• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.1B
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• pp.11-22
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• 2009

Long-term rainfall-runoff modeling is a key element in the Earth's hydrological cycle, and associated with many different aspects such as dam design, drought management, river management flow, reservoir management for water supply, water right permission or coordinate, water quality prediction. In this regard, hydrologists have used the hydrologic models for design criteria, water resources assessment, planning and management as a main tool. Most of rainfall-runoff studies, however, were not carefully performed in terms of considering reservoir effects. In particular, the downstream where is severely affected by reservoir was poorly dealt in modeling rainfall-runoff process. Moreover, the effects can considerably affect overall the rainfallrunoff process. An objective of this study, thus, is to evaluate the impact of reservoir operation on rainfall-runoff process. The proposed approach is applied to Anseong watershed, where is in a mixed rural/urban setting of the area and in Korea, and has been experienced by flood damage due to heavy rainfall. It has been greatly paid attention to the agricultural reservoirs in terms of flood protection in Korea. To further investigate the reservoir effects, a comprehensive assessment for the results are discussed. Results of simulations that included reservoir in the model showed the effect of storage appeared in spring and autumn when rainfall was not concentrated. In periods of heavy rainfall, however, downstream runoff increased in simulations that do not consider reservoir factor. Flow duration curve showed that changes in streamflow depending upon the presence or absence of reservoir factor were particularly noticeable in ninety-five day flow and low flow.

• Korean Journal of Remote Sensing
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• v.40 no.4
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• pp.363-375
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• 2024

Waterbody change detection using satellite images has recently been carried out in various regions in South Korea, utilizing multiple types of sensors. This study utilizes optical satellite images from Landsat and Sentinel-2 based on Google Earth Engine (GEE) to analyze long-term surface water area changes in four monitored small and medium-sized water supply dams and agricultural reservoirs in South Korea. The analysis covers 19 years for the water supply dams and 27 years for the agricultural reservoirs. By employing image analysis methods such as normalized difference water index, Canny Edge Detection, and Otsu'sthresholding for waterbody detection, the study reliably extracted water surface areas, allowing for clear annual changes in waterbodies to be observed. When comparing the time series data of surface water areas derived from satellite images to actual measured water levels, a high correlation coefficient above 0.8 was found for the water supply dams. However, the agricultural reservoirs showed a lower correlation, between 0.5 and 0.7, attributed to the characteristics of agricultural reservoir management and the inadequacy of comparative data rather than the satellite image analysis itself. The analysis also revealed several inconsistencies in the results for smaller reservoirs, indicating the need for further studies on these reservoirs. The changes in surface water area, calculated using GEE, provide valuable spatial information on waterbody changes across the entire watershed, which cannot be identified solely by measuring water levels. This highlights the usefulness of efficiently processing extensive long-term satellite imagery data. Based on these findings, it is expected that future research could apply this method to a larger number of dam reservoirs with varying sizes,shapes, and monitoring statuses, potentially yielding additional insights into different reservoir groups.

• Journal of the Korean Institute of Traditional Landscape Architecture
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• v.39 no.4
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• pp.50-65
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• 2021

In this study, the water flow system by measuring the flow-way type and distance of flow path that composes the Gugok through literature survey, field survey, and map work on Gugok gardens in Korea whose existence has been confirmed, while investigating and analyzing watersheds, river orders, and river grades. It was intended to reveal the watershed distribution and stream morphological characteristics of the Gugok gardens and to use them as basic data for future enjoyment and conservation of the Gugok gardens. The conclusion of the study is as follows. First, Of the 93 Gugok gardens that have been confirmed to exist, it was found that 11 places(11.8%) were found to have a descending(top-down) type of Gugok that develops while descending along a stream. Second, As a result of analysis of the length of the flow path for each valley, Okryudonggugok(玉流洞九曲, Namsan-gugok) in Gimcheon, Gyeongsangbuk-do was found to have the shortest length of 0.44km among the surveyed valleys, while the flow distance of Muheulgugok(武屹九曲) located in Seongju-gun and Gimcheon-si, Gyeongsangbuk-do was 31.1km, showing the longest flowing distance. The average flow path length of the Gugok Garden in Korea was 6.24km, and the standard deviation was 4.63km, indicating that the deviation between the 'curved type'e and the 'valley type' was severe. In addition, 14(15.1%) Gugok gardens were found to be partially submerged due to dam construction. Third, As a result of analyzing the waters area where Gugok garden is located, the number of Nakdong river basins was much higher at 52 sites(55.9%), followed by the Hangang river basin at 27 sites(28.7%), the Geum river basin at 9 sites(9.7%), and the Yeongsan river and Seomjin river basins at 5(5.4%). Fourth, All Gugok gardens located in the Han river region were classified as the Han river system, and the Gugok garden located on the Nakdong river was classified as the main Nakdong river system, except for 7 places including 5 places in the Nakdong Gangnam Sea water system and 2 places in the Nakdong Gangdong sea water system. As a result of synthesizing the river order of the flow path where Gugok garden is located, Gugok, which uses the main stream as the base of Gugok, is 3 places in the Hangang water system, 5 places in the Nakdong river system, 2 places in the Geumgang water system, and 1 place in the Yeongsangam/Seomjin river system. A total of 11 locations(11.5%) were found, including 36 locations(38.2%) in the first branch, 29 locations(31.2%) in the second branch, and 16 locations(17.0%) in the third branch. And Gugok garden, located on the 4th tributary, was found to be Taehwa Five-gok(太華五曲) set in Yonghwacheon Stream in Cheorwon in the Han river system, and Hoenggyegok(橫溪九曲) in Yeongcheon Hoenggye Stream in the Nakdong river system. Fifth, As a result of the river grade analysis of the rivers located in the Gugok garden Forest, the grades of the rivers located in the Gugok garden were 13 national rivers(14.0%), 7 local first-class rivers(7.5%), and 74 local second-class rivers(78.5%) was shown.