• Journal of Environmental Science International
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• v.12 no.7
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• pp.745-751
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• 2003

The three-dimensional eco-hydrodynamic model was applied to estimate the physical process in terms of nutrients and net uptake(or regeneration) rate of nutrients in Kamak Bay for scenario analysis to find proper management plan. The estimation results of the physical process in terms of nutrients shelved that transportation of nutrients is dominant in surface level while accumulation of nutrients is dominant in bottom level. In the case of dissolved inorganic nitrogen, the results showed that the net uptake rate was 0∼60 mg/㎡/day in surface level(0∼3m), and the net regeneration rate was 0.0∼10.0 mg/㎡/day in middle level(3∼6m) and above 10mg/㎡/day in bottom level(6m∼below). In the case of dissolved inorganic phosphorus, the net uptake rate was 0.0∼3.0 mg/㎡/day in surface level, and the net regeneration rate was 0.5∼1.5 mg/㎡/day in middle level and 1.0∼3.0 mg/㎡/day in bottom level. These results indicates that net uptake and transport of nutrients are occurred predominantly at the surface level and the net generation and accumulation are dominant at bottom level. Therefore, it is important to consider the re-supplement of nutrients due to regeneration of bottom water.

• Journal of Industrial Technology
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• v.30 no.B
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• pp.83-89
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• 2010

Generally, the accuracy of the prediction of flood elevation is difficult to identify due to the sedimentation on a river bed, earth and sand being moved by flow, and localized torrential downpours caused by climate change. It is also because of natural and artificial influences on rivers. To predict river floodings successfully, more precise and reliable flood elevation prediction system is needed, in which the concentration time of downstream is numerically interpreted through analyzing and utilizing the watermark of the upper region. Therefore, this research analyzed the prediction methods of the changes in water levels, which use the watermarks of the upper region. The watermarks which impacts the spot being predicted of flood was selected through floodgate analysis and correlation analysis. With the selected watermarks, a statistically reliable regression equation was yielded.

• Journal of The Korean Society of Agricultural Engineers
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• v.48 no.1
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• pp.27-38
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• 2006

In this study, we developed a program to estimate discharge efficiently considering major hydraulic characteristic including water level, river bed, water slope and roughness coefficient in a natural river. Stream discharge was measured at Gongju gauge station located in the down stream of the Daechung Dam during normal and dry seasons from 2003 to 2004. The developed model was compared with the results from the existing rating curve at T/M gage stations, and was used for runoff analyses. Evaluating the developed river discharge estimation program, it was applied during 1983-2004 that base flow separation method and RRFS (Rainfall Runoff Forecasting System) which is based on SSARR (Streamflow Synthesis And Resevoir Regulation). The result presents the stage-discharge curve creator range at the Gong-ju is overestimated by approximately $10-20\%$, especially at the low stage. It is attributed to the hydraulic characteristics at the study. The discharge simulated by the RRFS and base flow separation, which is calibrated using the measurement at the early spring and late fall season during relatively d]v season, shows the least errors. The coefficient of roughness at Gongju station varied with the high and low water level.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.24 no.1
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• pp.83-90
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• 2020

A commercial flow measurement radar sensor estimates a quantity of flowed water using surface flow rate. In this way, the amount of water flowing per unit time cannot be measured accurately because of using an estimation result and it can't response environmental changes. For more accurate flow measurements we need width of waterway, water level and distance that water moved per unit time. Commonly two sensors are used to measure water level and flow rate. In this paper, we propose a method to simultaneously measure the water level and surface flow velocity using a single FMCW radar sensor and design the transmission waveform. In order to verify the waveform design, received signal is modelled based on transmission waveform. In addition, we consider phenomenons and problems that may occur in signal processing.

• Journal of the Korean Institute of Rural Architecture
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• v.11 no.2
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• pp.29-36
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• 2009

The recently research shows that the many tourists of Suanbo hot spring waters haven't satisfied the service. These reasons due to that they did not properly consider the satisfaction of tourists' services and index. However, satisfaction level of hot spring waters tourists is interacted complicatedly with various factors, the interactions are not easily identified. A structural equations model is adopted to capture the complex relationships among variables. In the model estimation, we used 140 survey data of Suanbo hot spring waters tourists. The SEM with several factors mentioned above as exogenous variables shows that they have complex and strong relationships. As results of a SEM, it was shown that variables influencing in pleasance are surrounding scenery, clean condition inside hot springs and congestion for use in satisfaction level most. Secondly, in case of kindness, attitudes of employees influence in satisfaction level most, followed by attitudes of residents and kindness of employees. Thirdly, in case of information, it was shown guidance on internal roads influencing in satisfaction level most, followed by guidance on owner drivers, guidance on surrounding tourist attractions and guidance on public transportation. Finally, a variable influencing in accessibility most is satisfaction level of public transportation.

• Journal of Korea Water Resources Association
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• v.51 no.1
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• pp.61-70
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• 2018

This study examined how to determine the optimal sediment level in dam reservoir for efficient plan and operation of dam. Currently, Korea is applying a horizontally accumulated method for sediment level estimation for the safety design of dam and so the method estimated relatively higher level than others. However, the sediment level of dam reservoir should be accurately estimated because it is an important factor in assessing life cycle of a dam. The sediment level in dam reservoir can be determined by SED-2D model linked with RMA-2, horizontally accumulated method, area increment method, and empirical area reduction method. The estimated sediment level from each method was compared with the observed sediment level measured in 2007 in Imha dam reservoir, Korea and then the optimal method was determined. Also, the future sediment level was predicted by each method for the future trend analysis of sediment level. As the results, the most accurate sediment level was estimated by the empirical area reduction method and the future trend of sediment level variation followed the past trend. Therefore, we have found that the empirical area reduction method is a proper one for more accurate estimation of sediment level and it can be validated by the results from a numerical model of SED-2D linked with RMA-2 model.

• Journal of Institute of Control, Robotics and Systems
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• v.2 no.4
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• pp.306-311
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• 1996

This paper discusses the maintenance of the water level of steam generators at its programmed value. The process, the water level of a steam generator, has the nonminimum phase property. So, it causes a reverse dynamics called a swell and shrink phenomenon. This phenomenon is severe in a low power condition below 15 %, in turn makes the start-up of the power plant too difficult. The control algorithm used here incorporates a pole-assignment scheme into the minimum variance strategy and we use a parallel adaptation algorithm for the parameter estimation, which is robust to noises. As a result, the total control system can keep the water level constant during full power by locating closed-loop poles appropriately, although the process has the characteristics of high complexity and nonlinearity. Also, the extra perturbation signals are added to the input signal such that the control system guarantee persistently exciting. In order to confirm the control performance of a proposed pole-assignment self-tuning controller we perform a computer simulation in full power range.

• Proceedings of the Korea Water Resources Association Conference
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• 2023.05a
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• pp.287-287
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• 2023

Surface water-groundwater interaction (SWGI) is an important hydrological process that influences both the quantity and quality of water resources. However, regional scale SWGI model calibration and uncertainty analysis have been a challenge because integrated models inherently carry a vast number of parameters, modeling assumptions, and inputs, potentially leaving little time and budget to explore questions related to model performance and forecasting. In this study, we have proposed the application of iterative ensemble smoother (IES) for uncertainty analysis and calibration of the widely used integrated surface-subsurface model, SWAT-MODFLOW. SWAT-MODFLOW integrates Soil and Water Assessment Tool (SWAT) and a three-dimensional finite difference model (MODFLOW). The model was calibrated using a parameter estimation tool (PEST). The major advantage of the employed IES is that the number of model runs required for the calibration of an ensemble is independent of the number of adjustable parameters. The pilot point approach was followed to calibrate the aquifer parameters, namely hydraulic conductivity, specific storage, and specific yield. The parameter estimation process for the SWAT model focused primarily on surface-related parameters. The uncertainties both in the streamflow and groundwater level were assessed. The work presented provides valuable insights for future endeavors in coupled surface-subsurface modeling, data collection, model development, and informed decision-making.

• Journal of Environmental Science International
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• v.24 no.4
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• pp.437-447
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• 2015

Estimation of runoff peak is needed to assess water availability, in order to support the multifaceted water uses and functions, hence to underscore the modalities for efficient water utilization. The magnitude of storm rainfall acts as a primary input for basin level runoff computation. The rainfall-runoff linkage plays a pivotal role in water resource system management and feasibility level planning for resource distribution. Considering this importance, a case study has been carried out in the Hancheon basin of Jeju Island where distinctive hydrological characteristics are investigated for continuous storm rainfall and high permeable geological features. The study aims to estimate unit hydrograph parameters, peak runoff and peak time of storm rainfalls based on Clark unit hydrograph method. For analyzing observed runoff, five storm rainfall events were selected randomly from recent years' rainfall and HEC-hydrologic modeling system (HMS) model was used for rainfall-runoff data processing. The simulation results showed that the peak runoff varies from 164 to 548 m3/sec and peak time (onset) varies from 8 to 27 hours. A comprehensive relationship between Clark unit hydrograph parameters (time of concentration and storage coefficient) has also been derived in this study. The optimized values of the two parameters were verified by the analysis of variance (ANOVA) and runoff comparison performance were analyzed by root mean square error (RMSE) and Nash-Sutcliffe efficiency (NSE) estimation. After statistical analysis of the Clark parameters significance level was found in 5% and runoff performances were found as 3.97 RMSE and 0.99 NSE, respectively. The calibration and validation results indicated strong coherence of unit hydrograph model responses to the actual situation of historical storm runoff events.

• Journal of Korea Water Resources Association
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• v.53 no.11
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• pp.939-949
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• 2020

Currently, the demand for farmland is steadily decreasing due to changes in the agricultural environment and dietary life. In line with this, the government adopted an integrated water management with the enactment of the Framework Act on Water Management on June 2019. Therefore, it is required to take a closer look at agricultural water demand that accounts for 61% of water use for efficient water resources management. In this study, the overal process was evaluated for estimating agricultural water demand. More specifically, agricultural water demand for paddy field, which comprises 67% to 87% of agricultural water demand, was reviewed in detail. The biggest issue in estimating the paddy field water demand is the selection of the method for potential evapotranspiration. FAO recommends Penman-Monteith, but, currently, our criteria suggest a modified Penman equation that shows over estimation. Also, the crop coefficient, which is the main factor in evaluating evapotranspiration, has an issue that does not consider the current climate and crop varieties because it was developed 23 years ago. Comparing the Modified Penman and Penman-Monteith equations using the data from Jeonju National Weather Service, the modified Penman equation showed a big difference compared to the Penman-Monteith equation. When the crop coefficient was applied, the difference between late May and late August increased, where the amount of evapotranspiration was high. The estimation process was applied to four study reservoirs in Gimje. Comparing the estimated water demand with the supplied water record from reservoirs, the results showed that the estimation accuracy depends on not just the potential evapotranspiration, but also the standard water storing level in paddy fields.