• Proceedings of the Korea Water Resources Association Conference
• /
• 2005.05b
• /
• pp.1184-1188
• /
• 2005

The impacts of turbidity flow induced by summer rainfall events on water supply, aquatic ecosystems, and socioeconomics are significant and major concerns in most of reservoirs operations. As a decision support tool, the real-time turbidity flow monitoring and modeling system RTMMS is under development using a laterally integrated two-dimensional (2D) hydrodynamic and water quality model. The objectives of this paper is to present the preliminary field observation results on the characteristics of rainfall-induced turbidity flows and their density flow regimes, and the model performance in replicating the fate and transport of turbidity plume in a reservoir. The rainfall-induced turbidity flows caused significant drop of river water temperature by 5 to $10^{\circ}C$ and resulted in density differences of 1.2 to $2.6kg/m^3$ between inflow water and ambient reservoir water, which consequently led development of density flows such as plunge flow and interflow in the reservoir. The 2D model was set up for the reservoir. and applied to simulate the temperature stratification, density flow regimes, and temporal and spatial turbidity distributions during flood season of 2004 After intensive refinements on grid resolutions , the model showed efficient and satisfactory performance in simulating the observed reservoir thermal stratification and turbidity profiles that all are essentially required to enhance the performance of RTMMS.

• Korean Journal of Soil Science and Fertilizer
• /
• v.44 no.1
• /
• pp.78-83
• /
• 2011

Phosphorus (P) which is required by all living plants and animals is an important input for economic crop and livestock production systems. Phosphorus containing compounds are essential for photosynthesis in plants, for energy transformations and for the activity of some hormones in both plants and animals. Loss of soil P to water can occur in particulate forms of P with eroded surface soil and in soluble forms in runoff, soil interflow, and deep leaching. The excessive losses of P from agricultural systems can degrade water quality of surface waters, resulting in accelerating eutrophication. Thus, P is often the limiting element and its control is of prime importance in reducing the accelerated eutrophication of surface waters. However, reserves of phosphate begin to run out, the impacts are likely be immense in terms of rising food prices, growing food insecurity. This paper reviews underappreciated resource as a key component of fertilizers and one of controversial pollutant in terms agronomy and environment.

• Journal of Environmental Science International
• /
• v.23 no.7
• /
• pp.1223-1232
• /
• 2014

Density currents have been easily observed in environmental flows, for instance turbidity currents and pollutant plumes in the oceans and rivers. In this study, we explored the propagation dynamics of density currents using the FLOW-3D computational fluid dynamics code. The renormalization group (RNG) $k-{\varepsilon}$ scheme, a turbulence numerical technique, is employed in a Reynold-averaged Navier-Stokes framework (RANS). The numerical simulations focused on two different types of intrusive density flows: (1) propagating into a two-layer ambient fluid; (2) propagating into a linearly stratified fluid. In the study of intrusive density flows into a two-layer ambient fluid, intrusive speeds were compared with laboratory experiments and analytical solutions. The numerical model shows good quantitative agreement for predicting propagation speed of the density currents. We also numerically reproduced the effect of the ratio of current depth to the overall depth of fluid. The numerical model provided excellent agreement with the analytical values. It was also clearly demonstrated that RNG $k-{\varepsilon}$ scheme within RANS framework is able to accurately simulate the dynamics of density currents. Simulations intruding into a continuously stratified fluid with the various buoyancy frequencies are carried out. These simulations demonstrate that three different propagation patterns can be developed according to the value of $h_n/H$ : (1) underflows developed with $h_n/H=0$ ; (2) overflows developed when $h_n/H=1$ ; (3) intrusive interflow occurred with the condition of 0 < $h_n/H$ < 1.

• Magazine of the Korean Society of Agricultural Engineers
• /
• v.35 no.1
• /
• pp.40-49
• /
• 1993

The Objectives of this paper were to develop a modified tank model that is capable of simulating daily streamflow from a small watershed using daily watershed evapotranspiration and to test the applicability of the model to different watersheds. Tank model was restructured to consist of three series of tanks, each of which may mathematically reflect watershed runoff mechanisms from different components of surface runoff, interflow, and baseflow. And pan evaporation was correlated to potential evapotranspiration estimated from a combination method, and was multiplied by monthly crop and landuse coefficients, and watershed storage coefficient to estimate the watershed evapotranspiration losses. Ten watersheds were selected to calibrate model parameters that were defined using an optimization scheme, and the results were correlated with watershed parameters. Simulated daily runoff was compared to the observed ones from the tested watersheds. The simulating results were in good agreement with the observed values when optimal and calibrated parameters were used. Ungaged conditions were also applied to compare simulated values to the observed. And the results were in fair conditions for all the tested watersheds which differ considerably in their sizes, landuse types, and physiological features.

• Journal of the Korean association of regional geographers
• /
• v.14 no.1
• /
• pp.19-26
• /
• 2008

A validation study has been performed using the Soil and Water Assessment Tool(SWAT) model with data collected for the Neponset River watershed, which includes roughly 130 square miles of land located southwest of Boston. All of this land drains into the Neponset River, and ultimately into Boston Harbor. This paper presents the methodology of a SWAT model. The calculated contribution of the baseflow to the streamflow is far too high whereas the interflow is strongly underestimated. Alternatively, the modified and calibrated model yields far better results for the catchment. The modification allows hydrological processes to be modeled while not restraining the applicability of the model to catchments with other characteristics. For this study, the SWAT 2005 model is used with ArcGIS 9.1 as an interlace, and sensitivity analysis is performed to provide rough estimated values before adjusting sensitive input parameters during calibration period.

• Journal of Korean Society on Water Environment
• /
• v.29 no.1
• /
• pp.97-106
• /
• 2013

The temporal and spatial variations of water quality in a stratified reservoir are fully dependent on the characteristics of inflow loading from its watershed and the transport regimes of pollutants after entering the reservoir. Because of the meteorological and hydrological conditions in Korea, the pollutants loading to reservoirs are mostly occur during rainfall events. Therefore it is important to understand the characteristics of pollutants loading from upstream rivers and their spatial propagation through the stratified reservoir during the rainfall events. The objectives of this study were to characterize the water quality variations in upstream rivers of Imha Reservoir during a rainfall event, and the transport and spatial variations of pollutants in the reservoir through extensive field monitoring and laboratory analysis. The results showed that the event mean concentration (EMC) of SS, BOD, $COD_{Mn}$, T-N, T-P, $PO_4-P$ are 8.6 ~ 362.1, 2.5 ~ 5.1, 1.5 ~ 5.1, 1.1 ~ 1.9, 8.3 ~ 57.1, 5.6 ~ 25.7 times greater than the mean concentrations of these parameters during non-rainfall period. The turbidity and SS data showed good linear correlations, but the relationships between flow and SS showed large variations because of hysteresis effect during rising and falling periods of the flood. The ratio of POC to TOC were 12.6 ~ 14.7% during the non-rainfall periods, but increased up to 28.2 ~ 41.7% during the flood event. The turbid flood flow formed underflow and interflow after entering the reservoir, and delivered a great amount of non-point pollutants such as labile and refractory organic matters and nutrients to the metalimnion layer of reservoir, which is just above the thermocline. Spatially, the lateral variations of most water quality parameters were marginal but the vertical variations were significant.

• Journal of the Mineralogical Society of Korea
• /
• v.19 no.3 s.49
• /
• pp.139-151
• /
• 2006

Base metal sulfides occur in the Huronian sedimentary rocks that cover the Archean volcanic rocks in the Cobalt area, Ontario, Canada. They are mostly concentrated in the basal conglomerate which was formed in the pre-Huronian basin structure. Sulfide occurrence can be grouped as massive sulfide clasts in the basal and Coleman conglomerate, disseminated sulfides throughout the sediments, and disseminated sulfides near Ag-Co-Ni-As carbonate veins. Detrital mechanism can explain features such as angularity of sulfide fragments and graded bedding of dissemnated sulfides. Sulfides concentrated near carbonate veins are probably of hydrothermal origin. Nearby strata-bound type massive sulfide ore deposits and mineralized interflow units are the most probable sources for syngenetic sulfides. This is supported by the angularity of sulfide fragments, presence of massive sulfide boulders which are identical in mineralogy and texture to the strata-bound type sulfide deposits in the Archean basement, and a similar composition of sphalerite in the Archean volcanic rocks and Huronian sedimentary rocks. Some sulfide grains, especially in sandstones and argillites, were undergone recrystallization during the intrusion of the Nipissing diabase.

• Korean Journal of Ecology and Environment
• /
• v.41 no.2
• /
• pp.247-263
• /
• 2008

A two-dimensional (2D) reservoir hydrodynamics and water quality model, CE-QUAL-W2, is employed to simulate the hydrothermal behavior and density current regime in Andong Reservoir. Observed data used for model forcing and calibration includes: surface water level, water temperature, dissolved oxygen and suspended solids concentration. The model was calibrated to the year of 2003 and verified with continuous run from 2000 till 2004. Without major adjustments, the model accurately simulated surface water levels including the events of large storm. Deep-water reservoirs, like Andong Reservoir, located in the Asian Monsoon region begin to stratify in summer and overturn in fall. This mixing pattern as well as the descending thermocline, onset and duration of stratification and timing of turnover phenomenon were well reproduced by the Andong Model. The temperature field and distinct thermocline are simulated to within $2^{\circ}C$ of observed data. The model performed well in simulating not only the dissolved oxygen profiles but also the metalimnetic dissolved minima phenomenon, a common1y occurring phenomenon in deep reservoirs of temperate regions. The Root Mean Square Error (RMSE) values of model calibration for surface water elevation, temperature and dissolved oxygen were 0.0095 m, $1.82^{\circ}C$, and $1.13\;mg\;L^{-1}$, respectively. The turbid storm runoff, during the summer monsoon, formed an intermediate layer of about 15 m thickness, moved along the metalimnion until being finally discharged from the dam. This mode of transport of density current, a common characteristic of various other large reservoirs in the Asian summer monsoon region, was well tracked by the model.

• Journal of Microbiology and Biotechnology
• /
• v.23 no.7
• /
• pp.993-1003
• /
• 2013

Methanotrophs are the most important sink of $CH_4$, which is a more highly potent greenhouse gas than $CO_2$. Methanotrophic abundance and community diversity in cover soils from two typical semi-aerobic landfills (SALs) in China were detected using real-time polymerase chain reaction (real-time-PCR) and denaturing gradient gel electrophoresis (DGGE) based on 16S rRNA genes, respectively. Real time-PCR showed that Type I methanotrophs ranged from $1.07{\times}10^6$ to $2.34{\times}10^7$ copies/g soil and that of Type II methanotrophs from $1.51{\times}10^7$ to $1.83{\times}10^8$ copies/g soil. The ratio of Type II to Type I methanotrophic copy numbers ranged from 5.61 to 21.89, indicating that Type II methanotrophs dominated in SAL. DGGE revealed that Type I methanotrophs responded more sensitively to the environment, changing as the community structure varied with different soil types and locations. Methylobacter, Methylosarcina, and Methylomicrobium for Type I, and Methylocystis for Type II were most prevalent in the SAL cover layer. Abundant interflow $O_2$ with high $CH_4$ concentration in SALs is the reason for the higher population density of methanotrophs and the higher enrichment of Type II methanotrophs compared with anaerobic landfills and other ecosystems, which proved a conclusion that increasing the oxygen supply in a landfill cover layer would greatly improve $CH_4$ mitigation.

• Journal of Korea Water Resources Association
• /
• v.47 no.1
• /
• pp.1-10
• /
• 2014

This study aimed to analyze water cycle at Taehwa river, Dongcheon, Hoiya river and Cheongryang cheon in Ulsan city using CAT model developed by Korea Institute of construction technology. To apply CAT model, we separated Teahwa river into 25, Dongcheon into 11, Hoiya river into 17 and Cheongryangcheon into 5 subbasins and discriminated between contribution runoff basins and source basins. The results of water cycle analysis performed using rainfall datas measured from 1975 and 2008 and hydrologic datas of change of land use etc. were that surface runoff increase and interflow decrease, caused by the increase of impervious area. The increases of surface runoff at the basin of Taehwa river and Dongcheon which is a tributary of Taehwa river were small and similar to each other respectively as 1.7% and 2.4%, and increased high rate of 3.2% and 7.7% in Hoiya river and Cheongryangcheon including subbasins which are having high rate of urbanization.