• Water Engineering Research
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• v.1 no.3
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• pp.171-185
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• 2000

A mathematical model to adequately predict complex mixing characteristics of sorptive polluants in natural streams with pools-and-riffes has been developed. In this model, sorption of pollutants onto the bed sediment as well as mass storage and exchange in the storage zones were incorporated into one-dimensional mass balance equatins. The geometric and hydraulic characteristics of the pool-riffle sequences were properly conceptualized. Simulations with parameters of pool-and-riffle streams better fit the measured data in overall shape and peak concentration than simulations with parameters for uniform channels. The analyses on the characteristics of the storage zone model parameters reveal that a linear relationship between the logrithm of the storage zone volume ratio and a function of the friction factor exists. A linear relatiohship might also be tenatively assumed between the logarithm of the dimensionless mass exchange coefficient and the logarithm of the aspect ratio of the storage zone if some of the high values of the dimensionless mass exchange coefficient collected on the successive bed forms are excluded.

• Journal of Wetlands Research
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• v.5 no.1
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• pp.67-78
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• 2003

The unsteady 2D convection and diffusion equation is solved numerically for the real-time simulation of suspended load propagation. The streamlined upwind scheme efficiently reduces numerical oscillations due to the high Peclet number in the convection dominant flow. By using the mixed boundary condition to express the external source terms or externally induced suspended load as a function of time in the algorithm, the model is capable of handling not only continuous load cases but also non-continuous suspended load influx. The suspended load transport modelwas verified using a case study for which an analytical exact solution is available and was applied to the real-time simulation of a suspended load influx case on the Mississippi River. The model algorithm can provide a framework upon which water quality as well as contaminant transport models can be built.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2001.05a
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• pp.154-159
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• 2001

Nakdong estuary is located at south-eastern coast of the Korea. A lot of sediment from upper river was deposited at this area. It has caused many problems such as changes in topography and tidal current. In this paper, field observation data on tidal currents and sediments were investigated as well as historical topographic changes by dredging and reclamation of the foreshore. Then, the numerical model considered the settling velocity of the suspended solids according to the particle size was applied to examine the characteristic of deposition. The results are as follows : 1. Changes of characteristics of deposition were caused by topographic changes of Nakdong estuary 2. Characteristics of deposition were influenced by river plume and tidal currents. 3. Numerical model which considers settling velocity reappeared distribution of deposition by particle-size. 4. Used model is only resonable for discussion in the quality, so, it is strongly suggested that the new model development is needed including the quatitative deposition processes.

• 한국방재학회:학술대회논문집
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• 2008.02a
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• pp.783-786
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• 2008

The main goal of this study is to understand the effects of direct-runoff of chemistry and organic fertilizers which are adsorbing to sediment from farmland and non-point source discharge characteristics which are discharged to stream with soil erosion when rainfalls. pollutographs of TSS, BOD, COD, TN, and TP were measured for 10 rainfall events at watershed. EMC (Event Mean Concentration) were calculated for each rainfall event using quality and quantity measured. The result shows that the EMC ranges of 95% confidence intervals are 50.5-203 mg/L for TSS, 0.8-14.2 mg/L for $BOD_5$, 4.2-20.7 mg/L for $COD_{Mn}$, 0.2-0.5 mg/L for TP, 2.4-4.5 mg/L for TN, 1.36-3.04 mg/L for NO3--N, 0.13-0.42 mg/L for NH4+-N and 0.82-1.77 mg/L for TKN.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.150-150
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• 2021

Soil erosion due to climate change is one of the global environmental issues. Especially, Korea is vulnerable to soil erosion as the frequency of extreme rainfall events and rainfall intensity are increasing. Soil erosion causes various problems such as reduced farmlands, deterioration of water quality in rivers, etc. To these severe problems, understanding the process of soil erosion is the first process. Then, it is necessary to quantify and analyze soil ersoion using an erosion model. Soil erosion models are divided into empirical, conceptual, and physics-based models according to the structures and characteristics of models. This study used GSSHA (Gridded Surface Subsurface Hydrologic Analysis), the physics-based erosion model, running on WMS (Watershed Modeling System) to analyze soil erosion vulnerability of the CheonCheon watershed. In addition, we compared the six sediment transport capacity formulas provided in the model and evaluated the equations fir on this study site. Therefore, this result can be as a primary tool for soil conservation management.

• Journal of Korean Society of Environmental Engineers
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• v.39 no.10
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• pp.581-590
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• 2017

For effective improvement of water quality in Seokmun reservoir, this study implemented various analyses including the tributary water quality and flowrate monitoring, contamination of sediment, investigation of pollution source, selection of priority management target tributary by stream grouping method. The COD concentration of the majority of tributaries in Seokmun reservoir watershed was relatively higher than BOD concentration. The concentration of water pollutants regardless of water quality parameters in Yeokcheon, Dangjincheon, Sigokcheon, Baekseokcheon, small stream in Jinkwanri and Janghangri were higher than the other tributaries. The pollution sources in the Seokmun reservoir watershed were mostly distributed in the population, livestock, and industry. The pollutants, which located in Yeokcheon, Dangjincheon, Baekseokcheon, and small stream in Janghangri selected as priority management target tributary, should be preferentially reduced for improving the water quality in Seokmun reservoir. As the evaluation results of water quality in Seokmun reservoir for the effect of water quality improvement according to various scenarios using water quality model, it was found that the water quality in Seokmun reservoir due to the construction of a wastewater treatment plant for management of pollutants in the watershed would be satisfied the class V of water environment standard in reservoir.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.17 no.5
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• pp.29-41
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• 2014

Ecosystem services provide various benefits to human beings, but are considered to be free of cost. To protect ecosystems in an economically sustainable way, several developing countries have adopted a policy known as the Payment for Ecosystem Services (PES) that compensates upstream services with monetary incentives collected from service users. Vietnam is one of the countries that have enacted a nationwide PES policy. However, the policy in Vietnam requires further development in order to evaluate the spatial priority zones based on the quantification of ecosystem services. To obtain a recent and high-quality land cover map, we first classified the land cover in the Da River basin, in northern Vietnam, using Landsat dataset. We then applied a water balance theory and an USLE equation to assess hydrological ecosystem services concerning water supply and sediment retention. Following the assessment, we identified the priority areas for hydrological ecosystem services exclusively for forest environments. We found that the quantity and distribution of services from forests varied, due to the topography, climate, and land cover. According to a quantile distribution, Mt. Phu Luong, Mt. Fansipan, and Hoang Lien National Park were evaluated as high service areas in terms of both water yield and sediment retention. As a result, this assessment method can help construct spatial priority zones concerning ecosystem service distribution, and can also contribute to benefit sharing by indicating which forest and landowners require compensation.

• Journal of the Korean Society of Marine Environment & Safety
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• v.19 no.2
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• pp.101-110
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• 2013

In order to classify the trophic state and environmental quality of marine coastal system, an approach using the characteristics and biochemical composition in the sediments can be available. This research, including 25 coastal bay, belong to 131 stations, was carried out along the south coasts of Korea in February 2007. Type of sediment, total ogranic carbon, total nitrogen, phytopigments and biochemical composition(proteins, lipids, carbohydrates) were analyzed. Result from Multi-dimensional Scaling(MDS) ordination indicates that four group can be identified. The result of ANOVA with tukey test shows that the concentrations of proteins, carbohydrates and biopolymeric carbon were significantly different to four groups. We propose the trophic state classification for these groups using the biochemical composition of sediment organic matter. I group(Masan, Jinhae, Haengam) has been defined as hypertrophic state, II group(Tongyeong, Goseong；Jaran, Geoje et al.), as eutrophic; III group(Gamak, Deungnyang, Yeoja et al.), as mesotrophic and IV group(Sinan, Jindo, Muan), as oligotrophic. On the basis of results reported in this study, the biochemical composition of sediment organic matter could be considered an useful and sensitive tool for the classification of the trophic state of marine coastal systems.

• Journal of Wetlands Research
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• v.13 no.3
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• pp.443-453
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• 2011

This research aims at suggesting the mitigation measures of decreasing pollution by analyzing land cover characteristics according to subwatershed, and non-pollutant load characteristics occurring in each subwatershed. Mushim-cheon is selected as a research area, and HyGIS-SWAT is used as a water quality model. This research analyzed outflow load characteristics by classifying land cover, which has over 50% classified items, into a city area, a farmland area and a forest area. The result shows that the yearly occurrence load quantity represents a farmland area, a forest area and a city area in order. In subwatershed-2, occurrence load quantity is analyzed by setting up a buffer zone in the center of stream, and by changing a farmland area into a natural grass land. Therefore, a farmland area in a subwatershed changes 36.6% into 27.9% and 15.3% comparing to previous land cover change. In the analysis of sediment loads occurrence quantity and nutritive salt load occurrence quantity in subwatershed-2, sediment loads occurrence quantity decreases 52% to about 47%, and nutritive salt load decreases 49% and 34% in compare with previous change. Hereafter, this research will set up the mitigation measures scenario, and find out which is more effective for the mitigation measures.

• Journal of Korean Society on Water Environment
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• v.28 no.2
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• pp.255-268
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• 2012

Nonpoint source pollution has become a concern for water quality in the Han River system, especially during the high runoff events during the monsoon season. The patterns in nonpoint source runoff the relationships with land use, rainfall intensity, and stream nutrients concentrations were surveyed in 19 streams in the Han River watershed. The results show that the magnitude of NPS inputs of nutrients and sediment in the Han River watershed are of a serious concern. In the South Han River watershed, event mean concentrations (EMC) for biochemical oxygen demand (BOD), suspended sediment (SS), dissolved organic carbon (DOC), dissolved total phosphorus (DTP), total nitrogen (TN) Nitrate ($NO_3$-N) and total phosphorus (TP) were $1.94mg{\cdot}L^{-1},\;251mg{\cdot}L^{-1},\;2.75mg{\cdot}L^{-1},\;0.076mg{\cdot}L^{-1},\;2.82mg{\cdot}L^{-1},\;2.40mg{\cdot}L^{-1}$ and $0.232mg{\cdot}L^{-1}$, respectively. In the North Han River watershed, EMCs for BOD, SS, DOC, DTP, TN, $NO_3$-N and TP were $1.34mg{\cdot}L^{-1},\;172mg{\cdot}L^{-1},\;2.63mg{\cdot}L^{-1},\;0.032mg{\cdot}L^{-1},\;1.97mg{\cdot}L^{-1},\;1.55mg{\cdot}L^{-1}$ and $0.148mg{\cdot}L^{-1}$, respectively. The specific export coefficients of nutrient and sediments were much higher than those of other reports. Our study also found that the proportion of agricultural field area was significantly correlated with the EMCs for nutrients. Therefore, efforts to reduce NPS loading must focus on agricultural practices in the watershed. The relationships between land use and nutrient and sediment export found in this study can be used to derive estimates of runoff coefficients for agricultural field and as input data for modeling works and to develop total maximum daily load and best management practices in the Han River watershed.