• KCID journal
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• v.18 no.1
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• pp.33-43
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• 2011

Jundae reservoir has basin area of 234ha, average depth of 3.77m and total storage of $619{\times}10^3m^3$, and is located in Dangin-gun, Chungcheongnam-do. The water quality of Jundae reservoir exceeded the IV grade of water quality standard as available for irrigation water in COD, TN, TP, Chl-a. COD and Chl-a were higher in spring season, because the algal bloom by phytoplankton increased. And the algal blooms in October by inflow non-point pollution during summer rainy season. The most dominant zooplankton was rotifers during study period at all stations. Dominant species were Keratella cochlearis, Polyarthra spp., and Trichocerca spp. We successfully established 2 isolated clone cultures as predator. One is Rotifer, Euchlanis sp. and another is cladocerans, Bosmina sp. To test the removal rate of 2 cultures against Microcystis aeruginosa, we inoculated Euchlanis sp. and Bosmina sp. separately when the abundance reached at $1.0{\times}10^6$cells/ml. Euchlanis sp. removed M. aeruginosa around 98.9% and Bosmina sp. removed it around 98.4%. They are useful grazers for controling algae blooms, Euchlanis sp. and Bosmina sp. feeding on M. aeruginosa highly.

• Water for future
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• v.9 no.2
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• pp.67-75
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• 1976

With 9 existng reservoirs selected in the Sab-Gyo River Basin, the sedimentation of the reservoirs has been calculated by comparing the present capacity with the original value, which revealed its reduced reservoirs capacity. The reservoirs has a total drainage area of 6,792 ha, with a total capacity of 1,204.09 ha-m, and are short of water supply due to reduction of reservoirs capacity. Annual sedimention in the reservcire is relation to the drainage area, the mean of annual rain fall, and the slop of drainage area. The results of obtained from the investigation are summarized as follow; (1) A sediment deposition rate is very high, being about $9.19{m}^3/ha$ of drainage area, and resulting in the average decrease of reservoir capacity by 19.1%. This high rate of deposition could be mainly attributed to the serve denvdation of forests due to disor derly cuttings of tree. (2) An average unit storage of 415.8mm as the time of initial construation is decreesed to 315.59mm at present, as resultting, we could'nt supply water at 566.24ha. (3) A sediment deposition rate as a relation to the capacity of unit drainage area is as follow; $Qs=1.43 (c/a)^{0.531}$ (4) A sediment deposition rate as a relation to the mean of annval rainfall is as follow; $Qs=672.61 p^{0.024}$ (5) A sediment deposition rate as a relation to the mean slop of drainage area is follow; $Qs=267.21 S^{0.597}$

• The Journal of Engineering Geology
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• v.28 no.4
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• pp.541-552
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• 2018

The implementation of drought measures in the upstream areas of river basins is seldom considered with respect to water supply. However, the demand for such measures is increasing rapidly owing to the occurrence of severe droughts, and interventions on streams and the water supply are needed. Physical interventions are an option to prevent streams from becoming dry and to maintain stream water flow, but dam construction is challenging because of environmental and ecological considerations. Here, a feasibility study was conducted to assess the potential effects of sand dams, which are widely used in arid regions in Africa. The SWAT-K model, which is a hydrologic model used for Korean watersheds, is used to estimate the flow rate of water in an ungauged watershed. The changes in water storage of the sand-dammed reservoir and in downstream flow rates are estimated for two types of sand dam (natural and dredged). The results show that sand dams are capable of increasing the downstream flow rate during normal conditions and of mitigating water supply problems caused by the withdrawal of water during drought periods.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.5B
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• pp.415-429
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• 2011

Quantitative evaluation indexes for flood control effect of a multi-purpose reservoir used widely in Korea are the discharge control rate, reservoir release rate, reservoir storage rate, and flood control storage utilization rate. Because these indexes usually use and compare inflow, release, and storage data directly, the uncertainties included in these data are not considered in evaluation process, and the downstream flood control effects are not assessed properly. Also, since the acceptable partial failure in a design of water resources system is not considered, the development of a new flood control effect evaluation index is required. Fuzzy set theory is therefore applied to the development of the index in order to consider the data uncertainty, the downstream flood control effect, and the acceptable partial failure. In this study, the flood control effect of a multi-purpose reservoir is evaluated using the flood control effect index developed by applying fuzzy set theory. The Chungju reservoir basin was selected as a study basin and the storm events of July, 2006 are used to study the applicability of the developed index. The related factors for flood control effect are fuzzified, the acceptable failure region is divided from the system state to evaluate the flood control effect using developed flood control effect index. The flood control effect index were calculated by applying to the study basin and storm events. The results show that the developed index can represent the flood control effect of a reservoir more realistically and objectively than the existing index.

• Journal of Wetlands Research
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• v.21 no.spc
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• pp.80-89
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• 2019

The purpose of this study is to analyze the relationship between SPI (Standardized Precipitation Index) meteorological drought and RDI (Reservoir Drought Index) agricultural drought for Geum river basin. Drought Indices was calculated by collecting data of precipitation and agricultural reservoir water storage rate from 2014 to 2016. To evaluated the correlation between meteorological and agricultural drought, the Pearson correlation and the Receiver Operation Characteristic (ROC) analysis were conducted to evaluate the correlation between meteorological and agricultural droughts. The SPI-6 and RDI showed the highest relationship with Pearson coefficient 0.606 and ROC hit rates 0.722 respectively, and the spatial occurrence patterns of drought using overlapped SPI-6 and RDI, the big differences between the 2 indices were occurred in the upstream areas of Miho stream and Nonsan stream from August to October 2015. The analysis using reservoirs specifications for areas where reservoir droughts occurred was conducted, and the areas showing severe drought of RDI were the reservoir areas having relatively small value of basin magnifying power (BMP). This means that a reservoir has the reaction capability for agricultural drought mainly depending on the reservoir BMP.

• 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 the Korean earth science society
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• v.43 no.1
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• pp.110-118
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• 2022

Frequent drought damage has resulted in the polarization of water resources. In Korea, local periodic abnormal droughts continued to occur between 2011 and 2017, resulting in decreased water storage rates of small-scale reservoirs designed with a frequency of 10-year droughts. This decrease can degrade water quality and limit the use of already secured quantities. Therefore, to prepare for and overcome drought, quality management and recalculation of drought frequency are required. This study estimates the potential pollutants causing quality changes in the reservoir. In addition, it reviews the decrease in storage and consequent changes in the quality of a reservoir during drought.

• Korean Journal of Ecology and Environment
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• v.47 no.spc
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• pp.57-65
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• 2014

Spatial and temporal distributions of zooplankton were measured in an oligotrophic pumped storage-type hydroelectric reservoir which was composed of two reservoirs exchanging water daily, with water going up at night and going down during the day. Repetitive diel disturbance of the water column can be a unique feature of this reservoir system. Chl-${\alpha}$ concentration was highest in the early winter season. Phytoplankton density was lower in summer monsoon due to high flushing rate on rainy days. The zooplankton density was higher in the smaller upper reservoir possibly due to lower fish density in the upper reservoir. In the seasonal variation a time gap was observed between the phytoplankton bloom and the zooplankton bloom (particularly a rotifer, Keratella cochlearis). It is likely to that Keratella production is partially supported by heterotrophic food sources than phytoplankton. The dominance of a mixotrophic dinoflagellate (Peridinium bipes f. ocultatum) might have complicated the trophic relationship between phytoplankton and zooplankton. Our results provide some ecological information of zooplankton community in a highly disturbed alpine reservoir ecosystem relying on mostly allochthonous organic matter.

• Journal of the Korean Association of Geographic Information Studies
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• v.19 no.1
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• pp.64-79
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• 2016

The purpose of this study is to find the relationship between precipitation deficit, SPI(standardized precipitation index)-12 month, agricultural reservoir water storage deficit and agricultural drought-related big data, and to evaluate the usefulness of agricultural risk management through big data. For the long term drought (from January 2014 to September 2015), each data was collected and analysed with monthly and Provincial base. The minimum SPI-12 and maximum reservoir water storage deficit compared to normal year were occurred at the same time of July 2014, and August and September 2015. The maximum frequency of big data was occurred at June and July of 2014, and March and June to September of 2015. The maximum big data was occurred 1 month advanced in 2014 and 2 months advanced in 2015 than the maximum reservoir water storage deficit. The occurrence of big data was sensitive to spring drought from March, late Jangma of June, dry Jangma of July and the rainfall deficit of September 2015. The big data was closely related with the meteorological drought and agricultural drought. Because the big data is the in situ feeling drought, it is proved as a useful indicator for agricultural risk management.

• Korean Journal of Agricultural Science
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• v.38 no.1
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• pp.163-172
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• 2011

To provide the operation rule curve for suppling instream flow to urban stream from reservoir, the Soho reservoir with watershed area of 7.4 $km^2$ and total water storage of 2.58 $Mm^3$ was planned at the headwaters of the Daejeoncheon. Daily streamflow was simulated and using the simulated streamflow and desired instream flow, the operation rule curve by Senga method was drawn and evaluated through reservoir operation. Senga method is derived by accumulating the differences between streamflow and desired instream flow adversely. Water storages were simulated on a daily basis to supply urban instream flow from Soho reservoir, but the amount of supplying instream flow to urban stream was not nearly increased comparing with that of normal operation that does not used the rule curve. Thereafter the new simulation-based operation rule curve was derived and applied to supply instream flow from Soho reservoir. In normal operation, the amount of instream flow was shown to 15,000 $m^3$/d, but it was increased to 27,700 $m^3$/d in withdrawal limited operation using the new derived rule curve, in which the applicability of this rule curve was proved. Also comparing with the flow duration curves at station just before urban Daejeoncheon stream without and with upstream Soho reservoir, the 95th flow was decreased from 1.64 mm/d to 1.51 mm/d, and the 355th flow was increased from 0.17 mm/d to 0.30 mm/d. Monthly streamflows during October to March were increased from 10.6~24.1 mm to 24.1~34.0 mm with the increasing rate of 141~227%.