• KCID journal
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• v.17 no.2
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• pp.95-104
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• 2010

Water quality data for 10 years (2000~2009) from about 826 reservoirs that are operated as a agricultural water quality survey network were analyzed in order to seek water quality management plan based on physical and chemical characteristics of agricultural reservoirs. The 95% reservoirs that exceed agricultural water quality standard of Chl-a (35mg/ $m^3$) had effective water depth shallower than 5m. The reason was that the reservoirs had more inflows of nutrient salts from the watershed, bigger surface water area of weak structure to algae occurrence. As the reservoirs of effective water depth shallower than 5m cover 49% of benefited area for irrigation, it is critical for agricultural water quality management of the reservoirs. The water quality of reservoir with shallower than 5m effective water depth was worse than reservoir with deeper than 5m effective water depth. Therefore, it is desirable that effective water depth of reservoirs make more than 5m for water quality management by building the bank higher and dredging the bottom of reservoirs.

• Journal of the Korean Geosynthetics Society
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• v.12 no.3
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• pp.81-86
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• 2013

The object of this study is to determine checklists of agriculture reservoirs which local government managed at routine inspection by Analysis Hierarchy Process (AHP). Suggest definition of agriculture reservoirs and distinguish type of destruction of reservoirs through the analysis of domestic reservoirs or overseas. Draw damage factors of reservoirs from survey on specific area. Combine type of destruction and damage factors of reservoirs for decision of evaluation type of reservoirs. Then, determine optimized routine inspection checklists for agriculture reservoirs and reservoirs by means of AHP considering a weighting.

• Journal of Korean Society on Water Environment
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• v.29 no.1
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• pp.81-87
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• 2013

Changes of organic carbon after the entrance into dam reservoirs were investigated using water samples collected in May, September, and October in 2010 from the inflow sites and the outlets of four selected dam reservoirs-Soyang, Chungju, Chungju regulation, and Uiam. Increase of refractory dissolved organic carbon (R-DOC) was observed only for large dam reservoirs with long residence times whereas the trend was not found for relatively small reservoirs. The effects of residence times on organic carbon changes were further confirmed by significant positive correlations between monthly residence times and the relative increase of either dissolved organic carbon (DOC) or R-DOC concentrations. Comparison of spectroscopic characteristics of DOC revealed that the changes in the large reservoirs in May might result from in-lake processes. The inflow of terrestrial sources of DOM during storms appears to largely affect the DOC quality of the large reservoirs for the rest of the sampling periods. The mechanism, however, did not fully explain the behaviors of DOC for the small sized reservoirs. Our combined results suggested that both residence time and the input of allochthonous carbon sources might substantially influence the quantity of DOC as well as its quality in dam reservoirs.

• Journal of Korean Society on Water Environment
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• v.24 no.3
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• pp.333-339
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• 2008

This study was carried out to assay the relationships between empirical factors and water quality in 23 agricultural reservoirs. Based on the trophic state index (TSI) deviation analysis, phosphorus in type II and III was the primary limiting factor on algal growth. BOD, COD, TP and chl.a concentration in type III reservoirs showed higher concentration than those of other types, while SS and TN concentration was no noticeable difference among three types. Characteristics of type III reservoirs showed large reservoir surface and drainage area, large surface area to volume (SAV) ratio, small drainage area to reservoir area (DA/RA) ratio, relatively old age, large paddy field and upland field to drainage area ratio (Mean 17.4%) and high generation and discharge loads compared to other types of reservoirs. In type I and II reservoirs, trends of BOD, TN, TP concentration in water column, were similar to those of the discharge load of pollutants. Although type II reservoirs generally showed low phosphorus discharge loads compared to type I reservoirs, TP and chl.a concentration in water column was greater than that of type I. Characteristics of type II reservoirs showed relatively large SAV ratio and old age compared to type I reservoirs and was similar to those of type III including eutrophic reservoirs.

• Journal of Korean Society on Water Environment
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• v.25 no.3
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• pp.386-393
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• 2009

This study was carried out to assess water quality and to introduce the management measures for water quality improvement with the collected data from 87 agricultural reservoirs in Han river watershed. According to the water quality criteria (WQC) for lake based on the COD, TP, TN and chl.a concentration, 18, 16, 4 and 19 of 87 reservoirs exceed class IV, respectively. Based on the trophic state index (TSI) with chl.a concentration, 51 of selected reservoirs appeared to be eutrophic. Phosphorus was limiting nutrient on algal growth in 58 reservoirs. TP, chl.a and COD concentration in 23 of 49 agricultural reservoirs with chl.a concentration ${\geq}25{\mu}g/L$ and eutrophic exceed class IV by WQC. Also, the mean depth in 21 of 23 reservoirs was below 5m. Our results suggest that advanced wastewater treatment and crop land control in watershed of reservoirs with TP concentration ${\geq}0.1mg/L$ would be a effective tool to improve water quality. Dredging would to be effective measure in reservoirs with mean depth < 5 m and relatively old age. In reservoirs with chl.a concentration ${\geq}50{\mu}g/L$, application of technique such dissolved air flotation (DAF) and P inactivation be effective to improve water quality by removing particulate matters in water column. The management measure to control inflow such as sedimentation basin, Pre-dam and diversion would to be application in reservoirs with shallow depth, while large watershed and surface area.

• Korean Journal of Ecology and Environment
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• v.47 no.3
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• pp.146-159
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• 2014

In this study, we evaluated the temporal changes of water quality in the 90 reservoirs in Korea and the relationships between water quality and their environmental factors in the reservoirs for effective management of reservoirs. The majority of study reservoirs were categorized as the eutrophic state based on Carlson's trophic index. Among 90 reservoirs, more than 55.0% were nutrient-rich based on $TSI_{TP}$ in each month, where more than 50.0% were nutrient-rich based on $TSI_{Chl-a}$ from June to November. Seasonal Mann-Kendall test was used to analyze temporal variation of water quality in the selected 60 reservoirs using monthly data from 2004 to 2008. The results showed that 27 (45.0%) reservoirs showed the improvement of water quality based on TP and Chl-a concentrations, while 14 (23.3%) and 11 (18.3%) reservoirs displayed the degradation of water quality based on TP and Chl-a concentrations, respectively. Meanwhile, a self-organizing map classified the study reservoirs into five groups based on differences of hydrogeomorphology (altitude, catchment area, bank height, lake age, etc.). Physicochemical factors and land use/cover types showed clear differences among groups. Finally, hydrogeomorphology of reservoirs were related to water quality, indicating that the hydrogeomorphological characters strongly affect water quality of reservoirs.

• Journal of Korean Society of Water and Wastewater
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• v.18 no.3
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• pp.366-376
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• 2004

Use of artificial circulation system has become popular in Korean reservoirs to control algal blooms and subsequent color, taste and odor problems in drinking water. It was found that the most of aeration system in Korean reservoirs are under-designed compared to existing installations in US and Australia. This was especially true for larger reservoirs greater than $5{\times}10^7m^3$ in volume since it is common to install the system in the vicinity of intake areas only. Consequently, successful cases of artificial circulation systems operations are limited to few small reservoirs less than $1{\times}10^7m^3$. It is suggested that the design methods need to be developed considering physical characteristics and water quality kinetics inside of reservoirs. Also operation methods of artificial circulation systems need to be established considering the water quality dynamics, stratification and morphological characteristics of reservoirs. Finally, it is suggested to maintain comprehensive and long term monitoring programs to validate the application of artificial circulation system in reservoirs.

• KCID journal
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• v.17 no.2
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• pp.17-27
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• 2010

In order to manage the water quality in reservoir, it is necessary to understand the temporal and spatial variation of reservoirs and to classify the reservoirs. In this research, agricultural reservoirs are classified according to physical characteristics (depth, residence time, shape of the reservoir etc) and water quality using multivatriate analysis (PCA and CA). CA (Cluster Analysis) method classify reservoirs into several groups as a similarity of the reservoirs, but it is difficult to indicate a full list to the one table. In case of PCA (Principle Component Analysis) method, it has the advantage for the classification on the reservoirs depending on the water quality similarity and also it is useful to analyze the relationship between related factors through correlation analysis. However PCA is limited to classify into several groups based on the characteristics of the reservoirs and each user should be classified as randomly subjective according to the relative position of the reservoir in the figure. In conclusions, compared to conventional reservoirs classification methods, both CA and PCA methods are considered to be a classification method that describes the nature of the reservoir well, but classification results has a restriction on use, so further research will be needed to complement.

• Korean Journal of Agricultural Science
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• v.43 no.2
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• pp.258-274
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• 2016

Recently, as fluctuations in annual precipitations continue to grow, the frequency of floods and droughts is rapidly increasing. Especially, since many reservoirs are reported as having less capacity and aging faster than large dams, the damages due to floods and droughts are estimated to become more severe. With this background for the present study, field investigation of reservoirs in Chungnam, Chungbuk, and Chonbuk regions was carried out for disaster prevention and the safety management of agricultural reservoirs. Furthermore, embankment transformations were compared and analyzed after the raising of embankments. Based on design methods for remodeling agricultural reservoirs and the results of embankment raising and the problems which occurred on crest, supplementation to the upstream and downstream slopes, control sector, and spillway should be implemented in the existing reservoir. In regard to this, the condition assessment score of compound member of reservoirs was performed, the Chungnam region score was in the 3.11-4.73 range. In addition, reservoirs in Chungbuk scored in the 4.00-4.49 range, and reservoirs in Chonbuk scored in the 3.90-4.60 range. Applying current precision safety inspection practices to small reservoirs requires economic expenses and time, for which assessment items are too varied and complex. Therefore, subdivided condition assessment items and criteria should be improved and streamlined by deleting, reducing, combining, and selecting only the riskiest factors. In the future, reservoirs should be periodically monitored and systemically managed and rational plans for maintenance and repairs should be used as reinforcement methods.

• Journal of The Korean Society of Agricultural Engineers
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• v.50 no.3
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• pp.51-58
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• 2008

Ninety five percent of the agricultural reservoirs were constructed by earth or rock. There are 18,000 agricultural dams and reservoirs in Korea. Therefore, it is easy to evaluate or identify their problems. Reservoirs should be repaired before too late. It is required to guarantee the proper functions of the existing agricultural dams and reservoirs in time to minimize the damage. In this study, in order to evaluate degradation of agricultural reservoir, grasps the safety of reservoir choosing for agriculture of 25 reservoirs which are distributed in Chungbuk region rural and analyzed using possibility as reservoir of agricultural usage. The degradation was evaluated by a compilation of the result where embankment and structure were separately handled, measured and then multiplied scores for each categories. By activating this research, current status of agricultural reservoir and degradation status will be easily measured. In addition, the research could be also used as a tool for an effective control or maintenance.