• Journal of Korean Society on Water Environment
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• v.28 no.4
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• pp.551-560
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• 2012

The objectives of this study were to elucidate spatio-temporal heterogeneity of water chemistry and develop empirical models using trophic variables in Daechung Reservoir during 2005-2010 along with in situ tests of nutrient enrichment bioassays (NEB). The relations of water quality parameters in regard to precipitation showed that seasonal and interannual fluctuations of biological oxygen demand (BOD), total nitrogen (TN) and pH were minor, whereas conductivity, suspended solids (SS), and total phosphorus (TP) were largely varied in response to the magnitude of rainfall. The CHL maxima occurred immediately after the spate of TP during the high flow, indicating that phytoplankton growth was directly controlled by phosphorus. Empirical linear models of CHL-TP indicated that the variation of CHL in premonsoon was accounted 60% ($R^2$ = 0.60, p < 0.05, n = 54) by TP. In the mean time, empirical models of annual CHL-TN showed that the variation of CHL was weakly accounted ($R^2$ = 0.16, p < 0.001) by TN and more strongly ($R^2$ = 0.44, p < 0.001) by TP. Thus, the variation of CHL was more explained by the variation of TP than TN. In situ tests of Nutrient Enrichment Bioassays (NEBs) showed that the growth of CHL was greater in the P-treatments (as $PO_4-P$) than the control and N-treatment (as $NO_3-P$). Overall, our results suggest that phosphorus was aprimary limiting nutrient controlling the seasonal phytoplankton growth, based on the in situ experiments of NEBs.

• Journal of Korean Society on Water Environment
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• v.26 no.6
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• pp.895-902
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• 2010

The effect of seasonality on water quality variation is very significant. Generally, it reduce the power of the trend extraction. A parametric time-series model was used for detecting trends in historic constituent concentration data. The effect of seasonality is able to remove from time series decomposition technique. According to such statistic methode, long-term water quality trend analysis system (NTrend 1.0) was developed by Nakdong River Water Environmental Research Center. The trend analysis of BOD variation was conducted with NTrend 1.0 at Goreong and Moolkum site in Nakdong river to show the effect of water quality management action plan. Power test of trend extraction was tried each case of 'deseasonalized and deannulized' data and 'deseasonalized' data. Analysis period was from 1989 to 2006, and it's period was divided again three times, 1989~1993, 1994~1999 and 2000~2006 according to action plan period. The BOD trend was downward in Goreong site during three times and it's trend slope was very steep, and upward in Moolkum during 1989~1993, but it was turned downward during 1994~1999 and 2000~2006. It was revealed that it's very effective to reduce the concentration of BOD by water quality management action plan in that watershed. The result of power test was shown that it is high for trend extraction power in case of 'deseasonalized' data.

• Journal of environmental and Sanitary engineering
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• v.19 no.3 s.53
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• pp.1-12
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• 2004

This study was conducted to evaluate the variation characteristics of influent and effluent quality from sewage treatment facilities using activated sludge processes and to assess the impact caused by discharge of treated sewage on the receiving water Monthly data of five water quality items (BOD, COD, SS, T-N, T-P) were used to understand the water quality at three sewage treatment plants in Seoul for five years from 1999 to 2003. Concentration differences of water quality parameters were observed between upstream and downstream site at the sewage treatment plant outfall to investigate the impact of discharge in Tan stream and Han river basin. 1. Due to the effect of continuous improvement in sewer system, the concentrations of influent went on increasing generally. 2. Effluent concentrations of BOD, COD and SS showed the trend of a little decreasing, but the trend of increasing in T-N and T-P. 3. In Tan stream basin, the impact of sewage treatment plant discharge was not observed directly, because concentration of discharge was lower than stream water's. But discharges from sewage treatment plants affected water quality at downstream site in Han river, concentration of T-P especially.

• The Journal of the Korea Contents Association
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• v.13 no.5
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• pp.485-492
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• 2013

The point sand bars of Hahoi Village on Nakdong River have undergone considerable changes including fluvial and vegetation characteristics due to flood regulation by the dams constructed upstream. In this study, the numerical fluvial/sediment and water quality model, KU-RLMS, is applied to the aquatic area near Hahoi Village (middle/upper region of the Nakdong River) for clarifying the mechanisms of changes in hydraulic and aquatic characteristics. The fixed-bed hydraulic experiment was carried out for horizontal two-dimensional numerical model. The numerical simulation reveals that flow is accelerated near the left bank of Booyongdae downstream of the Hahoi Village area. Circulatory flow pattern was observed at the right bank downstream of Hahoi Village. The simulation was in good agreement with the hydraulic/physical experiment. For the discharge of design flood, at the area of circulatory flow pattern, the superelevation of about 1.0 m at the right bank was predicted compared to the left bank of high flow velocity, which is also in good agreement with hydraulic experiment.

• Journal of Environmental Science International
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• v.19 no.11
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• pp.1445-1456
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• 2010

This study presented seasonal changes of the phytoplankton community in Junam reservoir by pollution and water quality of the lake. The water storage of the reservoir is 5.3 million ton, most of which are being utilized for agricultural, industrial and residential purposes. The annual precipitation during the investigation period was 1,868.9 mm, increasing by 20% from the average annual level of 1,506.7 mm in 2009. The annual average water storage was 57.3%. It decreased during agricultural season and then increased again after monsoon rainfall. The loads of BOD were $3,799kgday^{-1}$, and 81% of them came from livestock and household. The TN and TP loads were $1,164kgday^{-1}$ and $170kgday^{-1}$, respectively, and 76% of them came from livestock. We assessed water quality of the Junam reservoir using 17 variables. According to the result, the reservoir met the fourth grade, meaning slightly bad, because of high concentration of COD, SS and chlorophyll-a. Eutrophication assessment was conducted by revised Carlson's Index (TSIm, Aizaki), and it was found that the entire lake was eutrophicated with high chlorophyll-a concentration all through the year, except during February to April and in July. A total of 76 phytoplankton species were identified from the samples. Among them, the largest number of species were Chlorophyceae with 33 species(43.4%), followed by Bacilliophyceae with 27 species(35.5%), Cyanophyceae with 8 species(10.5%), and Cryptophyceae with species(10.5%). The total cell number of phytoplankton was the highest in October(7,884 cells $mL^{-1}$) among Cyanophyceae and Bacilliophyceae. The seasonal succession of Chlorophyceae (Chlamydomonas spp.), Cyanophyceae(Microcystis aeruginosa) and Cryptophyceae(Rhodomonas spp.) was observed during January to May, July to September and October to December respectively.

• Journal of Environmental Science International
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• v.9 no.1
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• pp.1-11
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• 2000

A study on the variational characteristics of water quality and phytoplankton biomass by principal component analysis(PCA) was carried out in Kogum-sudo from February to October in 1993. We analyzed PCA on biological factors such as chlorophyll a and phytoplankton cell numbers for centric and pennate diatoms, phytoflagellates, and total phytoplankton as well as physico-chemical factors as water temperature, salinity, transparency, dissolved oxygen(DO), saturation of DO, apparent oxygen utilization (AOU), chemical oxygen demand(COD), nutrient (ammonia, nitrite, nitrate, phosphate and silicate), N/P ratio and suspended solid(SS). The source of nutrients supply depended on the mineralization of organic matters and inputs of seawater from outside rather than runoff of freshwater. The phytoplankton biomass was changed within short interval period by nutrients change. And it was controlled by the combination of several environmental factors, especially of light intensity, ammonia and phosphate. The marine environmental characteristics were determined by the mineralization of organic matters in winter, by runoff of freshwater including high nutrients concentration in spring, by ammonia uptake and high phytoplankton productivity in summer, and phosphate supplied input seawater from outside of Kogeum-sudo in autumn. And Kogum-sudo was separated with 2 regions by score distributions of PCA. That is to say, one region was middle parts of straits which was characterized by the mixing seawater and the accumulated organic matters, other one region was Pungnam Bay and the water around Kogum Island which was done by high phytoplankyon biomass and productivity year-round.

• Journal of Korean Society on Water Environment
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• v.22 no.2
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• pp.342-348
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• 2006

Changes in water quality and algal growth according to the differences in the inflow volume were investigated in the Daecheong Lake from 1998 to 2001. Until year 2000, inflow volume considerably depended on the rainfall throughout the basin. However, the correlation was low since 2001 when water storage in the upstream Yongdam Lake was started. According to inflow volume-TP relationship analyses, significant correlation was found at up- and middle-stream sites, excluding down-stream site of the Daechong Lake. For chlorophyll-a, correlation was found with flow volume at all sites except for Choo-So. In a dry year, although nutrients loads were relatively lower than those in rainy years, there were higher concentrations of chlorophyll-a and massive bloom of Microcystis. Limiting factors for algal growth seems to be not the volume of nutrients load but retention time and physical disturbance of the water body influenced by inflow volume. Thus, in the Daecheong lake, it would be more important to focus on the management of eutrophication in dry years than in rainy ones.

• Journal of Korean Society on Water Environment
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• v.23 no.6
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• pp.889-896
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• 2007

From the direct outflow of Chungju Dam to the junction of water body and watershed in Paldang lake is the scope of this research. This study performed to investigate the main cause of water quality deterioration and the influenced region in the middle field range of the Namhan river Basin with the onsite measurement of water quality and flow rate simultaneously during spring dry season. The purpose of this study is to find out the time-spatial variation characteristics of water quality and flow rate. Following the flow direction $BOD_5$ and $COD_{Mn}$ concentration increased to the highest value of 3.7 mg/L, 5.9 mg/L at Wolgesa respectively. Chl.a concentration increased to $50mg/m^3$ or so at Kangsang, after that it decreased to $37mg/m^3$ at the junction of Paldang lake. Organic matter concentration variation trend showed similar than that of Chl.a. Also $BOD_5$ concentration tendency was similar to Chl.a in every measuring sites except Paldang lake mixing zone. The major factors of water quality deterioration in Namhan river and Paldang lake during dry season were algal bloom and followed internal production. High phosphorus load from Dalcheon and Seom river caused dry season algal bloom and internal production in transitional zone which was stagnant area in downstream of Namhan river.

• Journal of Korean Society on Water Environment
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• v.29 no.1
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• pp.97-106
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• 2013

The temporal and spatial variations of water quality in a stratified reservoir are fully dependent on the characteristics of inflow loading from its watershed and the transport regimes of pollutants after entering the reservoir. Because of the meteorological and hydrological conditions in Korea, the pollutants loading to reservoirs are mostly occur during rainfall events. Therefore it is important to understand the characteristics of pollutants loading from upstream rivers and their spatial propagation through the stratified reservoir during the rainfall events. The objectives of this study were to characterize the water quality variations in upstream rivers of Imha Reservoir during a rainfall event, and the transport and spatial variations of pollutants in the reservoir through extensive field monitoring and laboratory analysis. The results showed that the event mean concentration (EMC) of SS, BOD, $COD_{Mn}$, T-N, T-P, $PO_4-P$ are 8.6 ~ 362.1, 2.5 ~ 5.1, 1.5 ~ 5.1, 1.1 ~ 1.9, 8.3 ~ 57.1, 5.6 ~ 25.7 times greater than the mean concentrations of these parameters during non-rainfall period. The turbidity and SS data showed good linear correlations, but the relationships between flow and SS showed large variations because of hysteresis effect during rising and falling periods of the flood. The ratio of POC to TOC were 12.6 ~ 14.7% during the non-rainfall periods, but increased up to 28.2 ~ 41.7% during the flood event. The turbid flood flow formed underflow and interflow after entering the reservoir, and delivered a great amount of non-point pollutants such as labile and refractory organic matters and nutrients to the metalimnion layer of reservoir, which is just above the thermocline. Spatially, the lateral variations of most water quality parameters were marginal but the vertical variations were significant.

• Proceedings of the Korea Water Resources Association Conference
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• 2004.05b
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• pp.1072-1076
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• 2004

도시 개발에 의해 우수의 불투수지역 확대, 하천부지의 축소, 산림 및 유수지의 감소 등이 급속히 진행되어 하천유량의 변화, 지하수위의 저하, 용수의 고갈, 생태계의 파괴 등이 발생되어 왔다. 도시지역은 도시형 수해발생, 갈수시의 급수안전도 지하, 평시 하천유량의 감소, 공공수역의 수질악화, 지하수 오열 등 여러 가지 문제에 직면하고 있다. 이러한 문제들은 서울의 경우도 예외는 아니며 청계천 복원 사업과 더불어 그동안 방치되었던 도시유역의 물순환 체계를 분석할 필요가 있다. 본 연구에서는 SWAT 모형을 이용하여 도시하천 유역의 물순환을 해석하였다. SWAT모형은 미국 농무성 농업연구소(Agricultural Research Service, ARS)에서 개발된 모델로서, 내규모의 복잡한 유역에서 장기간에 걸친 다양한 종류의 토양과 토지이용 및 토지관리 상태에 따른 물과 유사 및 농업화학물질의 거동에 대한 토지관리 방법의 영향을 예측하기 위해 개발되었다. SWAT 모형은 물리적 이론에 근거한 연속모형으로 준분포형 (Semi-Distributed) 모형이다. 본 연구는 도시하천 유역의 물순환체계 변동을 고려한 물순환 정상화 기술을 개발하기 위한 기초단계로서, 청계천 유역에 내해 모형을 적용하였다. 청계천은 중랑천의 제1지류인 지방2급 하천으로 유역면적 $50.96km^2$, 유로연장 13.75km이며, 2003년 7월부터 ,5.9km의 본류구간에 대한 복원공사가 진행 중이다. 적용유역의 수문${\cdot}$기상${\cdot}$지하수 자료는 1993널 1월 1일 $\~$ 2002년 12월 31일까지의 서울 기상청 자료를 이용하였으며, 지형, 토양, 토지이용 자료는 기존에 구축된 GIS 자료를 이용하였다. 모형 적용결과, 도시하천 유역에 대한 SWAT 모형의 적용성을 확인할 수 있었으며 유역의 물순환계를 구성하는 강수, 지표수, 토양수, 지하수 및 하천수 등의 상호 관계 분석을 통해 장기간의 유역 물순환체계 변화를 분석할 수 있었다.