• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.34 no.1
• /
• pp.155-165
• /
• 2014

In this study, using a complex of physical, chemical, and biological evaluation factors, the ecological vulnerability to climate change were evaluated at each river in the Nakdong river basin. First, runoff, sediment rate, and low flow discharge changes according to AIB climate change scenario using the SWAT model were simulated. Also, for the assessment of chemical and biological factors, 48 points that water quality monitoring sites and ecological health measurement points are matched with each other was selected. The water quality data of BOD and T-P and the biological data of IBI and KSI in each point were reflected in the assessment. Also, the future rise in water temperature of the rivers in Nakdong river basin was predicted, and the impact of water temperature rise on the fish habitat was evaluated. The top 10 most vulnerable points was presented through a summary of each evaluation factor. This study has a contribution to river restoration or management plan according to the characteristics of each river.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.15 no.1
• /
• pp.23-33
• /
• 1979

This paper was analysed based on the oceanographic and meteorological data complied from 1971 to 1977 for that search relationships among the fluctuation of sea condition and weather condition, and the catch of anchovy. In the year when heat loss from the sea surface in winter was maximum(in 1974, 658 Iy), temperature of midwater in summer was lower 2~4\ulcornerC than normal year. While heat loss was minimum (in1973, 487 Iy), temperature of mid water was higher 2\ulcornerC. When temperature of mid water of southern coast from June to August was higher than normal year, anchovy was caught good deal, but that was lower than normal year was bad fishing. When it had much precipitation (in 1973, 256mm), plankton was checked maximum (12cc) and also the catch of anchovy too (11, OOOm/t). While precipitation was minimum (in 1976, 123mm), plankton (3cc) and anchovy (2, 800m/t) was a litle. If we calcalate heat budget in winter, we can forecast temperature of mid-water in summer of following year. Therefore we may be able to forecast catch anchovy.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2006.05a
• /
• pp.1333-1337
• /
• 2006

표층수를 주요 취수원으로 활용하는 우리나라의 경우 저수지 내 남조류 대발생시 주로 인공순환에 의한 제어방안을 적용하고 있다. 본 연구에서는 간헐식 폭기장치를 사용중에 있는 H호를 대상으로 식물플랑크톤 제어 효과를 평가하고, 이에 따른 식물플랑크톤의 수직적 분포와 선택 취수와의 연관성을 규명하여 정수장 유입 원수의 수질을 향상하고자 하였다. 2005년 H호의 남조류 농도는 최대 $1.2mg/m^3 $ 수준으로 낮은 분포로 조사되었다. 남조강에 대한 폭기 효과는 6월에는 워낙 그 농도가 낮아 효과 분석 자체가 무의미 하였으나, 10월에는 비영향지점 보다 영향지점의 최대 농도가 약 28% 저감되는 효과를 확인하였다. 조사 기간 중 가장 높은 농도를 보인 조류강은 Cryptophyta이었으며 6월9일에 약 $5mg/m^3$ 농도로 측정되었다. 10월6일에는 Diatom, Bluegreen, Green algae, Cryptophyta가 비슷한 농도 분포로 혼재된 양상을 보였다. 다른 조류강의 경우 조사 기간 중 $3mg/m^3$ 이하의 농도로 측정되었다. 취수탑을 중심으로 설치하여 운영하는 간헐식 폭기장치 1기의 유효 영향 범위를 조사하기 위하여 폭기 영향권에서 식물플랑크톤 분포를 submersible fluorescence probe로 현장에서 실시간으로 조사한 결과 식물플랑크톤 밀도는 감소하고 수직적인 분포층은 깊어지는 현상을 보였다. 이러한 효과를 보이는 거리는 폭기 장치로부터 약 50m로 나타났으며 pH, DO, 수온항목의 결과에서도 같은 현상을 보였다. 이 결과에 따르면 현재 설치된 총 7기의 폭기 장치의 유효영향 범위는 최대 $0.07km^2$ 면적에 그 효과를 기대할 수 있을 것으로 판단되어, 남조 수화현상이 심화될 경우 인공순환에 의한 저감효과가 크지는 않을 것으로 예측된다. 조사 기간중 H호의 현존 식물플랑크톤량의 $60%{\sim}87%$가 수심 10m 이내에 분포하였고, 녹조강과 남조강이 우점하는 하절기에는 5m 이내에 주로 분포하였다. 취수탑 지점의 수심이 연중 $25{\sim}35m$를 유지하는 H호의 경우 간헐식 폭기장치를 가동하는 기간은 물론 그 외 기간에도 취수구의 심도를 표층 10m 이하로 유지 할 경우 전체 조류 유입량을 60% 이상 저감할 수 있을 것으로 조사되었다.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.46 no.5
• /
• pp.582-588
• /
• 2013

The impact of global warming on aquatic systems has been a priority research area in the past decade. However, the possibility that increased temperatures will cause shifts in viral disease outbreaks has not been well addressed. In the present study, with increasing water temperature (WT) in the coastal area of Korea, we estimated the possibility of changes in fish viral diseases. From the present time, WT may rise between 0.62 and $1.7^{\circ}C$ by 2050, and the effect on aquaculture could be more adverse than benefitial. Red seabream iridovirus disease (RSIVD) and viral nervous necrosis (VNN) cause high mortality above 22 and $24^{\circ}C$, respectively, and outbreaks could commence earlier and persist for prolonged periods. Nevertheless, the period of occurrence of viral hemorrhagic septicemia (VHS), which outbreaks at a lower WT (< $18^{\circ}C$), could be shorter than the current infectious period. Thermal stress in fish causes reductions in growth and immunocompetence; thus, increases in summer WT can lead to the development of new viral diseases. WT has a strong influence on fish population dynamics; therefore, entry of new viruses and changes in the prevalence of infection can be expected if carrier fishes are introduced or migrate to Korean waters.

• Journal of Korean Society on Water Environment
• /
• v.30 no.6
• /
• pp.673-682
• /
• 2014

A watershed model was constructed using Hydrological Simulation Program Fortran to predict the water temperature at major tributaries of Nakdong River basin, Korea. Water temperature is one of the most fundamental indices used to determine the nature of an aquatic environment. Most processes of an aquatic environment such as saturation level of dissolved oxygen, the decay rate of organic matter, the growth rate of phytoplankton and zooplankton are affected by temperature. The heat flux to major reservoirs and tributaries was analyzed to simulate water temperature accurately using HSPF model. The annual mean heat flux of solar radiation was estimated to $150{\sim}165W/m^2$, longwave radiation to $-48{\sim}-113W/m^2$, evaporative heat loss to $-39{\sim}-115W/m^2$, sensible heat flux to $-13{\sim}-22W/m^2$, precipitation heat flux to $2{\sim}4W/m^2$, bed heat flux to $-24{\sim}22W/m^2$ respectively. The model was calibrated at major reservoir and tributaries for a three-year period (2008 to 2010). The deviation values (Dv) of water temperature ranged from -6.0 to 3.7%, Nash-Sutcliffe efficiency(NSE) of 0.88 to 0.95, root mean square error(RMSE) of $1.7{\sim}2.8^{\circ}C$. The operational water temperature forecasting results presented in this study were in good agreement with measured data and had a similar accuracy with model calibration results.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2011.05a
• /
• pp.213-213
• /
• 2011

남강은 낙동강에 유입되는 지류 중 가장 큰 하천으로서 낙동강 하류의 수질에 매우 큰 영향을 미치고 있다. 남강댐은 저수 용량에 비해 유역면적이 주요 저수지들에 비하여 월등하게 크므로 홍수시 순간적으로 다량의 유량 및 오염물질이 방류되어 낙동강에 유입되는 특성을 가지고 있다. 남강댐은 서북측에서 유입되는 경호강과 남쪽에서 댐축과 가까이 유입되는 덕천강이 공간적으로 멀리 떨어져 있음으로 인해, 주요 유입물질이 유입되는 시기에 횡방향 및 종방향으로 농도차이를 나타내고 있으며, 과거에 설치되었던 댐이 수중에 존재함으로 인해 국지적인 정체현상이 발생하고 있다. 남강은 현재 경남권은 물론, 거제 및 부산권의 용수원을 공급하거나 예정으로 있으므로 수질관리에 가장 큰 우선순위를 두어야 한다. 남강댐의 합리적인 수질관리를 위해서는 호 내의 공간적 시간적 수질변화에 대한 이해와 수질변화 여건에 있으며 이용되는 만큼 호 내의 정밀한 유체거동 해석이 필수적이다. 본 연구에서는 남강댐의 수리-수질 특성을 진단하고 예측하기 위하여 3차원 수리동역학 모델인 EFDC와 수질모델인 WASP을 연계하여 사용하였다. 유량 경계조건은 한국수자원공사 및 국가수자원관리 종합 정보시스템(WAMIS)의 남강댐 운영 자료를 바탕으로 남강댐의 유입량과 유출량 자료를 작성하였다. 남강으로 유입되는 지천 및 호 내의 수온, SS 및 수질농도 등은 환경부의 물환경정보시스템의 월 측정자료를 사용하였으며, 기상조건은 진주 기상대의 자료를 사용하였다. 본 연구에서 가용한 입력자료를 이용하여 남강댐의 수리 및 수질 및 부유물질 특성을 모의하였으며 EFDC-WASP 모델을 이용하여 성공적인 보정이 가능한 것을 확인하였다. 그러나 자세한 분석과 대책을 수립하기 위해서는 남강댐의 유입 수질 및 유량 자료에 대한 실질적인 모니터링이 수행되는 것이 필요하다고 판단된다.

• Journal of Korean Society for Geospatial Information Science
• /
• v.19 no.4
• /
• pp.3-12
• /
• 2011

Understanding of water sediment trends is an important part of water quality monitoring. Water quality variables change over time and space, and cannot be modeled or explained clearly by either temporal or spatial analysis alone. This research analysed the trends of temperature, pH levels and dissolved oxygen levels based on the sediment records and spatial data obtained in Lower Mekong Basin (LMB) during 1985-2005. Our aim is to evaluate spatio-temporal trends and graphical analyses using an Inverse Distance Weighting (IDW) interpolation method. The main results from this research can be summarized as follows. The maximum temperature and pH have been stable during the study period and the maximum dissolved oxygen has been increasing gradually until 2002. The minimum pH and dissolved oxygen have been changing in an unsteady trend during the period. A spatial analysis shows that the water temperature in this region has been increasing over time. The pH trend shows that it is decreasing during 1993-2005. Dissolved oxygen concentration has been increasing from 1989 onwards and stays in that track.

• Korean Journal of Ecology and Environment
• /
• v.34 no.2 s.94
• /
• pp.81-89
• /
• 2001

In order to know relationships between green euglenoids and environmental factors, the species composition and density were assessed for 12 months together with environmental variables in the Jeonjucheon urban drainage, Korea. Nitrate was a high of 3.22 mg/1 in June and phosphate concentration was over 0.71 mg/l in the winter. The euglenoids totaled 5 genera and 71 species throughout the year, increasing in the early summer (35 to 42 texa) and decreasing in the winter (below 20 taxa). The number of green euglenoids positively correlated with surface water temperature. the total density of the green euglenoids showed a typical bimodal pattern, being maximal in the winter (5,394 cells/ml in June). The winter peak was a result of active growths of Euglena caudata, E. geniculata and E. viridis, however, each of which positively correlated with the phosphate. The early summer peak was attributed to Euglena deses, Lepocinclis ovum, and Phacus trypanon, each of which positively correlated with the ammonium and nitrate. The complete bimodal spectrum of species number and density of green euglenoids provides a sensitive image in detecting the changes of environmental variables in polluted waters such as Jeonjucheon.

• Journal of Korean Society on Water Environment
• /
• v.30 no.5
• /
• pp.491-502
• /
• 2014

As meteorology is the driving force for lake thermodynamics and mixing processes, the effects of climate change on the physical limnology and associated ecosystem are emerging issues. The potential impacts of climate change on the physical features of a reservoir include the heat budget and thermodynamic balance across the air-water interface, formation and stability of the thermal stratification, and the timing of turn over. In addition, the changed physical processes may result in alteration of materials and energy flow because the biogeochemical processes of a stratified waterbody is strongly associated with the thermal stability. In this study, a novel modeling framework that consists of an artificial neural network (ANN), a watershed model (SWAT), a reservoir operation model(HEC-ResSim) and a hydrodynamic and water quality model (CE-QUAL-W2) is developed for projecting the effects of climate change on the reservoir water temperature and thermal stability. The results showed that increasing air temperature will cause higher epilimnion temperatures, earlier and more persistent thermal stratification, and increased thermal stability in the future. The Schmidt stability index used to evaluate the stratification strength showed tendency to increase, implying that the climate change may have considerable impacts on the water quality and ecosystem through changing the vertical mixing characteristics of the reservoir.

• Journal of Korea Water Resources Association
• /
• v.49 no.9
• /
• pp.789-798
• /
• 2016

Frequent algal blooms at major river systems in Korea have been serious social and environmental problems. Especially, the appearance of cyanobacteria with toxic materials is a threat to secure a safe drinking water. In order to model the behaviour of cyanobacteria cell number, an exclusive causality analysis using prewhitening technique was introduced to delineate effective parameters to predict the cell numbers of cyanobacteria in Seungchon Weir and Juksan Weir along Youngsan river system. Both input and output transfer function models were obtained to explain temporal variation of cyanobacteria cell number. A threshold behaviour of water temperature was implemented into the model development to consider winter characteristic of cyanobacteria. The implementation of water temperature threshold into the model structure improves the predictability in simulation. Even though the input output transfer model cannot completely explained all blooms of cyanobacteria, the simple structure of model provide a feasibility in application which can be important in practical aspect.