• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.516-516
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• 2022

Agricultural reservoirs are critical water resources structures to ensure continuous water supplies for rice cultivation in Korea. Climate change has increased the risk of reservoir failure by exacerbating discrepancies in upstream runoff generation, downstream irrigation water demands, and evaporation losses. In this study, the variations in water balance components of 400 major reservoirs during 1973-2017 were examined to identify the reservoirs with reliable storage capacities and resilience. A conceptual lumped hydrological model was used to transform the incident rainfall into the inflows entering the reservoirs and the paddy water balance model was used to estimate the irrigation water demand. Historical climate data analysis showed a sharp warming gradient during the last 45 years that was particularly evident in the central and southern regions of the country, which were also the main agricultural areas with high reservoir density. We noted a country-wide progressive increase in average annual cumulative rainfall, but the forcing mechanism of the rainfall increment and its spatial-temporal trends were not fully understood. Climate warming resulted in a significant increase in irrigation water demand, while heavy rains increased runoff generation in the reservoir watersheds. Most reservoirs had reliable storage capacities to meet the demands of a 10-year return frequency drought but the resilience of reservoirs gradually declined over time. This suggests that the recovery time of reservoirs from the failure state had increased which also signifies that the duration of the dry season has been prolonged while the wet season has become shorter and/or more intense. The watershed-irrigated area ratio (W-I_ratio) was critical and the results showed that a slight disruption in reservoir water balance under the influence of future climate change would seriously compromise the performance of reservoirs with W-I_ratio< 5.

• Journal of The Korean Society of Agricultural Engineers
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• v.62 no.6
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• pp.63-72
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• 2020

With the implementation of integrated water management policies, the need for information sharing with respect to agricultural water use has increased, necessitating the quantification of irrigation water supply using monitoring data. This study aims to estimate the irrigation water supply amount based on the relationship between the water level and irrigation canal discharge, and evaluate the reliability of monitoring data for irrigation water supply in terms of hydrology. We conducted a flow survey in a canal and reviewed the applicability of the rating curve based on the exponential and parabolic curves. We evaluated the reliability of the monitoring data using a reservoir water balance analysis and compared the calculated results of the supply quantity in terms of the reservoir water reduction rate. We secured 26 readings of measurement data by varying the water levels within 80% of the canal height through water level control. The exponential rating curve in the irrigation canal was found to be more suitable than the parabolic curve. The irrigation water supplied was less than 9.3-28% of the net irrigation water from 2017 to 2019. Analysis of the reservoir water balance by applying the irrigation water monitoring data revealed that the estimation of the irrigation water supply was reliable. The results of this study are expected to be used in establishing an evaluation process for quantifying the irrigation water supply by using measurement information from irrigation canals in agricultural reservoirs.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2003.10a
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• pp.495-498
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• 2003

In order to analyze water supply capacity in estuary barrage dam, a system was developed in which base model was consisted of daily water balance model and daily inflow model. Agricultural water demand to paddy fields and domestic and industrial water demand were considered in this daily water balance model. Also outflow volume through sluice gate and inside water level at time to start outflow was conditioned initially to simulate reservoir storage. The DAWAST model was selected to simulate daily reservoir inflow in which return flows from agricultural, domestic and industrial water were included to simulate runoff. Using this developed system, water supply capacity in the Keum river estuary reservoir was analyzed.

• Magazine of the Korean Society of Agricultural Engineers
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• v.35 no.4
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• pp.95-105
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• 1993

The purpose of this study is to develop a multireservoir water balance model which may be used to evaluate rural water demands such as agricultural water, domestic water, industrial water and livestock water and to determine effective storage of reservoir. The model was verified to compare the observed reservoir release data with the simulated reservoir release data of the existing Munsan and Dongbu reservoirs located in the Gisan rural district for 3 years('87~'89). For model application, the effective storages of existing reservoirs(Munsan & Dongbu) were evaluated for 10-year frequency drought and that of newly planned reservoirs(Kumbok & Kudong) were determined for 10-year frequency drought. In addition, the behavior of effective storages for existing reservoirs were analyzed in the case of introducing new reservoirs in the existing system.

• Journal of The Korean Society of Agricultural Engineers
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• v.54 no.1
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• pp.93-97
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• 2012

Agricultural water reservoirs upstream of the intake on the basis of the intaking water volume is being made. Therefore, the supply capacity of reservoirs are not considered when the water balance analysis, storm water reservoirs are based on agriculture and further secured by the reservoir water is not used to using natural river water analysis. To overcome these problems can supply reservoirs are available to permit analysis of how much the quantity of water balance analysis, it should be reflected in the line to help. In this study, the natural daily flow data and apply the dimensions of the reservoir, and for more than 30 years of the long-term water balance analysis conducted by Date Youngsan river basin can supply reservoirs are large quantity of permits available is presented.

• Journal of Korean Society on Water Environment
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• v.36 no.6
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• pp.508-520
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• 2020

Dam reservoirs have been reported to contribute significantly to global carbon emissions, but unlike natural lakes, there is considerable uncertainty in calculating carbon emissions due to the complex of emission pathways. In particular, the method of calculating carbon dioxide (CO2) net atmospheric flux (NAF) based on a simple gas exchange theory from sporadic data has limitations in explaining the spatiotemporal variations in the CO2 flux in stratified reservoirs. This study was aimed to analyze the spatial and temporal CO2 distribution and mass balance in Daecheong Reservoir, located in the mid-latitude monsoon climate zone, by applying a two-dimensional hydrodynamic and water quality model (CE-QUAL-W2). Simulation results showed that the Daecheong Reservoir is a heterotrophic system in which CO2 is supersaturated as a whole and releases CO2 to the atmosphere. Spatially, CO2 emissions were greater in the lacustrine zone than in the riverine and transition zones. In terms of time, CO2 emissions changed dynamically according to the temporal stratification structure of the reservoir and temporal variations of algae biomass. CO2 emissions were greater at night than during the day and were seasonally greatest in winter. The CO2 NAF calculated by the CE-QUAL-W2 model and the gas exchange theory showed a similar range, but there was a difference in the point of occurrence of the peak value. The findings provide useful information to improve the quantification of CO2 emissions from reservoirs. In order to reduce the uncertainty in the estimation of reservoir carbon emissions, more precise monitoring in time and space is required.

• Journal of The Korean Society of Agricultural Engineers
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• v.66 no.5
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• pp.29-40
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• 2024

Most agricultural reservoirs were built between the 1940s and 1970s. Therefore, it is necessary to evaluate the current water supply safety, considering changes in water capacity, the water management, and environment in relation to the passage of time.. The design frequency of drought, the number of years areservoir needs to be able to withstand a drought phenomenon, foragricultural water resources in Korea is the 10-year drought. As the water supply system and water supply patterns change, it is necessary to establish a concept of water supply reliability, which refers to the stability of water supply. This study evaluated the water supply reliability of agricultural reservoirs based on the designed frequency. The previously designed frequency and water balance analysis were used to calculate and analyze reservoir storage capacity, water supply turnover, water supply amount, water supply potential, water utilization safety, and water supply reliability. As a result, Yongmyeon Reservoir was found to be stable in terms of water supply reliability, whereas Seongho and Yongpung Reservoirs were found to be unstable using all methods. In particular, when converting the water utilization safety and the water supply reliability to the frequency of drought, Seongho and Yongpung Reservoir were in the lowest class, with a frequency of drought less than four years. Thus, we recommend that the consideration of water supply reliability be included in the preparation of adaptive measures and water supply strategies as changes in environmental conditions continue to develop.

• Korean Journal of Agricultural Science
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• v.35 no.2
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• pp.225-235
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• 2008

The objective of this study is to evaluate the hydrological feasibility of heightening the Dae-ah reservoir in order to save instream flow at the Bong-dong station situated in the Mankyoung river. The results are summarized as follows. Firstly, from the Dong-sang and Dae-ah cascaded reservoir's water balance analysis, water supply indexes of the Dae-ah reservoir were analyzed to have the rate of water supply divided by watershed area of 1207.4 mm, the rate of water supply divided by rainfall of 95.8%, the rate of water supply divided by inflow of 153.1%, the rate of water supply divided by storage capacity of 236.1%, and the rate of inflow divided by storage capacity of 200.6%. Secondly, from the Dae-ah and Kyoung-cheon paralleled reservoir's water balance analysis, flow durations at the Bong-dong station were analyzed to have the Q95 (the 95th high flow) of $28.95m^3/s$, the Q185 (the 185th high flow) of $2.00m^3/s$, the Q275 (the 275th high flow) of $2.00m^3/s$, and the Q355 (the 355th high flow) of $0.82m^3/s$. Thirdly, in case of heightening the full water level of the Dae-ah reservoir of 10m, from the Dong-sang and Dae-ah cascaded reservoir's water balance analysis, water supply indexes of the Dae-ah reservoir were analyzed to have the rate of water supply divided by watershed area of 1220.7 mm, the rate of water supply divided by rainfall of 96.8%, the rate of water supply divided by inflow of 154.6%, the rate of water supply divided by storage capacity of 160.0%, and the rate of inflow divided by storage capacity of 137.0%. Fourthly, in case of heightening the full water level of the Dae-ah reservoir of 10m, from the Dae-ah and Kyoung-cheon paralleled reservoir's water balance analysis, flow durations at the Bong-dong station were analyzed to have the Q95 of $28.09m^3/s$, the Q185 of $1.79m^3/s$, the Q275 of $1.79m^3/s$, and the Q355 of $0.82m^3/s$. The conclusion appeared not to have the hydrological feasibility of heightening the Dae-ah reservoir from the reason that increased storage capacity does not increase water supply amount any more because of the high rate of the water supply divided by inflow.

• Magazine of the Korean Society of Agricultural Engineers
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• v.37 no.2
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• pp.13.2-20
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• 1995

An water balance model was formulated to simulate the change in water levels at the estuary reservoir from sluice gate releases and the inflow hydrographs, and an one-di- mensional flood routing model was formulated to simulate temporal and spatial varia- tions of flood hydrographs along the estuarine river. Flow rates through sluice gates were calibrated with data from the estuary dam, and the results were used for a water balance model, which did a good job in predicting the water level fluctuations. The flood routing model which used the results from two hydrologic models and the water balance model simulated hydrographs that were in close agreement with the observed data. The flood forecasting model was found to be applicable to real-time forecasting of water level fluc- tuations with reasonable accuracies.

• Proceedings of the Korea Water Resources Association Conference
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• 2012.05a
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• pp.221-221
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• 2012

The WRAP-SALT (Water Rights Analysis Package-SALT) simulation includes computation of end-of-month reservoir storage concentrations and mean monthly reservoir outflow concentrations for each month of the simulation. The model computes reservoir storage loads and concentrations based on load balance accounting algorithms and computes concentrations of water released and withdrawn from a reservoir as a function of the volume-weighted mean concentration of the water stored in the reservoir in the current month or previous months. A load budget accounting of the various component load inflows and outflows entering and leaving a reservoir is performed. A time history of storage concentrations computed for previous months is maintained for use in the lag procedure. This study presents computational methods for routing salinity through reservoirs for incorporation into WRAP-SALT simulation routines and methods for determining values for the parameters of the routing methods.