• Title/Summary/Keyword: sub stream

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Quantitative Evaluation of Energy Coupling between Quasi-Periodic Substorms and High-Speed Coronal Streams (준 주기적인 서브스톰과 고속 태양풍 사이의 에너지 결합에 대한 정량적 평가)

  • Park, M.Y.;Lee, D.Y.;Kim, K.C.;Choi, C.R.;Park, K.S.
    • Journal of Astronomy and Space Sciences
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    • v.25 no.2
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    • pp.139-148
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    • 2008
  • It has been known that high-speed solar wind streams associated with coronal holes lead to quasi-periodic substorms that occur approximately every $2{\sim}4$ hours. In this paper we examined 222 repetitive substorms that occurred during high-speed stream periods in July through December in 2003 to quantitatively determine a range of energy input from the solar wind into the magnetosphere between two consecutive substorms. For this study, we have used the Akasofu ${\varepsilon}$-parameter to time-integrate it for the interval between two consecutive substorms, and have applied this method to the 222 substorms. We find that the average amount of solar wind input energy between two adjacent substorms is $1.28{\times}10^{14}J$ and about 85% out of the 222 substorms occur after an energy input of $2{\times}10^{13}{\sim}2.3{\times}10^{14}J$. Based on these results, we suggest that it is not practical to predict when a sub storm will occur after a previous one occurs purely based on the solar wind-magnetosphere energy coupling. We provide discussion on several possible factors that may affect determining substorm onset times during high-speed streams.

Water Chemistry Characteristics and Fish Fauna of Sodo Stream Watershed in Taebaeksan Provincial Park (태백산 도립공원 내 소도천 수계의 이·화학적 수질 특성 및 어류상)

  • Han, Jeong-Ho;Paek, Woon Kee
    • Korean Journal of Environment and Ecology
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    • v.30 no.1
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    • pp.71-80
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    • 2016
  • The fauna of freshwater fish and water chemistry characteristics were investigated from June, 2014 to October, 2014 at 10 sites in Taebaeksan Provincial Park. A total of 7 species under three families were collected from the survey sites and among them one endangered species - Koreocobitis naktongensis - was identified. The endemic species of Korea were 2 species: Koreocobitis naktongensis, Iksookimia koreensis. Dominant species was Rhynchocypris oxycephalus(89%) and subdominant species was Orthrias nudus(8.9%). Water quality including conductivity, turbidity, pH and total dissolved solids(TDS) varied largely depending on the sampling locations. Values of ambient conductivity and TDS were greater in the upstream than in the downstream, and seasonal variabilities were also higher in the upstream. The pH decreased towards the downstream, and especially showed a sharp decrease in S5. This phenomenon was evident due to a dilution by the influx in the acid mine drainage(AMD) of S4. Physical habit conditions, based on qualitative habitat evaluation index(QHEI) model, indicated a "Sub-optimal" condition(mean: 157.3; range: 78 ~ 194) in the Sodo stream watersheds.

Evaluation and Application of QUAL2E and QUAL2K Models in Anyang Stream (안양천에서 QUAL2E와 QUAL2K 모델의 적용 및 평가)

  • Jung, Sung-Soo;Kim, Kyung-Sub
    • Journal of Korean Society of Environmental Engineers
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    • v.30 no.5
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    • pp.544-551
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    • 2008
  • QUAL2K enhanced QUAL2E and applied in real fields efficiently incorporates denitrification process, sediment-water interaction process, bottom algae and detritus. Also, the CBOD of QUAL2K is divided into two real parts, one is slow CBOD(sCBOD) and another is fast CBOD(fCBOD). The simulation results of QUAL2E and QUAL2K models in Anyang Stream were compared and analyzed in water quality constituents of DO, BOD, Org-N, NH$_3$-N, NO$_3$-N, Org-P, Dis-P and Chl-a respectively. The similar results were shown in Org-N, NH$_3$-N, Org-P and Chl-a both QUAL2K and QUAL2E models. But the different results were revealed in DO, BOD, Dis-P and NO$_3$-N by the influence of new incorporating processes. DO was shown relatively low values in the effect of bottom algae. BOD which is influenced by particulate organic matter was revealed high values. NO$_3$-N was closed to the real values by the two processes of denitrification and sediment-water interaction. To evaluate the running results of QUAL2K and QUAL2E models, a simple statistical analysis was conducted. According to the statistical analysis, QUAL2K represented less relative error and coefficient of variation than QUAL2E in almost all of constituents. It was found that QUAL2K, which simulates the water quality more realistically, can be applied to control and manage the water problems of river or river-run reservoir effectively.

Influence on the Land Use Factors Affecting the Water Quality of Iwonchon Basin (토지이용이 이원천 유역의 하천수질에 미치는 영향)

  • 이호준;방제용;김용옥
    • The Korean Journal of Ecology
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    • v.22 no.5
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    • pp.235-240
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    • 1999
  • Characterization of water quality was performed from March 1993 to March 1998, on the purpose of clarifying the relationships between water quality and land use types. The study sites were two reservoir basins; Kaesim and Jangchan in Iwon-myon, Okchon-gun, Chungcho'ngbukdo Province. The two basins were characterized by cultivated area (Kaesim reservoir) and mountain area (Jangchan reservoir), and divided into eleven small basins, where dynamics of pollutants, and the relationship between water quality and land use types were investigated. BOD, SS and TKN became lower and lower from up-stream to down-stream, except for the small basin G where self-purification limit was exceeded. And water quality of Jangchan reservoir basin was worse because of fish nursery. Area below altitude 200m occupied 56% in Kaesim and 44% in Jangchan reservoir basins. Especially total phosphorous (Y/sub T-P/=0.2023X+0.0991, r=0.54) and total nitrogen increased in small basins where the proportion of cultivated and residential area was higher. The analysis of influences of pollutant discharge on water quality showed that pollution charge was very high in cultivated areas. The concentrations of pollutants were attenuated flowing into watersheds through physical, chemical, biochemical, and biological processes. The pollution level of mountain area was lower than that of cultivated areas.

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Temporal and Spatial Analysis of Flowrate and Water Quality of Major Tributaries for Implementation of TMDL in Sapgyo-reservoir Watershed at Chungcheongnam-do (충청남도 삽교호수계 수질오염총량관리제 시행을 위한 주요하천 유량 및 수질의 시.공간적 특성 분석)

  • Park, Sang-Hyun;Moon, Eun-Ho;Cho, Byung-Wook;Choi, Jeong-Ho;Jeong, Woo-Hyeok;Kim, Hong-Su;Yi, Sang-Jin;Kim, Young-Il
    • Journal of Korean Society on Water Environment
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    • v.29 no.1
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    • pp.107-113
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    • 2013
  • The major tributaries in Sapgyo-reservoir watershed at Chungcheongnam-do were monitored for flowrate and water quality in order to analyze the characteristics of watershed and to prepare for implementation of total maximum daily load (TMDL). According to the analytical results of flowrate and water quality monitoring data of sixteen tributaries, the tributaries with the value of flowrate over $0.5m^3/s$ were 62.5% among the monitored tributaries and the value of flowrate in the Cheonancheon, Namwoncheon, Shinyangcheon except Gokgyocheon, Muhancheon, Sapgyocheon was relatively greater than the other tributaries. However, 37.5% of the tributaries were exceeded the water quality standards of Sapgyocheon sub-basin ($BOD_5$ 5 mg/L and/or below) and the concentration of water pollutants regardless of water quality parameters in Cheonancheon, Maegokcheon, Oncheoncheon including Gokgyocheon located in Gokgyocheon catchment were relatively higher than the other tributaries. The tributaries for improving the water quality, according to stream grouping method based on the results of flowrate and water quality monitoring data, were selected. In the Sapgyo-reservoir watershed, the tributaries for improving water quality, which has a large flowrate and a high concentration of water pollutants, were selected at Cheonancheon, Gokgyocheon, Maegokcheon, Namwoncheon, Oncheoncheon. The various water quality improving plans for those tributaries, in accordance with the reduction of point source pollution by population and livestock, should be established and implemented.

Assessment of sediment and total phosphorous loads using SWAT in Oenam watershed, Hwasun, Jeollanam-do (SWAT 모델을 이용한 외남천 유역의 토사 및 총인 유출량 분석)

  • Lee, Taesoo
    • Journal of the Korean association of regional geographers
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    • v.22 no.1
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    • pp.240-250
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    • 2016
  • Monitoring for water quantity and quality was conducted in this study for 2 years (2012~2013) in Oenam Stream which is a tributary of Seomjin River and upstream of Juam Lake. Suspended solid and total phosphorous(TP) were monitored and analyzed, then water quantity and quality as well as their relation with landuses were identified based on the previous study. Flow showed the similar pattern with precipitation but some discrepancies existed due to the distance between weather station(Gwangju) and study area. Watershed was modeled based on observed data using SWAT(Soil and Water Assessment Tool). Model calibration was conducted using data obtained in 2012 and validation was conducted using data in 2013. The coefficient of determination ($R^2$) between observed and modeled showed 0.6644 and 0.5176 for flow and TP, respectively for model calibration period. For validation period, $R^2$ was 0.7529 for flow and 0.7057 for TP, which were higher than calibration period. Hot spots were determined for watershed management by analyzing the amount of sediment and TP outcome from each sub-watershed. TP loading by landuse determined that cropland, of which the area takes only 5% from entire watershed, generated 53.6% of TP and residential and cowshed was responsible for 23.5% of TP loading.

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Analysis of Groundwater Use in Kap-cheon Basin (갑천 유역의 지하수 이용 특성 분석)

  • Hong, Sung-Hun;Kim, Jeong-Kon
    • Journal of Korea Water Resources Association
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    • v.41 no.5
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    • pp.463-471
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    • 2008
  • The purpose of this study is to analyze the features of groundwater use to utilize as basic information for water-cycle analysis system development and effective groundwater management in the Kap-cheon basin. The cumulative relationship between groundwater use and the number of wells was analyzed to estimate the representative total groundwater use and the number of wells for the Kap-cheon basin. Then, the spatial distribution of groundwater use in the basin were figured out using the detailed information on groundwater use in each well. Finally, the reasonability of groundwater resources management in Kap-cheon basin was evaluated by comparing groundwater recharge and groundwater use in sub-basins and major stream basins. The results of the analysis showed about 25% of the total wells could represent 90% of groundwater use ($37,923,516\;m^3$/year) in the Kap-cheon basin. A detailed analysis on the groundwater uses in the vicinity of down-town areas of Daejeon metropolitan city showed high groundwater uses ($1.4{\sim}11.1$ times) compared to the groundwater recharge previously estimated using the rainfall-runoff model. The ratio of groundwater use and groundwater recharge for the major river basins in Kap-cheon basin ranged from 1.9 to 2.3 indicating that more sustainable groundwater management should be exercised. The results of this study can be used as basic information in evaluating the change of groundwater flow, stream flow and water-cycle for various groundwater uses in the Kap-cheon basin.

Future Inundation Risk Evaluation of Farmland in the Moohan Stream Watershed Based on CMIP5 and CMIP6 GCMs (CMIP5 및 CMIP6 GCM 기반 무한천 유역 농경지 미래 침수 위험도 분석)

  • Jun, Sang Min;Hwang, Soonho;Kim, Jihye;Kwak, Jihye;Kim, Kyeung;Lee, Hyun Ji;Kim, Seokhyeon;Cho, Jaepil;Lee, Jae Nam;Kang, Moon Seong
    • Journal of The Korean Society of Agricultural Engineers
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    • v.62 no.6
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    • pp.131-142
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    • 2020
  • The objective of this study was to evaluate future inundation risk of farmland according to the application of coupled model intercomparison project phase 5 (CMIP5) and coupled model intercomparison project phase 6 (CMIP6). In this study, future weather data based on CMIP5 and CMIP6 general circulation model (GCM) were collected, and inundation was simulated using the river modeling system for small agricultural watershed (RMS) and GATE2018 in the Tanjung district of the Moohan stream watershed. Although the average probable rainfall of CMIP5 and CMIP6 did not show significant differences as a result of calculating the probability rainfall, the difference between the minimum and maximum values was significantly larger in CMIP6. The results of the flood discharge calculation and the inundation risk assessment showed similar to trends to those of probability rainfall calculations. The risk of inundation in the future period was found to increase in all sub-watersheds, and the risk of inundation has been analyzed to increase significantly, especially if CMIP6 data are used. Therefore, it is necessary to consider climate change effects by utilizing CMIP6-based future weather data when designing and reinforcing water structures in agricultural areas in the future. The results of this study are expected to be used as basic data for utilizing CMIP6-based future weather data.

Analysis of Statistical Characteristics of Pier-Scour Depth Formula Using Hydraulic Experiment Data (수리모형실험 자료를 이용한 교각 세굴심 산정공식의 통계적 특성 분석)

  • Kim, Jong-Sub;Chang, Hyung-Joon
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.22 no.6
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    • pp.349-356
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    • 2021
  • Since the 1960s, traffic infrastructure, such as bridges, has increased rapidly in Korea as urbanization and industrialization progressed due to economic growth. As the scale of the bridge becomes larger, stability analysis of the superstructure of the bridge is being conducted actively, but scour stability analysis for the substructure of the bridge has not been conducted sufficiently. This study is a basic investigation to prevent large-scale disasters caused by scouring in bridge piers. A simple linear regression model was used to analyze the scour depth calculated through seventeen scour depth calculation formulae, and the scour depth measured through hydraulic model experiments. As a result, the Coleman (1971) formula was the best method among the scour depth calculation formulae, and the Froehlich (1987) formula was the most effective method for calculating the scour depth. In addition, a review using a simple regression model confirmed that the scour depth calculation formulae of CSU (1993), Coleman (1971), and Froehlich (1987) can predict a similar scour depth by reflecting domestic stream characteristics. This study can calculate the scour depth reflecting the environmental conditions of Korea in future stream design.

Chronological Study on the Deposits in Donggang Watershed(I) -Hierarchical Interpretation of River Topography using Remote Sensing Technique and GIS- (동강유역에 있어서 하상퇴적지의 연대학적 연구(I) -GIS와 원격탐사기법을 이용한 하천지형의 위계적 해석-)

  • Chun, Kun-Woo;Kim, Kyoung-Nam;Seo, Ok-Ha;Kim, Chang-Hwan
    • Journal of the Korean Association of Geographic Information Studies
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    • v.4 no.3
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    • pp.21-30
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    • 2001
  • This research was carried out for analyzing watershed and river topography. The method based on experience and map was mainly used, but derived data are too much to effectively analyze. Therefore some researchers have introduced computer system using GIS technique and remote sensing data. This research used GIS and remote sensing technique for classifying and analyzing watershed and river topography. Also dendrochronology method was introduced for guessing the creation times of deposits. Stream order map, sub-basin delineation map, river-bed microtopograpy were produced through this research. These results may be used in planning for Donggang conservation.

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