• Title/Summary/Keyword: Surface discharge

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Estimation of Flood Flow and Inundation Range of the Aprokgang(Riv.) in 2024 using Satellite Images (위성영상을 이용한 2024년 압록강 홍수량 및 침수범위 추정)

  • Kim, Joo-Hun;Choi, Yun-Seok;Kim, Dong-Phil
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.44 no.5
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    • pp.673-681
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    • 2024
  • The purpose of this study was to estimate the flood flow and the range of inundation in the downstream area of the Aprokgang(Riv.) that occurred in 2024 using satellite images. The study area was the Aprokgang(Riv.) watershed, the longest river in North Korea. Satellite image Sentinel-1A(SAR-C) data was used for flood analysis before and after the flood. As a result of the analysis of the inundation range using satellite images, it was confirmed that there was a change in the water surface before and after the flood. However, the image after the flood was taken six days after the peak discharge of the flood, so there are limitations in extracting the accurate extent of the flooding. As a result of the analysis using satellite precipitation and ground observed rainfall, the rainfall exceeded 500-year rainfall amount, and the peak-flow was simulated as 85,102 m3/s. As a result of analyzing the inundation range by using the contour lines from AW3D30, it was determined that the inundation occurred around the 15 m contour line. In the future, it is need to conduct a study that can extract more scientifically the inundation range through the use of the inundation analysis model.

Seasonal Phytoplankton Growth and Distribution Pattern by Environmental Factor Changes in Inner and Outer Bay of Ulsan, Korea (울산만 내측과 외측에서 계절적 환경요인의 변화에 의한 식물플랑크톤 성장 및 분포)

  • LEE, MIN-JI;KIM, DONGSEON;KIM, YOUNG OK;SOHN, MOONHO;MOON, CHANG-HO;BAEK, SEUNG HO
    • The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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    • v.21 no.1
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    • pp.24-35
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    • 2016
  • To assess the relationship between environmental factors and seasonal phytoplankton community structure, we investigated abiotic and biotic factors in Ulsan Bay, Korea. We divided the bay into two areas based on geographical characteristics and compared the difference in each factor between inner and outer bay with t-test statistics. As a result, temperature in the outer bay was higher than that of the inner bay during winter (t = -5.833, p < 0.01) and autumn (p > 0.05). However, opposite trend was observed during spring (t = 4.247, p < 0.01) and summer (t = 2.876, p < 0.05). Salinity was significantly lower in the inner bay than in the outer bay in winter, spring, and summer (p < 0.01). However, the salinity was not significantly different between the inner and the outer bay in the autumn (p > 0.05). In particular, high nutrient concentration was observed in most stations during winter season due to vertical well mixing. The nutrient concentration was significantly higher in surface layers of inner bay after rainfall, particularly in the summer. The relative contribution (approximately 70%) of < $20{\mu}m$ (nano and pico) size phytoplankton was increased in all seasons with continuously low nutrients from the offshore water due to their adaption to low nutrient without other large competitors. Interestingly, high population of Eutreptiella gymnastica was kept in the inner bay during the spring and summer associated with high DIN (nitrate+nitrite, ammonium) after river discharge following rainfall, suggesting that DIN supply might have triggered the increase of Eutreptiella gymnastica population. In addition, high density of freshwater species Oscillatoria sp. and Microcystis sp. were found in several stations of the inner bay that were provided with large amounts of freshwater from the Tae-wha River. Diatom and cryptophyta species were found to be dominant species in the autumn and winter. Of these, centric diatom Chaetoceros genus was occupied in the outer bay in the autumn. Cryptophyta species known as opportunistic micro-algae were found to have high biomass without competitors in the inner bay. Our results demonstrated that Ulsan Bay was strongly affected by freshwater from Tae-wha River during the rainy season and by the surface warm water current from the offshore of the bay during dry season. These two external factors might play important roles in regulating the seasonal phytoplankton community structures.

On the High Yield Pulping of Fir by Pressurized Refining (가압(加壓)리화이닝법(法)에 의한 젓나무의 고수율(高收率)펄프 제조(製造)에 관한 연구(研究))

  • Cho, Nam Seok;Jo, Byoung Muk
    • Journal of Korean Society of Forest Science
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    • v.53 no.1
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    • pp.44-55
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    • 1981
  • Neutral sulfite precooked fir chips were refined in the Asplund Laboratory Defibrator at various temperature ($20^{\circ}C$, $120^{\circ}C$ and $180^{\circ}C$). The effects of refining temperatures on the physical property and morphological structure of the resulting pulps were discussed. Yields of precooked chips (84%, 92% and 100%) and refining temperature affected remarkably the yield of refined pulp, its beatability, sheet strength and morhphological characteristics. Pulp yield and beatability decreased with increasing refining temperature. Fiber surface of unbeaten pulp from precooked chips of 84% yield was to some extent covered by the secondary wall, while that of the pulp form precooked yield of 92% by the compound middle lamella. In the case of uncooked chips, fibers were damaged heavily, and the exposed fiber surface resulted from the equal amount of the secondary wall and the compound middle lamella. In the case of pulps prepared from precooked chips of higher yields (92% and 100%), sheet strength increased linearly as sheet density increased. But at the same sheet density, pulp from lower precooked yield (84%) had better sheet strength after open discharge refining as compared to pressurized refining, because pulp from the former had much amounts of fines fraction of higher water retention value than the latters. And there was observed a little difference in fiber length distribution but nearly similar in its morphology with increasing refining temperature.

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Evaluation of the Water Quality Changes in Agricultural Reservoir Covered with Floating Photovoltaic Solar-Tracking Systems (수상 회전식 태양광 발전시설 설치에 따른 농업용 저수지의 수질변화 평가)

  • Lee, Inju;Joo, Jin Chul;Lee, Chang Sin;Kim, Ga Yeong;Woo, Do Young;Kim, Jae Hak
    • Journal of Korean Society of Environmental Engineers
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    • v.39 no.5
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    • pp.255-264
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    • 2017
  • To evaluate the water quality changes in agricultural reservoir covered with floating photovoltaic solar-tracking systems, the water quality variations with time and depth were monitored on both six sites for light blocking zones and four sites for light penetration zones after the installation of floating photovoltaic solar-tracking systems in Geumgwang reservoir at Anseong-si, Kyeonggi province. For one year with 16 monitoring events, water quality parameters [i.e., water temperature, pH, dissolved oxygen (DO), chlorophyll-a (Chl-a), and blue-green algae (BGA)] were monitored at depths of 0.3 m, 1 m, 3 m, and 5 m, while chemical oxygen demand (COD), total nitrogen (TN), and total phosphorus (TP) were monitored at depths of 0.3 m. Statistically, the difference in all water quality parameters was not significantly different (p > 0.05) at the level of significance of 0.05. Based on these results, the water quality data from light blocking zones (site 1~6) and light penetration zones (site 7~10) were clustered, and were compared with time and depth. As a result, the difference in water temperature, pH, DO, COD, TN, TP, Chl-a, and BGA between light blocking zones and light penetration zones was not significant (p > 0.05) with different time and depth. For Chl-a and BGA, some data from light blocking zones greater than light penetration zones were temporary observed due to the severe drought, low water storage rate, and over growth of periphyton. However, this temporal phenomenon did not impact the water quality. Considering the small water surface area (${\leq}0.5%$) covered by floating photovoltaic solar-tracking systems, the mixing effect of whole Geumgwang reservoir caused by Ekman current and continuous discharge were more dominant than the effect of reduced solar irradiance. Further study is warranted to monitor the changes in water quality and aquatic ecosystems with greater water surface area covered by floating photovoltaic solar-tracking systems for a long time.

A Three-Dimensional Modeling Study of Lake Paldang for Spatial and Temporal Distributions of Temperature, Current, Residence Time, and Spreading Pattern of Incoming Flows (팔당호 수온, 유속, 체류시간의 시.공간적 분포 및 유입지류 흐름에 관한 3차원 모델 연구)

  • Na, Eun-Hye;Park, Seok-Soon
    • Journal of Korean Society of Environmental Engineers
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    • v.27 no.9
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    • pp.978-988
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    • 2005
  • A three-dimensional dynamic model was applied to Lake Paldang, Han River in this study. The model was calibrated and verified using the data measured under different ambient conditions. The model results were in reasonable agreements with the field measurements in both calibration and verification. Utilizing the validated model, we analyzed the spatial and temporal distributions of temperature, current, residence time, and spreading pattern of incoming flows within the lake. Relatively low velocity and high temperature were computed at the surface layer in the southern region of the Sonae island. The longest residence time within the lake was predicted in the southern region of the Sonae island and the downstream region of the South Branch. This can be attributed to the fact that the back currents caused by the dam blocking occur mainly in these regions. Vertical thermal profiles indicated that the thermal stratifications would be occurred feebly in early summer and winter. During early spring and fall, it appeared that there would be no discernible differences at the vertical temperature profiles in the entire lake. The vertical overturns, however, do not occur during these periods due to an influence of high discharge flows from the dam. During midsummer monsoon season with high precipitation, the thermal stratification was disrupted by high incoming flow rates and discharges from the dam and very short residence time was resulted in the entire lake. In this circulation patterns, the plume of the Kyoungan stream with smallest flow rate and higher water temperature tends to travel downstream horizontally along the eastern shore of the south island and vertically at the top surface layer. The model results suggest that the Paldang lake should be a highly hydrodynamic water body with large spatial and temporal variations.

The Study of Operating Conditions by Establishing Density Currents Generator for Improving of Water Quality on Lake Water - With Focus on DO and Water Temperature - (호소수의 수질개선을 위한 DCG 설치시 운전조건에 관한 연구 - DO와 수온을 중심으로 -)

  • Lee, Young-Shin;Han, Kyung-Hee;Kim, Young-Kyu;An, Hyung-Chul;Shin, Sung-Woo
    • Journal of Korean Society of Environmental Engineers
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    • v.36 no.4
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    • pp.286-294
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    • 2014
  • The purpose of this study is to investigate the effects of applying density current generator (hereafter referred to as DCG to large lakes on the operating conditions of DCG, de-stratification, water quality improvement and inhibition of algae occurrence. As a result of a survey conducted to derive the optimum operating parameters of DCG in a condition to minimize eco-toxicity, the following conclusions were obtained. During the survey period, a marked stratification appeared in September to October 2011 and May 2012. At this time, the average depth of water to form thermocline was found to be $5{\pm}2$ m, so the location of discharge port for the operation of DCG was determined to be about 5 m below from the surface. To minimize the adverse effects of benthos and obtain the effect of water mixture at the time of water circulation, the mixing ratio of surface water and deep water was designed to be 3:1 by means of ecotoxicological assessment on the DCG operating characteristics. To select the appropriate operating hours for DCG, DCG was operated by 12 hr, 24 hr, 36 hr and 48 hr. As its result, the formation of thermocline did not occur during the operation of 36 hr. Also, It was effected that start reoperating from 3rd day after stop 2days under the condition of operated during 36 hr with calculated power consumption. Under the above conditions, the results of DO and water temperature analysis during the operation of DCG showed that the stratification, which was distinct previously, appeared to be weak, and relatively lower levels than those before operation were found as a result of water quality analysis on COD and chlorophyll-a, which leads to the conclusion that the water body is maintained at a stable condition due to the circulation of water by the occurrence of density current resulting from the operation of DCG.

A Function and Weight Selection of Ecosystem Service Function for the Eco-friendly Protected Horticulture Complex in Agricultural Landscape (시설원예단지의 친환경적 조성을 위한 생태계서비스 기능 및 가중치 산정)

  • SON, Jinkwan;KONG, Minjae;SHIN, Yukung;YUN, Sungwook;KANG, Donghyeon;Park, Minjung;LEE, Siyoung
    • Journal of Wetlands Research
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    • v.19 no.4
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    • pp.533-541
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    • 2017
  • Agricultural landscape has many ecosystem service functions. However, the development of the horticulture complex has no consideration for environmental conservation. Therefore, we analyzed the priorities of ecosystem service functions required for the composition. The study was conducted in three stages. As a result of the first survey, 17 functions were selected to be improved. In the second survey, 12 functions were selected excluding 5 functions. Finally, 1. Measures for water purification, 2. Groundwater recharge plan, 3. Surface water storage space, 4. Flood control measures, 5. Vegetation diversity space, 6. Carbon emission reduction plan, 7. Aquatic insect habitat space, 8. Amphibian reptiles 9. Landscape and Waste Management, 10. Bird Species Space, 11. Heat Island Mitigation Plan, 12. Experience / Ecological Education Plan. We proposed the structure, capacity, flow rate, arrangement and form of the water treatment facility to improve water quality by improving the function. We proposed a reservoir space of 7-10% for groundwater recharge. The development of reservoir and storage facilities suitable for the Korean situation is suggested for the surface water storage and flood control measures. And proposed to secure a green space for the climate cycle. Proposed habitat and nutrient discharge management for biodiversity. We propose green area development and wetland development to improve the landscape, and put into the facilities for experiential education. The results of the research can be utilized for the development and improvement of the horticultural complex.

The characteristics of marine environment and phytoplankton community around southwestern waters for ichthyotoxic dinoflagellate Cochlodinium polykrikoides monitoring programme (남서해역의 유해성 적조생물 Cochlodinium polykrikoides Margalef 모니터링을 위한 환경특성 식물플랑크톤 군집 동태)

  • Cho Eun Seob;Choi Yong Kyu
    • Journal of Environmental Science International
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    • v.14 no.2
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    • pp.177-184
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    • 2005
  • This study was to determine the fluctuation in phytoplankton assemblages with regarding to environmental conditions and nutrients, which were surveyed around Mokpo waters in the southwestern waters, Korea. Sampling was carried out on the Mokpo, Sinan, and Wando coasts from March to November 2003. The maximum sea surface temperature was recorded in August, and it ranged around $25^{\circ}C$ regardless of sampling sites. However, salinity in Mokpo waters showed a great variation, which ranged from 5-30 psu and recoded the minimum of 5 psu in July and the maximum of 30 psu in November. Moreover, in Mokpo waters, the chlorophyll a and SS concentration of the surface layer were also the highest values of $20\;{\mu}g\;l^{-1}\;and\;40\;{\mu}g\;l^{-1}$, respectively than those of Sinan and Wando waters. The concentrations of $NH_4-N,\;NO_2-N,\;NO_3-N,\;and\;PO_4-P$ were also he highest values of $0.018\;{\mu}mol\;^l{-1},\;0.062\;{\mu}mol\;l^{-1},\;1.2\;{\mu}mol\;l^{-1}\;and\;0.078\;{\mu}mol\;l^{-1}$, respectively in Morpo waters than those of Sinan and Wando waters. During the period of this study, the majority of the taxa were diatoms; Thalassiosira rotula, Rhizosolenia setigera, Prorocentrum minimum, Chaetoceros curvisetus, Leptocylindrus danicus, Pseudonitzschia pungens, and Chaetoceros spp. were detected in the dominant species of phytoplankton. The dinoflagellates were relatively abundant during the summer season in Wando waters, which attained an abundance of $10-20\%$. In Mokpo waters, DIN/DIP was the highest value of 700 in March, whereas the lowest was shown in Wando waters. However, DIN/DIP value in summer at Wando waters was extremely reversed, which appeared to be associated with the development of dinoflagellates. On the bais of factor analysis using SYSAT 6.0, nutrient showed somewhat correlation with chlorophyll a. Consequently, the process of discharge of fresh water in Mokpo waters plays an important role in extremely fluctuation in nutrients and conditions. Although Wando waters maintains a lack of nutrients, it should be influenced by different water current and may be associated with a concentration of nutrients.

Temporal and Spatial Variation of Microalgal Biomass and Community Structure in Seawater and Surface Sediment of the Gomso Bay as Determined by Chemotaxonomic Analysis (색소분석을 통한 곰소만 내 해수와 퇴적물 중 미세조류 생체량과 군집구조의 시공간적 변화)

  • Lee, Yong-Woo;Park, Mi-Ok;Yoon, Ji-Hyun;Hur, Sung-Bum
    • The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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    • v.17 no.2
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    • pp.87-94
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    • 2012
  • To compare monthly variations of phytoplankton biomass and community composition between in seawater and sediment of the Gomso Bay (tidal flat: approximately 75%), the photosynthetic pigments were analyzed by HPLC every month in 1999 and every two months in 2000. Ambient physical and chemical parameters (temperature, salinity, nutrients, dissolved oxygen, and chemical oxygen demand) were also examined to find the environmental factors controlling structure of phytoplankton community. The temporal and spatial variations of chlorophyll a concentration in seawater were correlated well with the magnitude of freshwater discharge from land. The biomass of microphytobenthos at the surface sediments was lower than that in other regions of the world and 2-3 times lower than phytoplankton biomass integrated in the seawater column. Based on the results of HPLC pigment analysis, fucoxanthin, a marker pigment of diatoms, was the most prominent pigment and highly correlated with chlorophyll a in seawater and sediment of the Gomso Bay. These results suggest that diatoms are the predominant phytoplankton in seawater and sediment of the Gomso Bay. However, the monthly variation of chlorophyll a concentration in seawater at the subtidal zone was not a good correlation with that in sediment of the Gomso Bay. Although pelagic plankton was identified in seawater by microscopic examination, benthic algal species were not found in the seawater. These results suggest that contribution from the suspended microphytobenthos in the tidal flat to the subtidal zone of the Gomso Bay may be low as a food source to the primary consumer in the upper water column of the subtidal zone. Further study needs to elucidate the vertical and horizontal transport magnitude of the suspended microphytobenthos in the tidal flat to the subtidal zone.

The Influence of Nutrients Addition on Phytoplankton Communities Between Spring and Summer Season in Gwangyang Bay, Korea (광양만에서 춘계와 하계 영양염류 첨가가 식물플랑크톤군집의 성장에 미치는 영향)

  • Bae, Si Woo;Kim, Dongseon;choi, Hyun-Woo;Kim, Young Ok;Moon, Chang Ho;Baek, Seung Ho
    • The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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    • v.19 no.1
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    • pp.53-65
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    • 2014
  • In order to estimate the effect of nutrients addition for phytoplankton growth and community compositons in spring and summer season, we investigated the abiotic and biotic factors of surface and bottom waters at 20 stations of inner and offshore areas in Gwangyang Bay, Korea. Nutrient additional experiments were also conducted to identify any additional nutrient effects on phytoplankton assemblage using the surface water for the assay. Bacillariophyceae occupied more than 90% of total phytoplankton assembleges. Of these, diatom Eucampia zodiacus and Skeletonema costatum-like species was mainly dominated in spring and summer, respectively. Here, we can offer the season why the two diatom population densities were maintained at high levels in both seasons. First, light transparency of spring season in the euphotic zone was greatly improved in the bay. This improvement is one of important factor as tigger of increase in E. zodiacus population. Second, low salinity and high nutrient sources supplied by Seomjin River discharge are a main cue for strong bottom-up effects on S. costatum-like species during the summer rainy season. Based on the algal bio-assays, although maximum growth rate of phytoplankton communities at inner bay (St.8) were similar to those of outer bay (St.20), half-saturation constant ($K_s$) for phosphate at outer bay was slightly lower than those of inner bay. This implied that adapted cells in low nutrient condition of outer bay may have enough grown even the low phosphate and they also have a competitive advantage against other algal species under low nutrient condition. In particular, efficiency of N (+) addition in summer season was higher compared to control and P added experiments. In the bay, silicon was not a major limiting factor for phytoplankton growth, whereas nitrogen (N) was considered as a limiting factor during spring and summer. Therefore, a sufficient silicate supply form water mixing Si recycled from diatom decomposition and river water is favorable form maintaining diatom ecosystems in Gwangyang Bay.