• Journal of Korean Tunnelling and Underground Space Association
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• v.15 no.3
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• pp.333-344
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• 2013

This paper discussed about the effect of permeability reduction of the jointed rock mass in the vicinity of a tunnel which is one of the reasons making large difference between the estimated ground-water inflow rate and the measured value. Current practice assumes that the jointed rock mass around a tunnel is a homogeneous, isotropic porous medium with constant permeability. However, in actual condition the permeability of a jointed rock mass varies with the change of effective stress condition around a tunnel, and in turn effective stress condition is affected by the ground water flow in the jointed rock mass around the tunnel. In short time after tunnel excavation, large increase of effective tangential stress around a tunnel due to stress concentration and pore-water pressure drop, and consequently large joint closure followed by significant permeability reduction of jointed rock mass in the vicinity of a tunnel takes place. A significant pore-water pressure drop takes place across this ring zone in the vicinity of a tunnel, and the actual pore-water pressure distribution around a tunnel shows large difference from the value estimated by an analytical solution assuming the jointed rock mass around the tunnel as a homogeneous, isotropic medium. This paper presents the analytical solution estimating pore-water pressure distribution and ground-water inflow rate into a tunnel based on the concept of hydro-mechanically coupled behavior of a jointed rock mass and the solution is verified by numerical analysis.

• Journal of Korea Water Resources Association
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• v.56 no.8
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• pp.485-496
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• 2023

Recently, South Korea has been making efforts to mitigate the risk of water scarcity during droughts by utilizing various drought response measures in dam operations. While various studies have been conducted on this topic, there is currently a lack of research on the economic effects of drought response measures. In this study, we evaluated the economic effects of drought response measures on nationwide multipurpose dams by using a long-term simulated inflow model based on ARIMA and Copula and a dam operation model that reflects drought response measures. The results showed that the expected benefits per unit flow rate were highest for coordinated operation and alternative water supply measures, at KRW 1,176 and KRW 1,139, respectively, while the benefits of emergency water supply utilization and water supply adjustment were estimated at KRW 956 and KRW 875, respectively. Additionally, when we examined the changes in the economic benefits of drought response measures based on the assumption of increased drought severity in the future, the changes in the drought risk resulting from reduced inflow increased the economic benefits of all drought response measures. The economic benefits of water supply adjustment increased by 2.6% compared to the baseline, while the economic benefits of coordinated operation and alternative water supply measures increased by 11.7% compared to the baseline. This suggests that dam-network-based measures, such as coordinated operation and alternative water supply measures, are crucial as drought risk increases. This study is expected to serve as a fundamental reference for selecting and utilizing drought response measures in the future.

• Journal of Korea Water Resources Association
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• v.57 no.1
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• pp.59-72
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• 2024

Agricultural reservoirs supply water for various purposes such as irrigation, maintenance, and living. Since agricultural reservoirs respond sensitively to seasonal and climate changes, it is essential to estimate supply and inflow for efficient operation, and water management should be done based on these data. However, in the case of agricultural reservoirs, the measurement of supply and inflow is relatively insufficient compared to multi-purpose dams, and inflow-supply analysis in agricultural reservoirs through water balance analysis is necessary for efficient water management. Therefore, rainfall-runoff analysis models such as ONE model and Tank model have been developed and used for reservoir water balance analysis, but the applicability analysis for ungauged watersheds is insufficient. The ONE model is designed for daily runoff calculation, and the model has one parameter, which is advantageous for calibration and ungauged watershed analysis. In this study, the water balance was analyzed through the ONE model and the Tank model for 15 watersheds upstream of dams, and R² and NSE were used to quantitatively compare the performance of the two models. The simulation results show that the ONE model is suitable for predicting the inflow of agricultural reservoirs with the ungauged watershed

• Analytical Science and Technology
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• v.32 no.2
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• pp.65-76
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• 2019

Despite the expansion of sewage treatment facilities to reduce pollutants in the tributaries of the Han River, water pollution accidents such as fish deaths continue to frequently occur. The purpose of this study was to identify the pollutant sources using water quality and stable isotope ratio (${\delta}^{15}N$, ${\delta}^{13}C$, ${\delta}^{15}N-NH_4$, ${\delta}^{15}N-NO_3$) analysis results in the three inflow tributaries (Gulpocheon (GP), Anyangcheon (AY) and Sincheon (SC)) of the Han River. Water quality was analyzed in June and October from 2013 to 2017, and the results showed that the concentrations of nutrients, such as T-N, $NO_3-N$, and T-P, were increased at GP4, AY3, SC3, and SC4, which lie downstream of sewage treatment facilities. The results of ${\delta}^{15}N$ for June 2017 indicated that the source of nitrogen was sewage or livestock excreta at GP4 and SC4, and organic fertilizers at AY3 and SC3. ${\delta}^{15}N-NO_3$ results suggested that the source of nitrogen was related to organic sewage, livestock or manure at GP4, AY3 and SC4. Therefore, GP4 and SC4 were more influenced by effluent from sewage treatment facilities than by their tributaries, AY3 and SC3 were considered to be influenced more by their tributary than effluent from sewage treatment facilities. With the results of this study, the source of contamination (sewage treatment facility effluent) of river inflow downstream of Han River could be confirmed using water quality and stable isotope ratio.

• Proceedings of the SAREK Conference
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• 2006.06a
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• pp.607-612
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• 2006

A pressure-type rapid automatic filter of 2000mm diameter and 170 ton/h filtering capacity was fabricated. In case of no external impurity inflow, the turbidity removal efficiency on raw water was experimented and the numbers of impurities of each sizes were analyzed by particle counter. As the result of circulated filtering, the raw water of 40 NTU was filtered to 0.44 NTU and the numbers of impurities above $1{\mu}m$ were removed by approximately 95%. With the filtering efficiency experimented and the mathematical method, the turbidity change of circulation water were calculated according to the inflow rate of external impurity and water treatment method of blow-down or filtering. The cost of blow-down water was calculated from above results. And simple payback period for this filter is calculated as about one year. Nowadays, as the cost of water is continuously increasing and environment regulations will be more strict, the water quality control using this filter will be expected to satisfy the user requirement.

• Journal of the Korean Society of Industry Convergence
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• v.22 no.2
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• pp.173-181
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• 2019

This study was carried out numerically to investigate the flow characteristics in the Venturi tube with $90^{\circ}$ T-branch tube and the inflow of condensed water into the Venturi tube from the branch tube. In this study, the diameter of the branch tube(1, 2, 3mm) and the neck diameter of the Venturi tube(0.3, 0.9, 1.5mm) were varied. The flow rate of the water at the Venturi tube inlet is 80cc/min and the water temperature is 288K. The condensed water temperature at the branch tube inlet is 355K. It was found that the velocity and pressure of the fluid near the branch point in the Venturi tube were more dependent on the diameter of the Venturi tube than the diameter of the branch tube. The temperature of the mixed water at the exit of the Venturi tube was the highest when the Venturi tube's neck diameter is 0.9mm and the branch tube diameter is 2mm. This means that the condensed water is flowing well through the branch tube.

• Journal of Environmental Science International
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• v.17 no.4
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• pp.451-459
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• 2008

This study was carried out forecasting of pollution inflow of the Small Mountainous Catchment, namely; Seolma-cheon experimental catchment. Pollutographs of DO, BOD, T-N, Conductivity, T-p, pH. COD, SS from this catchment were obtained from in-situ data of total ten events using QUAL2E-PULS model. From the analysis results, between up stream(Sabang-bridge) and down stream (Memorial-bridge, outlet) obtained relation formula of water quality component. Determination coefficient of relation formula, Conductivity, COD, BOD, DO, pH, T-N, T-P, and SS showed high relation of $0.87{\sim}0.99$. The increases of DO, BOD, COD, and pH concentration of Memorial-bridge were associated with pollution inflow by road building far 2.25km from Sabang-bridge to down stream. The analysis results of QUAL2E-PULS simulation and up/down stream relation formula, pollution amounts of DO, BOD, COD and pH increased at Memorial-bridge and pollution source site. Therefore, pollution inflow can be forecasted exactly by up/down stream relation formula at pollution source site.

• Journal of Soil and Groundwater Environment
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• v.27 no.3
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• pp.1-10
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• 2022

Most wells developed in Jeju island before the enactment of the Groundwater Management Ordinance in 2002 are vulnerable to aquifer contamination due to inflow of upper groundwater having the high concentration of nitrate nitrogen, likely due to incomplete grouting in upper section of the wells. Although these wells require entire reinstallation, it is often necessary to rehabilitate the existing wells due to various constraints. Therefore, to identified the inflow section of contaminants, the thermal level sensor (TLS) technique was firstly applied for three wells, which enables to monitor temperature variations in every 50 cm depth. Then, the grouting material was injected to the upper section to prevent the inflow of upper contaminated groundwater into the entire aquifer. By applying TLS technique, it was found that the temperature deviations in the upper groundwater inflow section decreased sharply. Moreover, both the change in the concentration of nitrate nitrogen in the rainy/dry seasons and the average concentrations were found to decrease rapidly after grouting material injection. Consequently, the application of TLS proposed in the study turned out to be appropriate to prevent aquifer contamination.

• Nuclear Engineering and Technology
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• v.55 no.4
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• pp.1310-1323
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• 2023

A reactor coolant pump (RCP) is essential for transporting coolant in the primary loop of pressurized water reactors. In the advanced passive reactor, the absence of a long pipeline between the steam generator and RCP serves as a transition section, resulting in a non-uniform flow field at the pump inlet. Therefore, the characteristics of the pump should be investigated under non-uniform flow to determine its influence on the pump. In this study, the pressure pulsation characteristics were examined in the time and frequency domains, and the sources of low-frequency and high-amplitude signals were analyzed using wavelet coherence analysis and numerical simulation. From computational fluid dynamics (CFD) results, non-uniform inflow has a great effect on the flow structures in the pump's inlet. The pressure pulsation in the pump at the rated flow increased by 78-128.7% under the non-uniform inflow condition in comparison with that observed under the uniform inflow condition. Furthermore, a low-frequency signal with a high amplitude was observed, whose energy increased significantly under non-uniform flow. The wavelet coherence and CFD analysis verified that the source of this signal was the low-frequency pulsating vortex under the steam generator.

• Journal of Korea Water Resources Association
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• v.41 no.12
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• pp.1219-1230
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• 2008

Stream inflows induced by flood runoffs have a higher density than the ambient reservoir water because of a lower water temperature and elevated suspended sediment(SS) concentration. As the propagation of density currents that formed by density difference between inflow and ambient water affects reservoir water quality and ecosystem, an understanding of reservoir density current is essential for an optimization of filed monitoring, analysis and forecast of SS and nutrient transport, and their proper management and control. This study was aimed to quantify the characteristics of inflow density current including plunge depth($d_p$) and distance($X_p$), separation depth($d_s$), interflow thickness($h_i$), arrival time to dam($t_a$), reduction ratio(${\beta}$) of SS contained stream inflow for different flood magnitude in Daecheong Reservoir with a validated two-dimensional(2D) numerical model. 10 different flood scenarios corresponding to inflow densimetric Froude number($Fr_i$) range from 0.920 to 9.205 were set up based on the hydrograph obtained from June 13 to July 3, 2004. A fully developed stratification condition was assumed as an initial water temperature profile. Higher $Fr_i$(inertia-to-buoyancy ratio) resulted in a greater $d_p,\;X_p,\;d_s,\;h_i$, and faster propagation of interflow, while the effect of reservoir geometry on these characteristics was significant. The Hebbert equation that estimates $d_p$ assuming steady-state flow condition with triangular cross section substantially over-estimated the $d_p$ because it does not consider the spatial variation of reservoir geometry and water surface changes during flood events. The ${\beta}$ values between inflow and dam sites were decreased as $Fr_i$ increased, but reversed after $Fr_i$>9.0 because of turbulent mixing effect. The results provides a practical and effective prediction measures for reservoir operators to first capture the behavior of turbidity inflow.