$ to 45.31 $m^3/day$ and it does not show any significant difference among them. Therefore, a construction process and an environmental conservation rather than the effectiveness of cut-off wall need to be considered to select the best cut-off wall in this region.

• Water Engineering Research
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• v.3 no.1
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• pp.57-62
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• 2002

This research is intended to integrate long-term operation rules and real time operation policy for conservation & flood control in a reservoir. The familiar Yield model has been modified and used to provide long-term rule curves. The model employs linear programming technique under given physical conditions, i.e., total capacity, dead storage, spillways, outlet capacity and their respective elevations to find required and desired minimum storage fur different demands. To investigate the system behavior resulting from the above-mentioned operating policy, i.e., the rule curves, the simulation model was used. Results of the simulation model show that the results of the optimization model are indeed valid. After confirmation of the above mentioned rule curves by the simulation models, gate operation procedure was merged with the long term operation rules to determine the optimum reservoir operating policy. In the gate operation procedure, operating policy in downstream flood plain, i.e., determination of damaging and non-damaging discharges in flood plain, peak floods, which could be routed by reservoir, are determined. Also outflow hydrograph and variations of water surface levels for two known hydrographs are determined. To examine efficiency of the above-mentioned models and their ability in determining the optimum operation policy, Esteghlal reservoir in Iran was analyzed as a case study. A numerical model fur the solution of two-dimensional dam break problems using fractional step method is developed on unstructured grid. The model is based on second-order Weighted Averaged Flux(WAF) scheme with HLLC approximate Riemann solver. To control the nonphysical oscillations associated with second-order accuracy, TVD scheme with SUPERBEE limiter is used. The developed model is verified by comparing the computational solutions with analytic solutions in idealized test cases. Very good agreements have been achieved in the verifications.

• Journal of Environmental Science International
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• v.19 no.1
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• pp.39-45
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• 2010

When the Juam multipurpose dam which is connected with existing large water supply facilities is finished, water environment is changed from stream to lake. The changed quality of water should be examined. In this study, the result of water quality forecasting is analysed and an effective management plan of water quality is presented. Tn this study, the WASPS model that is a dynamic water quality simulation model was selected to forecast the water quality. This model forecasts movement of change of pollutants. For an application of the model, the subject areas were divided into seventeen sub-areas by considering change temperature depending measuring points and on depth of water. Meteorological data collected by the meteorological observatory and data about quality measured by the Korea Water Resources Development Corporation were used for an operation of the model. As a result of quality examination through quality data and estimated pollutant loading, the water quality environment criterion was grade II and the nutritive condition was measured as meso-graphic grade. In this study, an effective management was planned to improve water quality by reducing pollution load. According to the result of examination, when more than 30% of BOD was reduced it was recorded that the environment standard of water quality was improved to the second grade.

• Journal of Korea Water Resources Association
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• v.35 no.6
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• pp.797-805
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• 2002

The EV ROM, a joint reservoir operation model for flood control that accounts for the downstream flow condition, has been introduced in the preceding article (Shin et al, 2000). A joint reservoir operation model computer program for the Geum river basin, developed by FORTRAN Power Station 4.0 using the EV ROM, is hereby presented. Three case studies of flood control by joint operation of the Yongdam and Daechung Multipurpose Dams in the Geum river basin revealed that the performance of the EV ROM was superior to the existing Rigid ROM and Technical ROM. This is because the EV ROM can account for the downstream flow condition as well as the upstream inflow and the reservoir water level. In order to apply for various floods events in the future, consistent improvement of the developed EV ROM and efforts for more accurate rainfall prediction are required.

• Journal of Korea Water Resources Association
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• v.48 no.7
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• pp.567-579
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• 2015

This study performed the non-stationary flood frequency analysis considering time-varying parameters of a probability density function. Also, return period and risk under non-stationary condition were estimated. A stationary model and three non-stationary models using Generalized Extreme Value(GEV) were developed. The only location parameter was assumed as time-varying parameter in the first model. In second model, the only scale parameter was assumed as time-varying parameter. Finally, the both parameters were assumed as time varying parameter in the last model. Relative likelihood ratio test and Akaike information criterion were used to select appropriate model. The suggested procedure in this study was applied to eight multipurpose dams in South Korea. Using relative likelihood ratio test and Akaike information criterion it is shown that the inflow into the Hapcheon dam and the Seomjingang dam were suitable for non-stationary GEV model but the other six dams were suitable for stationary GEV model. Also, it is shown that the estimated return period under non-stationary condition was shorter than those estimated under stationary condition.

• Journal of Korean Society for Geospatial Information Science
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• v.16 no.1
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• pp.23-32
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• 2008

According to recent frequent local flash flood due to climate change, the very short-term rainfall forecast using remotely sensed rainfall like radar is necessary to establish. This research is to evaluate the feasibility of GIS-based distributed model coupled with radar rainfall, which can express temporal and spatial distribution, for multipurpose dam operation during flood season. $Vflo^{TM}$ model was used as physically based distributed hydrologic model. The study area was Yongdam dam basin ($930\;km^2$) and the 3 storm events of local convective rainfall in August 2005, and the typhoon.Ewiniar.and.Bilis.collected from Jindo radar was adopted for runoff simulation. Distributed rainfall consistent with hydrologic model grid resolution was generated by using K-RainVieux, pre-processor program for radar rainfall. The local bias correction for original radar rainfall shows reasonable results of which the percent error from the gauge observation is less than 2% and the bias value is $0.886{\sim}0.908$. The parameters for the $Vflo^{TM}$ were estimated from basic GIS data such as DEM, land cover and soil map. As a result of the 3 events of multiple peak hydrographs, the bias of total accumulated runoff and peak flow is less than 20%, which can provide a reasonable base for building operational real-time short-term rainfall-runoff forecast system.