• Journal of Environmental Impact Assessment
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• v.20 no.4
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• pp.435-442
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• 2011

In this study, a regression model was developed for prediction of inflow temperature to support an effective thermal stratification simulation of Yongdam Reservoir, using the relationship between gaged inflow temperature and air temperature. The effect of reproductability for thermal stratification was evaluated using EFDC model by gaged vertical profile data of water temperature(from June to December in 2005) and ex-developed regression models. Therefore, in the development process, the coefficient of correlation and determination are 0.96 and 0.922, respectively. Moreover, the developed model showed good performance in reproducing the reservoir thermal stratification. Results of this research can be a role to provide a base for building of prediction model for water quality management in near future.

• Water Engineering Research
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• v.7 no.1
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• pp.29-41
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• 2006

The Imha watershed is vulnerable to severe erosion due to the topographical characteristics such as mountainous steep slopes. Sediment inflow from upland area has also deteriorated the water quality and caused negative effects on the aquatic ecosystem of the Imha reservoir. The Imha reservoir was affected by sediment-laden density currents during the typhoon 'Maemi' in 2003. The RUSLE model was combined with GIS techniques to analyze the mean annual erosion losses and the soil losses caused by typhoon 'Maemi'. The model is used to evaluate the spatial distribution of soil loss rates under different land uses. The mean annual soil loss rate and soil losses caused by typhoon 'Maemi' were predicted as 3,450 tons/km2/year and 2,920 ton/km2/'Maemi', respectively. The sediment delivery ratio was determined to be about 25% from the mean annual soil loss rate and the surveyed sediment deposits in the Imha reservoir in 1997. The trap efficiency of the Imha reservoir was calculated using the methods of Julien, Brown, Brune, and Churchill and ranges from 96% to 99%.

• Journal of The Korean Society of Agricultural Engineers
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• v.55 no.6
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• pp.167-175
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• 2013

The objective of this study was to investigate the nutrient load balance in the reservoir irrigated paddy block during growing seasons. Idong reservoir irrigation paddy block of 10.3 ha in size was selected to collect hydrologic and water quality data. Irrigation, canal flows, and paddy field drainage were measured using a water level gauge, while water samples were collected and analysed for water quality. The water balance analysis showed that 81 % and 75 % of total outflow were through paddy and irrigation canal drainage during 2011 and 2012, respectively. The water quality of paddy field drainage varied greatly depending on rice cultivation stage ranging from 0.05 to 24.55 mg/L and from 0.01 to 0.76 mg/L for T-N and T-P, correspondently. Paddy field drainage loads during May through June account for 64 % and 76 % in 2012 and 2013, while 82 % and 81 % for T-P in 2011 and 2012, respectively. The Pearson correlation analysis showed that rainfall was significantly correlated with nutrient loads during July through August due to runoff, and irrigation was related with nutrient loads of drainage during some period of July through September due to irrigation return flow. This study results showed characteristics of inflow and outflow nutrient loads from plentiful irrigated paddy block.

• Journal of Microbiology and Biotechnology
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• v.16 no.7
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• pp.1060-1067
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• 2006

This study was undertaken to determine the effect of reservoirs on water quality and the distribution of pathogenic and indicator bacteria in a drinking water distribution system (total length 14km). Raw water, disinfected water, and water samples from the distribution system were subjected to physicochemical and microbiological analyses. Most factors encountered at each season included residual chloride, nitrate, turbidity, and phosphorus for heterotrophic bacterial distribution, and hardness, heterotrophic bacteria, sampling site, and DOC (dissolved organic carbon) for bacteria on selective media. No Salmonella or Shigella spp. were detected, but many colonies of opportunistic pathogens were found. Comparing tap water samples taken at similar distances from the water treatment plant, samples that had passed through a reservoir had a higher concentration of heterotrophic bacteria, and a higher rate of colony formation with 10 times as many bacteria on selective media. Based on the results with m-Endo agar, the water in reservoirs appeared safe; however, coliforms and opportunistic pathogenic bacteria such as Pseudomonas aeruginosa were identified on other selective media. This study illustrates that storage reservoirs in the drinking water distribution system have low microbiological water quality by opportunistic pathogens, and therefore, water quality must be controlled.

• Journal of Korea Water Resources Association
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• v.56 no.6
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• pp.419-429
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• 2023

The objective of this study was to determine the management water level of an estuary reservoir considering three aspects: the water use, flood control and water quality, and to use a robust decision-making to consider uncertainty due to climate change. The watershed-reservoir linkage model was used to simulate changes in inflow due to climate change, and changes in reservoir water level and water quality. Five management level alternatives ranging from -1.7 El.m to 0.2 El.m were evaluated under the SSP1, 2, 3, and 5 scenariosof the ACCESS-CM2 Global Climate Model. Performance indicators based on period-reliability were calculated for robust decision-making considering the three aspects, and regret was used as a decision indicator to identify the alternatives with the minimum maximum regret. Flood control failure increased as the management level increased, while the probability of water use failure increased as the management level decreased. The highest number of failures occurred under the SSP5 scenario. In the water quality sector, the change in water quality was relatively small with an increase in the management level due to the increase in reservoir volume. Conversely, a decrease in the management level resulted in a more significant change in water quality. In the study area, the estuary reservoir was found to be problematic when the change in water quality was small, resulting in more failures.

• Journal of the Korean Institute of Landscape Architecture
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• v.31 no.2
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• pp.102-112
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• 2003

This study was carried out to research and develop a shallow green rooftop system which would require low maintenance and therefore could be used for existing rooftops. To achieve these goals, the conceptual model was induced by past studies and the experimental systems were deduced from the conceptual model. On the growth of Sedum sarmentosum grown in these rooftop systems, the effects of artificial substrate type, soil depth, and drainage type were investigated from 3 April to 11 October 2002. Artificial substrates were an alone type and a blending type. The alone type was an artificial substrate formulated by blending crushed porous glass with bark(v/v, 6:4). The blending type was formulated by blending the alone type with loam(v/v, 1:1). Soil depths were 5cm, loom, and 15cm. Drainage types were a reservoir-drainage type and a drainage type. The reservoir-drainage type could keep water and drain excessive water at the same time. The drainage type could drain excessive water but could not keep water. Covering area, total fresh and dry weight, visual quality, and water content per 1g dry matter were measured. All the variables were analyzed by correlation analysis and factor analysis. The results of the study are summarized as follows. The growth increment was higher in the blending type than in the alone type, the highest in loom soil depth and higher in the reservoir-drainage type than in the drainage type. The growth quality was higher in the blending type than in the alone type, the highest in l0cm soil depth, and higher in the drainage type than in the reservoir-drainage type. In consideration of the permissible load on the existing rooftops and the effects of the treatments on the growth increment and quality, the system should adopt the blending type in artificial substrate types, 5~10cm in soil depths, and the drainage type in drainage types. This system will be well-suited to the growth of Sedum sarmentosum, and when the artificial substrate was in field capacity, the weight will be 75~115kg/$m^2$.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.12
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• pp.1331-1336
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• 2006

The Juam reservoir, hydrological investigations on the catchment environment and pollutants inflow have been carried out simultaneously. The average COD in 1992 observed in Juam reservoir was 2.3 mg/L, and reached to 2.72 mg/L in 2005 that is increased 0.23 mg/L for 13 years. Following this trend, the water duality is expected to deteriorate down to the second-grade water quality exceeding the 3 mg/L limit in 2010. The concentration exceeding the value of 46.5 $mg/m^3$ will not guarantee the water quality better than $2^{nd}$ grade drinking water resource since correlative between COD and chl-a is y=0.0732x+2.5953 its $r^2=0.8141$. This result will help control the algal growth in the future by taking into account the expected value as a monitoring target.

• Journal of Environmental Science International
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• v.23 no.7
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• pp.1321-1332
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• 2014

The key objective of this study was to evaluate trophic state and empirical water quality models along with analysis of fish trophic guilds in relation to water chemistry (N, P). Trophic state index (TSI), based on total phosphorus (TP) and chlorophyll-a (CHL), ranged between oligotrophic and hypereutrophic state, by the criteria of Nurnberg(1996), and was lower than the trophic state of total nitrogen (TN). Trophic relations of Secchi depth (SD), TN, TP, and CHL were compared using an empirical models of premonsoon (Pr), monsoon (Mo), and postmonsoon (Po). The model analysis indicated that the variation in water transparency of Secchi depth (SD) was largely accounted (p < 0.001, range of $R^2$ : 0.76-0.80) by TP during the seasons of Mo and Po and that the variation of CHL was accounted (p < 0.001, $R^2=0.70$) up to 70% by TP during the Po season. The eutrophication tendency, based on the $TSI_{TP}$ vs. $TSI_{N:P}$ were predictable ($R^2$ ranged 0.85-0.90, p < 0.001), slope and y intercept indicated low seasonal variability. In the mean time, $TSI_{N:P}$ vs. $TSI_{CHL}$ had a monsoon seasonality in relation to values of $TSI_{N:P}$ during the monsoon season due to a dilution of reservoir waters by strong monsoon rainfall. Trophic compositions of reservoir fish reflected ambient contents of TN, TP, and CHL in the reservoir waters. Thus, the proportions of omnivore fish increased with greater trophic conditions of TP, TN and CHL and the proportions of insectivore fish decreased with greater trophic conditions.

• Journal of the Korean Institute of Landscape Architecture
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• v.34 no.6 s.119
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• pp.1-9
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• 2007

Land use types within a watershed closely are related with the water quality characteristics of receiving water bodies. Despite of a numerous studies suggesting a strong relationship between water quality and land use, there have been increasing concerns about the geographical variation and a lack of spatial integration in that relationship, which are essential to implementing these findings into land use planning and management. In the meantime, edges mediate the material flux between adjacent systems. This mediating effect of edges is strongly related to the complexity of their shapes. Land use activities within a watershed have a direct impact on the water quality of adjacent aquatic systems, and hydrological processes carry residuals from watershed into adjacent aquatic ecosystems through the edges. Therefore, the geometry of reservoirs theoretically affects the relationship between land uses in the watershed and the quality of receiving bodies of water. In this light, this study integrates the geo-spatial dimensions of land uses in the watershed using GIS and landscape indices in order to explore the relationship between land uses and water quality. Water quality characteristics, land uses and geometry of 133 randomly sampled reservoirs were correlated, based on buffer zones and types of reservoirs. The findings showed that land uses, particularly urban land uses, significantly affect water quality characteristics including BOD, COD, TN and TP, and geometry of reservoirs reduces the concentration of pollutant and nutrients in reservoirs. One of results indicates that the relationship between land use and water quality and effects of spatial dimension may vary with types of reservoirs and pollutants. These results suggest that lakeshore areas are important, particularly for TN reduction and call for a caution to land use activities nearby shoreline areas for sustaining better water quality.

• Journal of Korean Society on Water Environment
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• v.18 no.3
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• pp.261-270
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• 2002

The artificial aeration in the middle and the small scale reservoirs is widely used to destroy the stratified layer and algal boom. This study has been conducted at the Youncho reservoir located in Keoje island since Jan. 2000 to suggest the most suitable control strategy of the artificial aeration and reduce the side effect. The main results obtained from this research are as follows. The starting time of aeration for destratification was adjusted from the end of March to the beginning of April when the natural stratification is started. In order to prevent an anoxic condition the artificial mixing should be started by the middle of April when the DO in hypolimnion is dropped to less than $5mg/{\ell}$. The decrease DO, caused by the increase in water temperature, spreads rapidly from hypolimnion to themocline. Thermal stratification disappeared after the onset of artificial aeration within 7 days in the Yuncho reservoir. The air diffusers decrease water temperature in the layer of epilimnion and thermocline, but rise it in hypolimnion. The continuous operation of air diffuser prevent the stratification and anoxic condition in hypolimnion despite of the rising of water temperature and algal abundance. The algal abundance is not observed in effective zone by aeration. The turbidity rising problem induced from the aeration is avoided by keeping an air diffuser about 1.5m high from the bottom of lake. During the summer season, ceasing the aeration should be decided carefully. And also, it is necessary to operate the system it considering weather and temperature, and depending on the number and the position of aerators.