• Nuclear Engineering and Technology
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• v.53 no.11
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• pp.3798-3807
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• 2021

Tritium extraction from radioactively contaminated cement mortar samples was performed using heating and liquid scintillation counting methods. Tritiated water molecules (HTO) can be present in contaminated water along with water molecules (H₂O). Water is one of the primary constituents of cement mortar dough. Therefore, if tritium is present in cement mortar, the buildings and structures using this cement mortar would be contaminated by tritium. The radioactivity level of the materials in the environment exposed to tritium contamination should be determined for their disposal in accordance with the criteria of low-level radioactive waste disposal facility. For our experiments, the cement mortar samples were heated at different temperature conditions using a high-temperature combustion furnace, and the extracted tritium was collected into a 0.1 M nitric acid solution, which was then mixed with a liquid scintillator to be analyzed in a liquid scintillation counter (LSC). The tritium extraction rate from the cement mortar sample was calculated to be 90.91% and 98.54% corresponding to 9 h of heating at temperatures of 200 ℃ and 400 ℃, respectively. The tritium extraction rate was close to 100% at 400 ℃, although the bulk of cement mortar sample was contaminated by tritium.

• Journal of Environmental Impact Assessment
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• v.26 no.6
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• pp.445-456
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• 2017

For impact assessment of inundation in coastal area due to sea level rise (SLR), model for estimating future peak water level was constructed using observed mean sea level (MSL), storm surge level (SSL) data and calculated tide level (TL) data. Based on time series analysis and quadratic polynomial model for SLR and Monte-Carlo simulation for IC, SSL and TL, 100-year return peak water level is expected to be 2.3, 2.6, 2.8m, respectively (each corresponding to year 2050, 2080, 2100). Further analysis on future potential inundation area showed U-dong, Yongho-dong, Songjeong-dong, Jaesong-dong to be at high risk.

• Journal of Environmental Science International
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• v.26 no.10
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• pp.1135-1146
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• 2017

At riverbank filtration sites, groundwater levels of alluvial aquifers near rivers are sensitive to variation in river discharge and pumping quantities. In this study, the groundwater level fluctuation, pumping quantity, and streamflow rate at the site of a riverbank filtration plant, which produces drinking water, in the lower Nakdong River basin, South Korea were interrelated. The relationship between drawdown ratio and river discharge was very strong with a correlation coefficient of 0.96, showing a greater drawdown ratio in the wet season than in the dry season. Autocorrelation and cross-correlation were carried out to characterize groundwater level fluctuation. Autoregressive model analysis of groundwater water level fluctuation led to efficient estimation and prediction of pumping for riverbank filtration in relation to river discharge rates, using simple inputs of river discharge and pumping data, without the need for numerical models that require data regarding several aquifer properties and hydrologic parameters.

• Environmental and Resource Economics Review
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• v.17 no.4
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• pp.875-901
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• 2008

This article estimates the economic values of changes in water quality of the Paldang Watershed by using the Choice Experiment (CE). The conditional logit model estimation results show that a small improvement in water quality from the 'status quo' level to the level of 'very good' increases average household's monthly utility by 3,157 Won, whereas a water quality degradation down to the 'normal' level gives rise to an increase in the monthly average utility by 9,649 Won. The corresponding social gain and loss of water quality changes to the Metropolitan Area were thus estimated about 285 billion Won and 872 billion Won, respectively. This article seems meaningful in that it resorts to the new water ecosystem classification criteria and indices that are respondent-friendly. They help a CE study like this to overcome one of its critical weakness that the number and contents of attributes of a CE study can quickly add to the information overload problem, especially where the environmental good under investigation is hard for ordinary respondents to understand.

• 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.

• Journal of the Korean GEO-environmental Society
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• v.9 no.5
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• pp.21-27
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• 2008

The Sediment deposits in rivers and reservoirs are major components interfering with the useful function of the reservoirs, and clogging the inlet port at water intakes in rivers and erosion of pump impellers. Therefore, an accurate estimation method of sediment deposition is requisite to the efficient water resources investigation, planning and management. The objective of this paper is to forecast of reservoir sediment deposition using two dimensional model (SMS) to UnMun reservoir in GyeongSangBukDo. The RUSLE model showed that reservoirs volume was decreased $2,084.09{\times}10^6m^3$ after 50 years and $2,196.65{\times}10^6m^3$ after 100 years, which is plan flood level elevation (EL.152.12 m) reservoir. The two dimensional model showed that reservoirs volume was decreased $2,227.41{\times}10^6m^3$ after 50 years and $2,121.47{\times}10^6m^3$ after 100 years, which is plan flood level elevation (EL.152.12 m) reservoir. The results of this application showed that the use of two dimensional model was very effective for the estimation sediment deposits throughout the reservoir.

• Journal of The Korean Society of Agricultural Engineers
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• v.52 no.5
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• pp.61-68
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• 2010

Jangchan reservoir is located in Okcheon county, Chungbuk province, of which watershed area is $29.4\;km^2$ from outside, and $5.1\;km^2$ from inside watershed, effective storage capacity is $392{\times}10^4\;m^3$, paddy area to be irrigated is 474 ha. To determine inflows from Keumcheon weir located in outside watershed on an optimum level, a repeated procedure which is composed of simulation of inflows to Keumcheon weir, setting of range of water taking at Keumcheon weir, simulation of inflows to Jangchan reservoir, estimation of paddy water from Jangchan reservoir, and simulation of water storages in Jangchan reservoir was selected. Parameters of DAWAST model for simulating inflows to Jangchan reservoir were determined to UMAX of 315 mm, LMAX of 21 mm, FC of 130 mm, CP of 0.018, and CE of 0.007 with absolute sum of errors in reservoir water storages minimized using unconstrained Simplex method because of no inflows data. Inflows to Keumcheon weir were simulated to $2,132{\times}10^4\;m^3$ on an annual average. Optimal range of water taking at Keumcheon weir to transfer to Jangchan reservoir were $0.81{\sim}50\;mm/km^2/d$, which were summed up to $1,397{\times}10^4\;m^3$ in 66% of total on an annual average. Inflows to Jangchan reservoir were simulated to $1,739{\times}10^4\;m^3$ on an annual average of which were 80 % from Keumcheon weir of outside watershed. Requirements to paddy water from Jangchan reservoir were estimated to $543{\times}10^4\;m^3$ on an annual average.

• Journal of Environmental Impact Assessment
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• v.21 no.1
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• pp.219-227
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• 2012

Daily solar radiation is essential for water resources planning and environmental impact assessment. However, radiation data is not commonly available in Korea other than in big cities, and there has been no direct measurement for rural areas where water resources planning and environmental impact assessment is usually most needed. In general, missing radiation data is estimated from nearby regional stations within a certain distance, and this study compared two dominant methods (modified Angstrom equation and transmittance interpolation method) at six stations in Nakdong River watershed area. Two methods shows a similar level of accuracy but the transmittance interpolation method is likely to be superior in that there is no need for any measurement element since the modified Angstrom equation require the sunshine hour measurement. This study will contribute to improve water resource and water quality management in Nakdong River watershed.

• Proceedings of the Korea Water Resources Association Conference
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• 2023.05a
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• pp.25-25
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• 2023

The ensemble optimal interpolation (EnOI) scheme is a sub-optimal alternative to the ensemble Kalman filter (EnKF) with a reduced computational demand making it potentially more suitable for operational applications. Since only one model is integrated forward instead of an ensemble of model realizations, online estimation of the background error covariance matrix is not possible in the EnOI scheme. In this study, we investigate two Gaussian noise based ensemble generation strategies to produce dynamic covariance matrices for assimilation of water level observations into a distributed hydrological model. In the first approach, spatially correlated noise, sampled from a normal distribution with a fixed fractional error parameter (which controls its standard deviation), is added to the model forecast state vector to prepare the ensembles. In the second method, we use an adaptive error estimation technique based on the innovation diagnostics to estimate this error parameter within the assimilation framework. The results from a real and a set of synthetic experiments indicate that the EnOI scheme can provide better results when an optimal EnKF is not identified, but performs worse than the ensemble filter when the true error characteristics are known. Furthermore, while the adaptive approach is able to reduce the sensitivity to the fractional error parameter affecting the first (non-adaptive) approach, results are usually worse at ungauged locations with the former.

• Journal of the Korean GEO-environmental Society
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• v.16 no.6
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• pp.39-43
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• 2015

This study extends the Distributed Temperature Sensing (DTS) application to delineate the saturated zones in shallow sediment and evaluate the groundwater flow in both downward and upward directions. Dry, partially and fully saturated zones and water level in the subsurface can be recognized from this study. High resolution seepage velocity in vertical direction was estimated from the temperature data in the fully saturated zone. By a single profile, water level can be detected and seepage velocity in saturated zone can be estimated. Furthermore, thermal gradient analysis serves as a new technique to verify unsaturated and saturated zones in the subsurface. The vertical seepage velocity distribution in the recognized saturated zone is then analyzed with improvement of Bredehoeft and Papaopulos' model. This new approach provides promising potential in real-time monitoring of groundwater movement.