• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2002.10a
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• pp.45-50
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• 2002

This study presents a modeling method to predict fate of resuspended sediment in the development of deep-sea mineral resources. Resuspended deep-sea sediment during the development is considered a major environmental problem. In order to quantitatively analyze the resuspended sediment in the water column, particle size distribution (PSD) is considered an important factor. The model developed here includes PSD and coagulation process, as well as sedimentation process. Using the model, basic simulation was performed under representative environmental setting. The simulation showed the dynamics of change of particle size distribution for 50 m depth of water column up to 10 days of simulation time. Coagulation seemed an important factor in the fate of resuspended deep-sea sediment.

• Proceedings of the Korea Water Resources Association Conference
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• 2023.05a
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• pp.274-274
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• 2023

기후변화의 영향으로 겨울철 적설의 양상이 과거와는 많이 달라진 것으로 보인다. 따라서 미래의 적설이 어떤 확률로 발생할 것인지도 과거에 비해 많이 달라질 것으로 예상된다. 하지만 어떤 정도로 달라질 것인지는 정확하게 알 수가 없다. 본 연구에서는 이를 합리적으로 추정하기 위해 일본에서 수행한 대규모 기후 앙상블 모의실험 결과로 생성된 d4PDF(Data for Policy Decision Making for Future Change) 자료 중 적설과 기온 자료를 이용하여 일 최심적설심을 모의하고 연최대치계열을 작성하여 과거의 최심적설심 연최대치분포와 비교하여 분위사상법을 통해 모형의 오차를 보정한 후 미래 지구평균온도 상승 시의 기후모의 결과에 적용함으로써 지구평균온도 상승 정도에 따라 우리나라의 적설양상과 확률적설심이 어떻게 변화할 것인지 추정해 보았다. 연구의 결과는 미래 적설과 관련된 설계와 방재 목적에 참고적으로 활용될 수 있을 것이다.

• Journal of Korean Society of Environmental Engineers
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• v.31 no.9
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• pp.817-824
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• 2009

To prevent turbidity breakthrough in a depth filter caused by hydraulic shock loads, influence of turbidity and particle number in filtrate by variation of operating filter number depending on inflow change was investigated. Inflow quantity at the S water treatment plant (WTP) was varied and ratio of maximum/minimum inflow quantity was 2.2, therefore filtration velocity was also subsequently changed. The S WTP changed operating filter number depending on inflow variation to minimize change of filtration velocity. Particle breakthrough was not severe when operation system was changed, out-of-operation and re-start of filter was repeated depending on inflow quantity. Slight particle breakthrough was noticed when re-start of filter was implemented at the filter that had a cumulative filtration run time of less than 10 h or more than 50 h. This can be attributed to the inadequate ripening and over accumulation of particles on media. Therefore, it is more efficient to choose a re-starting filter basin which has cumulative filtration run time more than 10 h or less than 50 h to reduce particle breakthrough. Filter number variation depending on inflow change was proven to be a method for improvement of unit filter run volume (UFRV).

• Magazine of the Korean Society of Agricultural Engineers
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• v.12 no.3
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• pp.2029-2034
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• 1970

This research was attempted to study on the effects of desalinization by the depth and interval of open conduit in Kang-Hwa polder where is located at the Kil-sang Myun, Kang-Hwa Gun, Kyung-gi Do, and it has been continued for the three years from 1967 to 1969. The results obtained are as follows; 1. The depths of saline expulsion by supplying of irrigation water are approximately 30cm to 50cm under the ground surface, but saline expulsion is hardly done in case of the depth which is deeper than the above mentioned, because the moisture and saline content hardly change in such a condition. 2. The speed of vertical percolation gradually decreases below the 30cm depth, but it is noticed that there is a tendency to make the percolation of the horizental direction from its layer in Kang-Hwa reclaimed tidal land. 3. Comparing experimental treatments-varing depths and intervals of open conduits, the interval of open conduit has a more effect upon the promotion of desalinization and increasing of the rice yields than the depth of it. Therefore, according to the results of experimental data, the optimum depth of open conduit is about 0.9m, the effective interval of it is about 18m. 4. Considering the loss of arable area by the layout of open conduit, the reasonable interval of it could extend to 36m.

• Journal of the Korean earth science society
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• v.33 no.1
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• pp.49-58
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• 2012

Through a statistical change-point analysis, this study found that Korea landfalling tropical cyclone (TC) frequency has increased rapidly since 1981. This increase is due to the following phenomenon. When anomalous cyclone is developed in the East Asian continent, anomalous anticyclone is reinforced in the western Pacific, which is related to the eastward shift of western North Pacific high, and thus anomalous southerly is formed to Korea from low-latitudes. This anomalous southerly plays an important role as steering flow in moving TCs toward Korea. To examine the cause of the development of anomalous cyclone in the East Asian continent, this study analyzed the water equivalent of accumulated snow depth during the preceding spring (March to May). As a result, less snow depth is observed in most regions of the East Asian continent than before 1981. Therefore, anomalous cyclone in the East Asian continent in summer can be reinforced by the land heating from the preceding spring and then the steering flow of anomalous southerly that moves TCs toward Korea can be also developed to Korea from low-latitudes in summer.

• Journal of the Korean Society of Marine Environment & Safety
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• v.16 no.3
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• pp.259-268
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• 2010

Data on squid catches by the Korean jig fishery in sea blocks ($30'{\times}30'$), water temperatures at depth(30m, 50m and 100m) and zooplankton biomass in the East Sea from 1980 to 1999 were analyzed to examine the mechanism of formation of the high density stock area. Japanese common squid (Todarodes pacificus) catch in the East Sea was low in 1980s, while the catch was high in 1990s. The five sea blocks (No. 76, 82, 83, 87, 88) of the southern part in the eastern coastal waters of Korea showed high levels of percentage of total catch (35.1%), whereas the four sea blocks (No. 65, 71, 72, 78) of the coastal waters of Uleung Island showed high levels of percentage of CPUE (61.2%) for 20 years. Squid catches showed monthly fluctuations according to the vertical distribution of optimum water temperature for fishing ($14^{\circ}C{\sim}19^{\circ}C$). High total catch and high CPUE area matched well with $10^{\circ}C$ isothermal lines at 100m depth indicating northern limiting of Tsushima Warm Current, and temporal and spatial change in $10^{\circ}C$ isothermal line caused the change in total catch and CPUE. Horizontal distribution of zooplankton biomass by sea block was not matched well with those of total catch and CPUE, however pattern of time-series change in total zooplankton biomass was similar to that in total squid catch.

• Journal of Soil and Groundwater Environment
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• v.13 no.1
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• pp.77-91
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• 2008

In this study, we developed a technique of applying DRASTIC, which is the most widely used tool for estimation of groundwater vulnerability to the aqueous phase contaminant infiltrated from the surface, and a groundwater flow model jointly to assess groundwater contamination potential. The developed technique is then applied to Buyeo-eup area in Buyeo-gun, Chungcheongnam-do, Korea. The input thematic data of a depth to water required in DRASTIC model is known to be the most sensitive to the output while only a few observations at a few time schedules are generally available. To overcome this practical shortcoming, both steady-state and transient groundwater level distributions are simulated using a finite difference numerical model, MODFLOW. In the application for the assessment of groundwater vulnerability, it is found that the vulnerability results from the numerical simulation of a groundwater level is much more practical compared to cokriging methods. Those advantages are, first, the results from the simulation enable a practitioner to see the temporally comprehensive vulnerabilities. The second merit of the technique is that the method considers wide variety of engaging data such as field-observed hydrogeologic parameters as well as geographic relief. The depth to water generated through geostatistical methods in the conventional method is unable to incorporate temporally variable data, that is, the seasonal variation of a recharge rate. As a result, we found that the vulnerability out of both the geostatistical method and the steady-state groundwater flow simulation are in similar patterns. By applying the transient simulation results to DRASTIC model, we also found that the vulnerability shows sharp seasonal variation due to the change of groundwater recharge. The change of the vulnerability is found to be most peculiar during summer with the highest recharge rate and winter with the lowest. Our research indicates that numerical modeling can be a useful tool for temporal as well as spatial interpolation of the depth to water when the number of the observed data is inadequate for the vulnerability assessments through the conventional techniques.

• Journal of the Korean Geosynthetics Society
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• v.17 no.1
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• pp.21-31
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• 2018

This paper analyzes the displacements of CFRD which was completed by field measurement. It is to understand the deformation behavior of the dam body according to the water level change from the impounding time. And it was compared with numerical analysis results. As a result of measuring the behavior of the dam crest and downstream slope according to impounding, horizontal displacements in axis direction of the dam, upstream and downstream displacements and settlements occurred mostly when the water level reaches about half of the dam height. The displacements continued until the water level reached its maximum. After that, it showed a constant convergence regardless of the water level. Horizontal displacements of the face slab which is the most important in CFRD were similar at all locations. The Horizontal displacements of the face slab showed the trends of increasing in winter and decreasing in summer due to the effect of the outside temperature before impounding. Also, the displacements increased until the water level reached about half of the dam height. After that, they decreased with rising in water level. As a result, the face slab behaviors according to seasonal change after impounding as well as water level condition. It is judged because of the material characteristics of the concrete slab. Numerical analysis showed slightly different maximum settlement and depth of occurrence from the measuring data after construction of the dam. It is considered that this is due to various design and construction differences such as the estimation of input parameters in analysis, construction period, and the layer thickness of construction. For the overall period of the dam, the settlements were mostly completed during the construction period and some settlements occurred in the early days of impounding and then converged.

• Proceedings of the KSRS Conference
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• v.1
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• pp.21-24
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• 2006

Processes controlling the interannual variation of mixed layer temperature (MLT) averaged over the NINO3 domain ($150-90^{\circ}W$, $5^{\circ}N-5^{\circ}S$) are studied using an ocean data assimilation product that covers the period of 1993 to 2003. Advective tendencies are estimated here as the temperature fluxes through the domain's boundaries, with the boundary temperature referenced to the domain-averaged temperature to remove the dependence on temperature scale. The overall balance is such that surface heat flux opposes the MLT change but horizontal advection and subsurface processes assist the change. The zonal advective tendency is caused primarily by large-scale advection of warm-pool water through the western boundary of the domain. The meridional advective tendency is contributed mostly by Ekman current advecting large-scale temperature anomalies though the southern boundary of the domain. Unlike many previous studies, we explicitly evaluate the subsurface processes that consist of vertical mixing and entrainment. In particular, a rigorous method to estimate entrainment allows an exact budget closure. The vertical mixing across the mixed layer (ML) base has a contribution in phase with the MLT change. The entrainment tendency due to temporal change in ML depth is negligible comparing to other subsurface processes. The entrainment tendency by vertical advection across the ML base is dominated by large-scale changes in wind-driven upwelling and temperature of upwelling water. Tropical instability waves (TIWs) result in smaller-scale vertical advection that warms the domain during La Ni? cooling events. When the advective tendencies are evaluated by spatially averaging the conventional local advective tendencies of temperature, the apparent effects of currents with spatial scales smaller than the domain (such as TIWs) become very important as they redistribute heat within the NINO3 domain. However, such internal redistribution of heat does not represent external processes that control the domain-averaged MLT.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.137-137
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• 2021

In this study we aimed to enhance streamflow prediction skill of a land-surface hydrological model, WRF-Hydro, over one of the snow dominated catchments lies in Himalayan mountainous range, Astore. To assess the response of the Himalayan river flows to climate change is complex due to multiple contributors: precipitation, snow, and glacier melt. WRF-Hydro model with default glacier module lacks generating streamflow in summer period but recently developed WRF-Hydro-CROCUS model overcomes this issue by melting snow/ice from the glaciers. We showed that by implementing WRF-Hydro-CROCUS model over Astore the results were significantly improved in comparison to WRF-Hydro with default glacier module. To constraint the model with the observed streamflow we chose 17 sensitive parameters of WRF-Hydro, which include groundwater parameters, surface runoff parameters, channel parameters, soil parameters, vegetation parameters and snowmelt parameters. We used Dynamically Dimensioned Search (DDS) method to calibrate the daily streamflow with the Nash-Sutcliffe efficiency (NSE) being greater than 0.7 both in calibration (2009-2010) and validation (2011-2013) period. Based on the number of iterations per parameter, we found that the parameters related to channel and runoff process are most sensitive to streamflow. The attempts to address the responses of the streamflows to climate change are still very weak and vague especially northwest Himalayan Part of Pakistan and this study is one of a few successful applications of process-based land-surface hydrologic model over this mountainous region of UIB that can be utilized to have an in-depth understanding of hydrological responses of climate change.