• Korean Journal of Ecology and Environment
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• v.45 no.3
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• pp.329-339
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• 2012

In the spring (March to June) in 2010, one diatom Skeletonema costatum occurred outbreaks in Lake Hwajinpo, one of the typical lagoons on the east coast of South Korea. We compared the characteristics of the phytoplankton community during the bloom and extinction period of S. costatum, and evaluated the water quality based on nutritional indices. Results indicate that 1) this bloom showed the highest cell density ($>10^5$ cells $mL^{-1}$) among outbreaks of S. costatum occurred Korea, 2) occurred in below or over $20^{\circ}C$ water temperature, and 3) was destroyed in the early summer with higher temperature than the bloom period. Water quality or trophic status of the lake was eutrophic to hypertrophic with high salinity, BOD, COD and phosphate, and low N/P ratios and transparency. Phytoplankton community in the spring bloom had a high dominance and low diversity, but rightly recovered to low dominance and high diversity in the summer season. Therefore, we temporarily conclude that the bloom of S. costatum in Hwajinpo was triggered by the extended spring drought and the reduced influx of river water, and appeal that the bloom can happen repeatedly every year.

• Korean Journal of Ecology and Environment
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• v.43 no.3
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• pp.349-355
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• 2010

This study aims at the augmentation of reliability of the long-term rainfall runoff model. To do so agricultural water uses are evaluated by analyzing the effects of small scale irrigational hydraulic structures on long term runoff processes and thereby rainfall-runoff model is modified considering them. As a result the simulation results of the sub-basins having more agricultural reservoirs than the others are disagreed with the observations. The 2nd quarter simulation results show similar trend to it. Especially the farming seasonal results of the drought year as the year of 2008 have many negative discharge values due to the lack of agricultural water uses. This result come from the water uses input data corresponding to not real water uses but water demands. In this study the formulas are derived to estimate the discharges and return ratios and the long term rainfall-runoff model is reformulated based on these. It is confirmed that the errors of the simulation results could be reduced by considering the effects of small scale irrigational hydraulic structures and the reliability of the simulation results improved greatly.

• Korean Journal of Ecology and Environment
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• v.40 no.2
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• pp.327-336
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• 2007

This study assessed ecological health using a multi-metric fish model from 15 sites in the headwater watershed of southern Han River during June${\sim}$August 1999 and then compared the health with conventional community diversity index to figure out differences between health and diversity index. For the analysis, we adopted 10 metric IBI model for regional applications. During this survey, total number of species sampled were 24 (6 families) and varied depending on magnitude of ecological disturbance and stream order. In the mountainous streams, mean proportion of sensitive and insectivore species was composed of 91% and 56%, respectively, indicating a potential healthy conditions. However, tolerant species with 66% and omnivore species with 76% were sampled from the 2nd order stream, which was shown deterioration in the physical habitat quality. In the overall watershed, mean IBI value was 38, judging as "fair" condition by the health criteria. Values of Individual IBI were closely associated with stream order and this pattern was similar to other mountainous streams showing low chemical pollutions and disturbance. Our comparison between IBI and diversity index over the stream order showed a distinct difference; Shannon-Weaver diversity index overestimated the actual community conditions and the variation range in the 2nd order stream was greater in the diversity index. Overall data suggest that the multi-metric approach may to a useful tool for stream ecosystem management and the conventional diversity index may not effective unless the stream order is considered for the stream evaluation.

• Journal of Wetlands Research
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• v.2 no.1
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• pp.19-29
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• 2000

The physico-chemical characteristics of core sediment, community dynamics of Salix species during the sedimentation were investigated in 1990~1997 for the purpose of inquiry to reveal the effects of terrestrialization on the environment and plant community in a natural wetland. The study site, Paksil-nup wetland was a valley blocked lake located near Hwang-River, Hapcheon-gun, Gyeongsangnam-do, Korea. The values of conductivity, organic matter, total nitrogen, exchangeable K, and exchangeable Ca were higher, and pH was lower in the upper layer of the core sediment. Soil properties such as available phosphorus, exchangeable Ca, exchangeable Na increased, and organic matter, total nitrogen, exchangeable K decreased during the sedimentation. Salix nipponica was the dominant species, and Salix glandulosa was subdominant among 10 Salix species. Sahx species were supposed to be the pioneer plants in shrub and tree layers during the succession in Paksil-nup wetland. Age class of SaliX species community from the epilittoral zone to the infralittoral zone were low, and age of Saljx species distributed from 2 years to 11 years. DBH, height, mean number of branches, number of herb species, and light intensity were increased, whereas density was decreased from a lower age to a higher age community. Salix nipponica was superior than Sahx purpurea var. japonica and other Salix species during the interspecific competition among Salix species.

• Journal of Korea Water Resources Association
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• v.45 no.5
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• pp.495-503
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• 2012

It is necessary to perform the precise analysis of unsteady flow for effective design of the side-weir detention basin installed in the river. Generally, the HEC-RAS program, which is a 1D unsteady numerical model, is mostly used to simulate the unsteady flow for rivers. However, it is difficult to have confidence of unsteady flow results simulated by HEC-RAS due to the lack of experimental data and field monitoring data for the channel with a side-weir detention basin. Therefore, the purpose of this study is to validate or verify the simulation results calculated by HEC-RAS through the experiments for the open channel with a side-weir detention basin using specially-designed unsteady discharge-supply system. The experimental cases included unsteady flows in the straight channel with and without a side-weir detention basin. Especially, for the case with a detention basin, the experiment was performed to consider only the free flow condition over the side-weir. The study results showed that values of water level and discharge obtained from HEC-RAS coincided reasonably with experimental results with the maximum error of 3% for water level and 1% for discharge in the case of the flow without the side-weir detention basin and 4% for water level and 2% for discharge with the side-weir detention basin.

• Journal of Korea Water Resources Association
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• v.45 no.11
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• pp.1131-1141
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• 2012

In this study, factors that influence water supply capacities of dams are extracted using factor analysis, and multiple regression equations for estimating water supply capacities of dams are developed using the analysis results. Twenty-one multi-purpose dams and twelve Municipal and Industrial (M&I) water supply dams are selected for case studies, and eight variables influencing water supply capacities of dams, namely: watershed area, inflow, effective reservoir storage, grade on amount of M&I water supply, grade on amount of agricultural water supply, grade on amount of in-stream flow supply, grade on river administration, and grade on average rainfall, are determined. Two case studies for multi-purpose dams and M&I water supply dams are performed, employing factor analysis, respectively. For the two cases, preliminary tests, such as reviewing matrix of correlation coefficient, Bartlett's test of sphericity, and Kaiser-Meyer-Olkin (KMO) test, are conducted to evaluate the suitability of the variables for factor analysis. In case of multi-purpose dams, variables are grouped into three factors; M&I water supply dams, two factors. The factors are rotated using Varimax method, and then factor loading of each variable is computed. The results show that the variables influencing water supply capacities of dams are reasonably selected and appropriately grouped into factors. In addition, multiple regression equations for predicting the amounts of annual water supply of dams are established using the factor scores as explanatory variables, it is identified that the models' accuracies are high, and their applications to determining effective storage capacity of a dam during dam planning and design steps are presented. Consequently, it is thought that the variables and factors are useful for dam planning and dam design.

• Korean Journal of Ecology and Environment
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• v.39 no.3 s.117
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• pp.285-295
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• 2006

Korean water quality standards for the protection of agricultural water uses were originally derived based on management of public water resource. They were not prepared to protect crop plants from contaminants, and therefore required water parameters in agricultural uses were excluded in current water quality standards. Korean water standards in river and lake have five levels, and level IV is correspondent to agricultural water uses. Currently, there is no Korean guidelines to protect crop plants from contaminants contained in agricultural water. In Canada, agricultural water guidelines are provided to protect crops from contaminants. In this study, agricultural water quality standards in Korea were compared with them in developed countries to evaluate the adequacy of Korean water quality standards for the protection of agricultural water uses. Additional water quality parameters in agricultural uses were also proposed. Suggested parameters include electric conductivity, sodium, chloride, boron, copper, iron, zinc, and microbiological quality, They are the required parameters to protect crop plants as well as human health. Current water quality standards in agricultural uses was not considered to be appropriate in terms of crop protection. Additional water parameters should be included in agricultural water quality standards.

• Korean Journal of Ecology and Environment
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• v.39 no.3 s.117
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• pp.310-319
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• 2006

The objective of study was to evaluate ecological health from seven sampling locations of Yoogu Stream, one of the tributaries of Guem River, July and September 2005. The research approach was based on the Index of Biological Integrity (IBI) using fish assemblage and Qualitative Habitat Evaluation Index (QHEI) using fish assemblage. The models of IBI and QHEI were modified as 10 metric model and 11 metric model, respectively, for the regional applications. In Yoogu Stream, value of IBI were averaged 29.5 (n=7) which is judged as a 'fair condition'. The IBI model scores, at the site 3 and 7, were estimated as 23 and 24, indicating a 'poor${\sim}$fair condition' while, site 5 was estimated as 28, 'fair condition'. The remaining sites were between 31 and 34, indicating 'fair${\sim}$good condition'. According to the analysis of QHEI, the average was estimated as 136, 'fair${\sim}$good condition'. Spatial variation the QHEI were evident; site 1 and site 4 were 186 and 120 respectively, indicating an 'excellent and fair${\sim}$good conditions'. Site 3 was 69, fair condition while the other sites were 128${\sim}$156, good condition.

• Journal of Environmental Science International
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• v.20 no.7
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• pp.819-828
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• 2011

This research was done to clarify the cooling effect of water particles generated from a fountain. This effect is a one way to control the heat island effect of big cities. The result of this research was drawn by setting the jets of water in a certain height, and then studying the diffusion of water particles, which is affected by the size of the particles and the wind speed, and the cooling effect caused by the diffusion. 1) When a diameter of a water drop was 500 ${\mu}m$ and the wind speed was 2.0 to 6.0 m/sec, the water drop diffused 75 to 190m, and the water vapor spread over 175 to 440 m. As a result, there was more than $0.5^{\circ}C$ of cooling effect on the temperature in the atmosphere 130 to 330m around the water fountain. 2) When a diameter of a water drop was 750 ${\mu}m$ and the wind speed was 2.0 to 6.0 m/sec, the water drop diffused 65 to 150 m, and the water vapor spread over 160 to 405 m. Moreover, there was more than $0.5^{\circ}C$ of cooling effect on the temperature in the atmosphere 110 to 275 m around the water fountain. 3) After studying on the relationship between the diameter of water drop and the wind speed, and the diffusion of water particles and the range of the atmosphere that was cooled, a result could be drawn from the research that the smaller the diameter of the water vapor gets and the faster the wind speed becomes, the wider the water particles diffuse and the cooler the atmosphere around the fountain becomes. 4) This research further extrapolates that when the ordinary water(tap water, water from river and stream) is used in a fountain, the cooling effect of the air near the fountain can be approached similarly. If the seawater is used in a fountain, there is to be more to concern not only on cooling effect on the air, but also on other effects on surrounding environment generated by the salt in seawater.

• Journal of the Korean Institute of Landscape Architecture
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• v.28 no.2
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• pp.109-109
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• 2000

This study seeks what kind of factors influence to locate dwellings and to establish scenic spots in nature by a case study focused on a meandering stream. The study specially concentrates on the interrelationship between both residences and beautiful sceneries and a meander cut-off-area that reveals a special topographical characteristics, located at Samji village in Youngyang-eup, Youngyang-gun, Koungsangbuk-do. The meander cut-off area, developed at the middle or upper reaches of a river, often makes up specific landscapes such as precipitous cliffs, sheer cliffs and caves. And the area where is specially created by sudden change of flow due to erosion perceived by the cut surface to be the most beautiful scenic spot. These beautiful landscapes were used to be called as Dae, Dam or Gul and managed by Confucian scholars who enjoy refined taste and devote themselves to the study in nature. Moreover, the Ku-Hado-literary means the area of ex-flow-made the scholars' lving with a well prepared basis for agriculture where supplied a cornucopia of organic matters and water. The merit of agriculture made it possible that the scholars became economically independent, and the fact might be the essential point why the meander cut-off area took noticed. Actually, Cho-family has been in Smaji Village for generations, producing a large number of scholars and keeping the actual power of the region. The physical shape of the meander cut-off area, cozily surrounded by mountains, is considered as a good place for the dwelling due to the influence of traditional sight of view for location and P'ungsuchiri which is known as Feng Shui in China and geomancy in the western world. It is a fruit in it own way that we could find the ancestors' discernment and wisdom from this study, who have lived their lives adapting themselves to the given natural environment and also utilizing the nature wisely. But this is a current-argued study on the meander cut-off area. Follow-up studies have to be continued about the landscapes of the meander streams and the meander cut-off areas scattered all over the country except Samji Village and draw the characteristics from the comparative analysis.