• Korean Journal of Ecology and Environment
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• v.36 no.1 s.102
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• pp.57-65
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• 2003

The algal growth potential test (AGPT) bioassay were conducted to assess the water quality and fertility in the Chinyang Reservoir and the lower part of the Nam River from August 2000 to July 2001, The AGPT value of the Chinyang Reservoir ranged from 0 to 23.4 mg dw $1^{-1}$, while 79% of the algae cultivation have not grown. The AGPT value was in proportion to phosphorus concentration of the water, and it was less when chlorophyll-a was high. This value was higher in the middle and lower layers than in the upper layer, and in the inflow part where the water is shallower than in the lacustrine. The AGPT value has increased in the whole reservoir in August${\sim}$September when the water volume is high. In contrast, the AGPT value in the Nam River varied greatly compared to that of the reservoir, and ranged from 0 to 252.0 mg dw $1^{-1}$ and 65% of the algae cultivation have grown. The value was less than 10 mg dw $1^{-1}$ in the upstream, over the point where the treated wastewater discharged. It was 57 mg dw $1^{-1}$ on the average in the downstream, except in March and July when the discharged water influenced greatly, exceeding the hypertrophic condition. The result of AGPT shows the differences in the time and space on the reservoir and the streams. The AGPT value has increased in July${\sim}$September, and in December in the inflow part of the reservoir; in March and August${\sim}$December in the lower part; and in January, May, and November in the streams. AGPT is useful not only in defining the influence of the limiting nutrients on the algal growth, but also in evaluating the nutrients fertility in the inland water.

• Korean Journal of Ecology and Environment
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• v.41 no.3
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• pp.348-359
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• 2008

The objectives of the study were to elucidate functional modifications in relation to hydrological, physico-chemical and ecological aspects in Daechung Reservoir by the upper dam constructions of Youngdam Reservoir and analyze temporal and spatial dynamic patterns using trophic parameters of TN, TP, chlorophyll (CHL), and Secchi depth (SD). Hydrological data such as inflow, precipitation, and water levels before (BDC, 1995$\sim$2000) and after (ADC, 2001$\sim$2006) the dam construction showed that precipitation had greater correlations with inflow volume in the BDC (r=0.964, p=0.002) than in the ADC (r=0.857, p=0.029). This outcome indicates that the upper dam construction influenced the inflow and water level of Daechung Reservoir. One of the greatest changes after the dam construction was decreases of nutrient contents (TN, TP) and increases of algal biomass (as CHL) as the water residence time increases. Values of CHL had greater relations with TP in the ADC (r=0.412, p<0.001) than the BDC (r=0.249, p<0.001), indicating that CHL had greater response at a given phosphorus in the ADC. Thus, algal yield at a given TP (CHL : TP ratios) increased in the ADC, resulting in a greater CHL-TP relations. Long-term interannual TP, TN, SD, and CHL showed greater variations in the riverine zone (RZ) than any other transition (TZ) and lacustrine zones (LZ). This phenomenon was mainly attributed to rapid hydrological response in the riverine zone (RZ) to flow reductions (short water residence time) from the upper dam, resulting in ambient contents of nutrients and light regime along with functional relations of CHL-TP.

• Geophysics and Geophysical Exploration
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• v.11 no.3
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• pp.242-249
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• 2008

Recently, AVO analysis has been widely used in oil exploration with seismic subsurface section as a direct indicator of the existence of the gas. In the case of the deep reservoirs like the gas reservoirs in the East-sea, it is often difficult to observe AVO responses in CMP gathers even though the bright spots are shown in the stacked section. Because the reservoir becomes more consolidated as its depth deepens, P-wave velocity does not decrease significantly when the pore fluid is replaced by the gas. Thus the difference in Poisson's ratio, which is a key factor for AVO response, between the reservoir and the layer above it does not increase significantly. In this study, we analyzed the effects of Poisson's ratio difference on AVO response with a variety of Poisson's ratios for the upper and lower layers. The results show that, as the difference in Poisson's ratio between the upper and lower layers decreases, the change in the reflection amplitude with incidence angle decreases and AVO responses become insignificant. To consider the limitation of AVO responses shown in the gas reservoir in East-sea, the velocity model was made by simulation Gorae V structure with seismic data and well logs. The results of comparing AVO responses observed from the synthetic data with theoretical AVO responses calculated by using material properties show that the amount of the change in reflection amplitude with increasing incident angle is very small when the difference in Poisson's ratio between the upper and lower layers is small. In addition, the characteristics of AVO responses were concealed by noise or amplitude distortion arisen during preprocessing. To overcome such limitations of AVO analysis of the data from deep reservoirs, we need to acquire precisely reflection amplltudes In data acquisition stage and use processing tools which preserve reflection amplitude in data processing stage.

• Korean Journal of Environmental Biology
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• v.30 no.1
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• pp.15-25
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• 2012

From April to November 2009, we performed field investigation to survey the characteristics of fish fauna and fish community structure inhabited in Yongdam reservoir in the upper Geumgang, which is changed into flat-water zone from flow-water zone by blocking the continuity by the gigantic submerged weir built in the upstream of Geumgang. 15 species belonging to 8 families were collected from natural habitat (St. 1) where its natural characteristics is well preserved, and 11 species were korean endemic fish species. 24 species belonging to 10 families were collected at the down region of Yongdam dam (St. 3), which might be affected by the change of water environment due to the dam, and 11 species were korean endemic fish species. On the other hand, 20 species belonging to 7 families were collected inside Yongdam reservoir (St. 2) which is changed into flat-water zone from flow-water zone by the dam reservoir, and 6 species were korean endemic fish species. In the dam reservoir, due to Yongdam dam built in the upper Geumgang, the original flow-water zone fish such as $Acheilognathus$ $koreensis$, $Pseudopungtungia$ $nigra$, $Coreoleuciscus$ $splendidus$, and $Gobiobotia$ $macrocephala$ were disappeared, and instead, the kinds of fish habitating in the flat-water zone tend to increase rapidly, such as $Carassius$ $auratus$, $Opsarichthys$ $uncirostris$ $amurensis$, $Hemiculter$ $eigenmanni$, $Zacco$ $platypus$, and $Lepomis$ $macrochirus$. Relative abundance of the insective fish was 66.7% at St. 1, 40.0% at St. 2, and 54.2% at St. 3. In order to preserve endemic fish species and aquatic ecosystem, it is desirable to minimize the artificial installation in the upper river, such as a large scale dam which can affect the habitat and if inevitable, it is required to prepare preservation measures when building facilities.

• Journal of the Korean GEO-environmental Society
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• v.7 no.4
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• pp.35-41
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• 2006

This paper analyzed elution and ingredients of soil components which consist of soil and rocks in 6 regions in Yeongyang and Cheongsong to identify substantial matters that cause muddy water in Imha reservoir. We identified that more than 80% of major ingredients in collected soil and rocks are vermiculite(V), illite(I), kaolinite(Ka), quartz(Q), feldspar(F). Sodium and calcium are eluted in large quantities from soil of Sanseong and Cheongki. When calcium is in contact with water, much ions are eluted rapidly. We confirmed these ions are alkali minerals rising pH. We consider clay components distributed in Yeongyang as major cause of muddy water and rising pH of Imha reservoir because its ingredient calcite easily is dissolved in rainwater and splits other mineral particles into ${\mu}m$ sized particles.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.10 no.4
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• pp.159-171
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• 1990

The purpose of this study was development and application of a multiple box model for long term prediction and control of water quality in estuary reservoir. The model was composed of one main model and two sub models for hydrology and water quality. Water quality constituents for modeling were temperature, chlorophyll-a, BOD, DO, N, and P. The model had been applied to Asan reservoir, and the reservoir had been devided into three boxes-two boxes for a upper layer and one box for a lower layer-to represent stratification. The model appeared satisfactory in representing long term trend of water quality variations by comparing measured and simulated results. According to the application of the model to study alternatives for water quality improvement to deal with increase in future pollution load, use of non-phosphorous detergent for chlorophyll-a, advanced sewage treatment for BOD and T-N, reduction of livestock waste for T-P were evaluated as more effective ones than any others, respectively.

• Journal of the Korean Society of Hazard Mitigation
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• v.5 no.2 s.17
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• pp.37-44
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• 2005

It reflects well feature of slope that is characteristic of urban river basin of Busan local. In this study, process various hydrological data and basin details data which is collected through basin basis data, hydrological monitoring system(EMS-DEU) and automatic water level equipment(AWS-DEU) for urban flood disaster prevention and use as basin input data of ILLUDAS, SWMM and HEC-HMS in order to examine outflow feature of experiment basin and then use in reservoir design of experiment basin through calibration and verification about HEC-HMS. Inserted design rainfall for 30 years that is design criteria of creek into HEC-HMS and then calculated design floods according to change aspect of the impermeable rate. Capacity of reservoir was determined on the outflow mass curve. Designed detention pond(volume $54,000m^3$) at last outlet upper stream of experiment basin, after designing reservoir. It could be confirmed that the peak flow was reduced resulting from examining outflow aspect. Designing reservoir must decrease outflow of urban areas.

• 한국지구물리탐사학회:학술대회논문집
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• 2008.10a
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• pp.47-50
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• 2008

Streamer resistivity surveys in shallow marine environments were carried out to analyze sediment characteristics at the bottom of reservoir. Because the resistivity values of reservoir water are very low and those of sediment are relatively high, apparent resistivity values increase with depth. And it is necessary to eliminate the apparent resistivity data decreased highly when the number of separation increases. According to the repeated data processing, we proposed the resistivity ratio of upper-to-lower layer is $0.6{\sim}0.8$ because the RMS error of inversion leads to the minimum in these range. As a result of the inversion for two- and three-layer model, the inversion including water depth is proved to be more effective than conventional method.

• Computers and Concrete
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• v.10 no.3
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• pp.277-294
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• 2012

The aim of the study is to determine the modal parameters of a prototype damaged arch dam by operational modal analysis (OMA) method for some damage scenarios. For this purpose, a prototype arch dam-reservoir-foundation model is constructed under laboratory conditions. Ambient vibration tests on the arch dam model are performed to identify the modal parameters such as natural frequency, mode shape and damping ratio. The tests are conducted for four test-case scenarios: an undamaged dam with empty reservoir, two different damaged dams with empty reservoirs, and a damaged dam with full reservoir. Loading simulating random impact effects is applied on the dam to crack. Cracks and fractures occurred at the middle of the upper part of the dams and distributed through the abutments. Sensitivity accelerometers are placed on the dams' crests to collect signals for measurements. Operational modal analysis software processes the signals collected from the ambient vibration tests, and enhanced frequency domain decomposition and stochastic subspace identification techniques are used to estimate modal parameters of the dams. The modal parameters are obtained to establish a basis for comparison of the results of two techniques for each damage case. Results show that approximately 35-40% difference exists between the natural frequencies obtained from Case 1 and Case 4. The natural frequencies of the dam considerably decrease with increasing cracks. However, observation shows that the filled reservoir slightly affected modal parameters of the dam after severe cracking. The mode shapes obtained are symmetrical and anti-symmetrical. Apparently, mode shapes in Case 1 represent the probable responses of arch dams more accurately. Also, damping ratio show an increase when cracking increases.

• Journal of The Geomorphological Association of Korea
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• v.26 no.4
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• pp.1-20
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• 2019

In order to establish appropriate policy to control sediment-associated problems, it is necessary to identify the physical characteristics of the reservoir sediments in particulate form in the Yeongsan River. Two time-integrated suspended sediment samplers were installed at Seungchon and Juksan weir on the upper and middle Yeongsan River in July 2012. Reservoir sediment samples were obtained at monthly intervals until October 2014. During the monitoring period, a total of 38 sediment samples were obtained and analyzed. Seasonal trends of suspended sedimentation rates and grain size distributions were examined based on variations in precipitation and discharge fluctuations. Moreover, stream flow characteristics, which has a great influence on the physical characteristics of the river sediment, was analyzed using flow duration curve for the period 2003-2019 at Naju gauging station. Sedimentation rates during summer, when heavy rainfall was concentrated due to the monsoonal front and typhoon, were very high, indicating the positive relationship between sediment concentration and discharge. Particle size analysis of the collected sediment showed that coarse silt and very fine sand-sized sediment dominated most of the Seungchon weir sediment. On the other hand, medium silt-sized sediment dominated the downstream Juksan weir except for a few summer samples. These results implied that the physical characteristics of the suspended sediment are determined not only due to flow fluctuations, but also with regard to the antecedent rainfall conditions, hillslope-channel connectivity, and the supply of materials from various contributing regions. This information about flow characteristics and temporal variations in reservoir sediment can be used for safe management of the weir and discussing the issues on the dismantling of the weirs.