• Journal of The Korean Society of Agricultural Engineers
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• v.51 no.5
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• pp.35-49
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• 2009

This study proposes a method to evaluate agricultural reservoirs drought by modifying SWSI (Surface Water Supply Index). The method was applied to Geum river basin and the results were represented as spatially distributed information. The SWSI evaluates hydrological drought of watershed unit by selectively applying one or all of the components of snowpack, precipitation, streamflow and reservoir storage. South Korea has 22 % of agricultural area, and rice paddy covers 64 % among them. Usually paddy fields scattered along stream are irrigated by so many small agricultural reservoirs. It is difficult to evaluate agriculture drought by the little information and large number of agricultural reservoirs. In this study, seven agricultural reservoirs over 10 million ton storage capacity were selected in Geum river basin, and the SWSI was evaluated for both upstream and downstream of the reservoirs using 16 years data (1991-2006). Using the results, multiple regression analyses with precipitation and reservoir storage as variables were conducted and the equations were applied to other watersheds. The spatial results by applying regression equations showed that the severe and moderate drought conditions of July and September in 1994, June in 1995, and May in 2001 were well expressed by the watershed unit.

• Magazine of the Korean Society of Agricultural Engineers
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• v.33 no.4
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• pp.52-60
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• 1991

This study was conducted to investigate the appropriate operation method minimizing the deviation between irrigation water demand and release from the reservoirs, and the simulation technique was used in the operation model. This model was applied to the grouped reservoirs system consisted of Dongsang, Daia and Keungchun reservoirs and Eowoo-weir in Chonbuk FLIA district. The results obtained in this study are summarized as follows; 1.The area above the Eowoo weir point was divided into 6 small watersheds, and daily inflows from each watershed were calculated by Tank model. It showed that the average annual runoff ratio was 40-60% respectively. 2.Based on the Blaney-Criddle formula daily water requirement of Chonbuk FLIA irrigation area was estimated, mean water requirement for paddy field during the irrigation period was 818.lmm. 3.Using the basic data such as inflow and water demand, four different release types were selected. Through the simulated operation the difference between intake water required at Eowoo-weir point and release from the 3 reservoirs was estimated. The best result was obtained when Daia and Keungchun reservoirs are operated parallelly at fixed release ratio and the release of Dongsang reservoir was determined according to the storage of Daia reservoir.

• Magazine of the Korean Society of Agricultural Engineers
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• v.44 no.3
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• pp.136-145
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• 2002

Monitoring data from agricultural reservoirs throughout the country were analyzed to evaluate the limiting factor fur algal growth and relationships between Chl-a, total phosphorus (TP), and total nitrogen (TN). Total 394 reservoirs ranging from below 500 ㎥ to over 50 million ㎥ in storage volume were monitored from 1990 to 2000 with respect to TP, W, Chl-a, and their annual mean values were used fur the analysis. Based on N/P ratio, the dominant limiting factor for algal growth was turned out to be phosphorus in agricultural reservoirs (about 83%). Therefore, the proper managements of phosphorus in the agricultural watershed appear to be crucial to prevent excessive on algal growth. The effects of phosphorus and nitrogen ware most eminent during the summer period. And the effect of nutrients on the algal biomass (Chl-a) development appeared to be greater in smaller the reservoirs than in larger ones. Generally, Chl-a and TP demonstrated a close relationship while that of Chl-a and TN showed less correlationship. Chl-a and chemical oxygen demand (COD) also showed a good relationship. Beth ratios of Chl-a / TP and Chl-a / COD relationships were within the range of literature values. Quantitative analysis of TP and COD is relatively convenient compared to that of Chl-a, and the relationship between TP and COD and Chl-a from this study could be used beneficially for water quality management of agricultural reservoirs and related water quality modeling.

• Journal of The Korean Society of Agricultural Engineers
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• v.59 no.3
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• pp.11-19
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• 2017

The decision-making process is the act of finding the best solution among various alternatives through comparison between various criteria based on objectives of the project, evaluation standard, and conditions. However, in practice it is not easy to simply decide the optimum decision, especially for selecting malfunctioning reservoirs because no systematic evaluation criteria or standard assessment process are available. Therefore, this study adopted AHP method, which is a MCDM (multi-criteria decision making technique) to identify the malfunctioning reservoirs for efficient management of reservoirs. Important criteria of the selection of malfunctioning reservoirs and priority weights of each criteria were determined based on results of expert's survey under a stepwise hierarchical approach. The most important factor for the decision of malfunctioning reservoirs was obtained as Reservoir efficiency among the selected criteria including Reservoir efficiency decrease, Disaster Risk, Reservoir efficiency, Available water storage, Future water demand, Resident Needs. The AHP technique was applied on 11 reservoirs in Andong region to verify its applicability. Scoring method was applied for the comparison with the results of AHP method.

• Korean Journal of Ecology and Environment
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• v.41 no.spc
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• pp.1-10
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• 2008

We patterned water quality of agricultural reservoirs according to the differences of six physico-chemical environmental factors (TN, TP, DO, BOD, COD, and SS) using four different ordination methods: Principal Components Analysis (PCA), Detrended Correspondence Analysis (DCA), Nonmetric Multidimensional Scaling (NMS), and Isometric Feature Mapping (Isomap). The data set was obtained from the water quality monitoring networks operated by the Ministry of Agriculture and Forestry and the Ministry of Environments. Chlorophyll-${\alpha}$ displayed the highest correlation with COD, followed by TP, BOD, SS, and TN (p<0.01), while negatively correlated with altitude and bank height of the reservoirs (p<0.01). Although four different ordination methods similarly patterned the reservoirs according to the gradient of nutrient concentration, PCA and NMS appeared to be the most efficient methods to pattern water quality of reservoirs based on the explanation power. Considering variable scores in the ordination map, the concentration of nutrients was positively correlated with Chl-${\alpha}$, while negatively correlated with altitude and bank height. These ordination methods may help to pattern agricultural reservoirs according to their water quality characteristics.

• Journal of The Korean Society of Agricultural Engineers
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• v.54 no.5
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• pp.17-24
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• 2012

The main purposes of the agricultural reservoir enlargement (ARE) project are to secure water supply reliability (WSR) for agriculture and to release environmental water during dry seasons. In this study, an operational rule that will simultaneously satisfy both the above issues was developed. Initial amount of water storage at the beginning of non-irrigation season (1st October) was divided into 3 stages, and the target level of water storage at the beginning of irrigation seasons (1st April) was set up. Required operational curves and release amounts were estimated based on the stages and target water levels. To evaluate the applicability of this rule, the amount of water released for environmental purposes and WSRs were analyzed for three reservoirs (Unam, Jangchi and Topjeong). The ratio between annual amount of release and additional amount of water storage were 1.6, 1.85, and 4.1 for the Unam, Jangchi, Tapjeong reservoirs, respectively. Also, the WSRs of all reservoirs were found to become higher than when the design standard was applied. Therefore, it is considered that the proposed rule is more suitable for the enlarged agricultural reservoirs operation as it satisfies the WSRs while securing the environmental water release.

• Korean Journal of Agricultural Science
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• v.38 no.2
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• pp.331-341
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• 2011

To provide variation of water supply for instream flow from reservoirs with various magnifications of paddy irrigation area to watershed area, 8 reservoirs were selected to draw operation rule curve and to analyze water supplies from reservoirs. Reliability of 90% for supplying irrigation water from reservoir was able to maintain and instream flow water was able to be supplied only in the reservoir with magnification of paddy irrigation area to watershed area above 3. The more magnification of paddy irrigation area to watershed area increased, the more ratio of irrigation water to total water storage decreased, and the more ratio of instream flow water to total water storage increased. From the heightening 113 reservoirs in Korea, annual irrigation water was estimated to 1,146.05 $Mm^3$ in normal operation, 839.57 $Mm^3$ in withdrawal limited operation, and annual instream flow water was estimated to 149.68 $Mm^3$ in normal operation, 283.19 $Mm^3$ in withdrawal limited operation. It was concluded that withdrawal limited operation was followed to have the premise of saving irrigation water, more instream flow water was able to be supplied from reservoirs with high magnification of paddy irrigation area to watershed area.

• 한국지구물리탐사학회:학술대회논문집
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• 2009.05a
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• pp.35-45
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• 2009

Reservoir Characterization (RC) using 3-D seismic attributes analysis can provide properties of the oil sand reservoirs, beyond seismic resolution. For example, distributions and temporal bed thicknesses of reservoirs could be characterized by Spectral Decomposition (SD) and additional seismic attributes such as wavelet classification. To extract physical properties of the reservoirs, we applied 3-D seismic attributes analysis to the oil sand reservoirs in McMurray formation, in BlackGold Oilsands Lease, Alberta Canada. Because of high viscosity of the bitumen, Enhanced Oil Recovery (EOR) technology will be necessarily applied to produce the bitumen in a steam chamber generated by Steam Assisted Gravity Drainage (SAGD). To optimize the application of SAGD, it is critical to identify the distributions and thicknesses of the channel sand reservoirs and shale barriers in the promising areas. By 3-D seismic attributes analysis, we could understand the expected paleo-channel and characteristics of the reservoirs. However, further seismic analysis (e.g., elastic impedance inversion and AVO inversion) as well as geological interpretations are still required to improve the resolution and quality of RC.

• Korean Journal of Ecology and Environment
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• v.40 no.2
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• pp.214-222
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• 2007

This study was conducted to assay the relationship between the characteristics of watershed and water quality, and to evaluate water quality characteristics of the classified types by TSI deviation analysis with the collected data from 490 reservoir. Relatively shallow depth (<5m) reservoirs out of selected 490 appeared to be eutrophic. The mean TP concentration in reservoirs with the PFA+UFA/watershed area of above 30% was ${\geq}0.1$ mg $L^{-1}$. The mean TN concentration in reservoirs with the PFA/watershed area of above 25% was ${\geq}2.6$ mg $L^{-1}$. Based on the TSI deviation analysis, water quality parameters in TYPE III reservoirs were in high concentration compared to other reservoirs types. Characteristics of Type III generally showed eutrophic, small DA/RA ratio, shallow depth, and large paddy field and upland field to watershed ratio compared to other types of reservoirs. Both water quality and morpho-physical parameters, Type I and II reservoirs were similar with the exceptions of BOD and chi. ${\alpha}$ concentration. Phosphorus in Type I reservoirs was not the primary limiting factor on algal growth, but significant decrease chl. ${\alpha}$ concentration with the increasing TN/TP indicated that phosphorus was the possible secondary limiting factor. Overall results indicated that type of land use, such as PFA and UFA area in watershed, was important parameters for the assessment of water quality characteristics, and phosphorus was limiting nutrient on algal growth in 490 reservoirs.

• Journal of Korean Society on Water Environment
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• v.21 no.1
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• pp.52-58
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• 2005

The assessment on characteristics of hydraulic behavior and water quality variations of underground reservoirs of buildings were studied. Firstly, it was thought that underground reservoir capacities($m^3$) of buildings should be not determinated by the uniform and same methods but be estimated on the basis of the dwelling areas on dominated households and their residential characteristics, because these characteristics influence significantly on actual water usages and patterns of buildings. Secondly, it was likely that the average reduction rate of residual chlorine in underground reservoirs were affected from the their capacities, because the average reduction rate of residual chlorine in underground reservoirs under $1,000m^3$ was 43 percent, on the other hand, that rate of underground reservoirs over $1,000m^3$ was 60 percent. Thirdly, through the field investigation, the retention time of drinking water in underground reservoirs were in the range from 0.3 day to 3.9 day. In addition to, the average reduction rate of residual chlorine were depended largely on the retention time of drinking water. When the retention time was under 24 hours, the average reduction rate of residual chlorine was 45 percent, and in case of over 24 hours, was 49 percent. Fourth, water level in underground reservoirs was averagely varied in the range from 0.1 m to 2.65 m at the height of underground reservoirs. If considered actual height of underground reservoirs, 37.6 percent of the height of underground reservoirs was only used. Consequently, the frequency of the inflow and outflow of drinking water in underground reservoir were very increased, and had an effect on the reduction of residual chlorine. Lastly, the investigations on hydraulic structure characteristics of underground reservoirs inside showed the locations of inflow and outflow of drinking water almost were in the opposite direction. And some buildings had several baffles in the middle. Nevertheless, their installations had no beneficial for the improvement of water quality.