• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.4
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• pp.287-294
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• 2021

A Python-based LSTM model was constructed using a Tensorflow backend to estimate the amount of outflow during floods in the Gokgyo-cheon basin flowing into the Sapgyo Lake. To understand the effects of the length of input data used for learning, i.e., the sequence length, on the performance of the model, the model was implemented by increasing the sequence length to three, five, and seven hours. Consequently, when the sequence length was three hours, the prediction performance was excellent over the entire period. As a result of predicting three extreme rainfall events in the model verification, it was confirmed that an average NSE of 0.96 or higher was obtained for one hour in the leading time, and the accuracy decreased gradually for more than two hours in the leading time. In conclusion, the flood level at the Gangcheong station of Gokgyo-cheon can be predicted with high accuracy if the prediction is performed for one hour of leading time with a sequence length of three hours.

• Journal of Korean Society of Environmental Engineers
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• v.33 no.10
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• pp.739-747
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• 2011

The major 81 tributaries in Chungcheongnam-do were monitored for flowrate and water quality in order to understand the characteristics of the watershed and to select the tributary catchment for improving water quality. The value of flowrate in the tributaries at Nonsancheon catchment at the Geum-River watershed and Gokgyocheon, Muhancheon, Sapgyocheon at the Sapgyo-Reservoir watershed, which is located in the southern and northern area in Chungcheongnam-do, was relatively greater than the other watersheds. The concentration of water pollutants regardless of water quality parameters in Nonsancheon catchment at the Geum-River watershed, Gokgyocheon catchment at the Sapgyo-Reservoir watershed and the Anseongcheon watershed, which have a dense source of pollution, were higher than the other watersheds. However, 64 percent of the tributaries at the Geum-River watershed, 45 percent of tributaries at the Sapgyo-Reservoir watershed, 26 percent of tributaries at the Geum-River watershed all satisfied the Class II regulations in the Framework Act on Environment Policy, but all of the tributaries located in the Anseongcheon watershed exceeded the Class II regulations. Therefore, the policy for improving the water quality of the tributary in Chungcheongnam-do should be established in the following order: Anseongcheon, Seohae, Sapgyo-Reservoir watersheds. Consequently, the tributary catchment for improving water quality, which has a large flowrate and a high concentration of water pollutants, was selected at Ganggyeongcheon, Geumcheon, Nonsancheon, Seokseongcheon, Seungcheoncheon, Jeongancheon, Jeungsancheon (so far Geum-River watershed), Gokgyocheon, Namwoncheon, Maegokcheon, Muhancheon, Sapgyocheon Oncheoncheon, Cheonancheon (so far Sapgyo-Reservoir watershed), Gwangcheoncheon, Dangjincheon, Daecheoncheon, Dodangcheon, Waryongcheon, Cheongjicheon, Pangyocheon, Heungincheon (so far Seohae watershed), Dunpocheon, Seonghwancheon, Ipjangcheon (so far Anseongcheon watershed). The plans as installation of environmental facilities to reduce the source of pollution for improving the water quality of these tributary catchments should be urgently established and implemented.

• Journal of The Geomorphological Association of Korea
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• v.20 no.1
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• pp.11-20
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• 2013

The pollen analysis was performed targeting the valley plain alluvium of Jangjae-ri, Asan area in order to clarify the climate and vegetation environment of the Last glacial maximum and the Late glacial in terms of Gokgyo River Watershed In Asan-City, Korea. The sample collection point gets included in the current deciduous broadleaf forest zone (south cool temperate zone). The results are as follows. (1) The vegetation environment of about 19,300-14,100yrB.P. at the investigation area is mainly classified into YJ-I period and YJ-II period while YJ-Ia period is classified once again into YJ-Ia period and YJ-Ib period. YJ-Ia period (19,300-17,500yrB.P.) is correlated with the Last Glacial Maximum while the vegetation at the time has relatively a little wide distribution area of grassland compared to the forest and the forest vegetation of this time period is the mixed conifer and deciduous broad-leaved forest. YJ-Ib period (15,400-14,750yrB.P.) is correlated with the Late glacial (or the Last Glacial Maximum) and the distribution area of grassland became wider compared to the forest. While the forest vegetation of this time period is the mixed conifer and deciduous broad-leaved forest, a difference exists in terms of the dominant tree species. YJ-II period (about 14,650-14,100yrB.P.) is correlated with the Last glacial while the distribution area of grassland became even wider than the forest compared to the YJ-Ib in case of the vegetation at the time and the forest vegetation of this time period is the coniferous forest. (2) Both YJ-I period and YJ-II period were relatively cold and dry compared the End of Late Glacial (about 12,000-10,000yrB.P.)~Early Holocene (10,000-8,500yrB.P.), Also, YJ-II period was relatively colder than the YJ-I period and the YJ-Ib period was relatively more humid than the YJ-Ia period.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.39 no.4
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• pp.235-243
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• 2021

River surveying is conducted to acquire basic geographic data for river master plans and various river maintenance, and it is also used to predict changes after river maintenance construction. ABL (Airborne Bathymetric LiDAR) system is a cutting-edge surveying technology that can simultaneously observe the water surface and river bed using a green laser, and has many advantages in river surveying. In order to use the ABL data for river surveying, it is prerequisite step to segment and extract the water surface and river bed points from the original point cloud data. In this study, point cloud segmentation was performed by applying the ground filtering technique, ATIN (Adaptive Triangular Irregular Network) to the ABL data and then, the water surface and riverbed point clouds were extracted sequentially. In the Gokgyocheon river area, Chungcheongnam-do, the experiment was conducted with the dataset obtained using the Leica Chiroptera 4X sensor. As a result of the study, the overall classification accuracy for the water surface and riverbed was 88.8%, and the Kappa coefficient was 0.825, confirming that the ABL data can be effectively used for river surveying.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.2
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• pp.404-411
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• 2019

In this study, the HEC-HMS was applied to determine rainfall-runoff processes for the Gokgyuchun basin. Several sub-basins have large-scale reservoirs for agricultural needs and they store large amounts of initial runoff. Three infiltration methods were implemented to reflect the effect of initial loss by reservoirs: 'SCS-CN'(Scheme I), 'SCS-CN' with simple surface method(Scheme II), and 'Initial and Constant rate'(Scheme III). Modeling processes include incorporating three different methods for loss due to infiltration, Clark's UH model for transformation, exponential recession model for baseflow, and Muskingum model for channel routing. The parameters were calibrated using an optimization technique with trial and error method. Performance measures, such as NSE, RAR, and PBIAS, were adopted to aid in the calibration processes. The model performance for those methods was evaluated at Gangcheong station, which is the outlet of study site. Good accuracy in predicting runoff volume and peak flow, and peak time was obtained using the Scheme II and III, considering the initial loss, whereas Scheme I showed low reliability for storms. Scheme III did not show good matches between observed and simulated values for storms with multi peaks. Conclusively, Scheme II provided better results for both single and multi-peak storms. The results of this study can provide a useful tool for decision makers to determine master plans for regional flood control management.

• Journal of Environmental Impact Assessment
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• v.9 no.4
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• pp.339-348
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• 2000

This study was conducted to investigate the distribution pattern of plants on the streamside of Goggyochun, and to survey the distribution of heavy metal-contaminated soils and plants. A total of 11 survey sites were selected along the Goggyochun during the period of between June and September 1999. The wet land plants were composed of 44 species. The most frequently occurring species in the study sites were Rumex crispus, Persicaria hydropiper, Cyperus amuricus and Setaria viridis, and among them the Humulus japonicus, Erigeron canadensis and Phragnites communis species were dominants of the community. Analysis of soil properties showed that organic matter and clay contents were higher in the upstream region while sand content was higher in the downstream region. The pH and the organic matter contents of soils were at range of 6.70-9.94 and 2.39-15.16% respectively. The average contents of Pb and Cd in soils were 11.96mg/kg and 1.64mg/kg respectively, and these values were higher as compared with those of ordinary soil in Korea. The average contents of Zn and Pb in Persicaria hydropiper were 8.30mg/kg and 7.38mg/kg respectively, and these values were higher than other plants. The distribution of heavy metals in plants varied in accordance with the species regardless of the sites.

• Journal of Korea Water Resources Association
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• v.46 no.10
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• pp.1005-1016
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• 2013

The objective of this study was to evaluate spatio-temporal water shortage distribution in the Sapgyo catchment considering both permitted and non-permitted water rights obtained from the total water right survey conducted in 2010. The results showed that the agricultural water accounted for 98% of the total water uses with 83% being the non-permitted agricultural water uses. During the 11-year (2001~2011) simulation period, water shortage was shown only in the upper Gokgyo stream sub-catchment with the highest water stress from April to May in 2009, particularly because of the large demand for rice cultivation associated with low precipitation. As water shortage was not expected to happen when the permitted water rights were not considered, it was concluded that a proper management of non-permitted water rights would be urgent.

• Journal of Korea Water Resources Association
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• v.46 no.6
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• pp.667-681
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• 2013

In this study, monthly and seasonal dissolved oxygen trends of 19 water quality measurement stations in Sapgyo stream watershed were analyzed using monthly dissolved oxygen (DO) data measured for 16 years (1995~2010). Mann-Kendall trend test and Sen's slope estimator were carried out for trend analysis. Furthermore, Sapgyo stream watershed was divided into four different sections (Sapgyo stream, Muhan stream, Gykgyo stream, and Sapgyo lake) and chi-square test of homogeneity for DO trend was carried out for four different sections. The study results indicated that most of water quality measurement stations showed increasing or non-significant trend of DO on a monthly and seasonal basis. The chi-square test of homogeneity for each water quality measurement station showed the statistical homogeneity in seasonal DO trend; however, the test results showed the statistical non-homogeneity in monthly DO trend for the stations located in the reservoir. Overall, the dissolved oxygen trend in each water quality measurement station showed different patterns depending on the location of each station and season.

• Korean Journal of Ecology and Environment
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• v.34 no.1 s.93
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• pp.62-69
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• 2001

This study was investigated discharge and water quality for rainy days at the inflow streams (Gog-Kyo, Mu-Han, Sap-Kyo and Nam-Won) into Lake Sap-Kyo from June to November of 1999. The eventual aim of this study was to improve the water quality of Lake Sap-Kyo. Therefore, in order to reduce inflow pollutants loading into Lake Sap-Kyo, we investigated characteristics of stormwater runoff and estimated pollutant loading for the rainy season. The results of that Sap-Kyo stream is $5.75\;m^3/sec$ flow and influences water quantity of Lake Sap-Kyo greatly during the dry weather. Gog-Kyo stream influence to quantity of Lake Sap-Kyo greatly for the rainy days. Gog-Kyo stream and Sap-Kyo stream are $12.13\;m^3/sec$ and $8.49\;m^3/sec$, respectively. The reason is that the watershed area of Gog-Kyo stream is larger than other streams. When we prepare to plan management to improve the water quality of Lake Sap-Kyo, we have to consider that runoff characteristics by land use. Among the annual total pollutants loading inflow Lake Sap-Kyo, the ratio of non-point pollutants loading estimated that SS, BOD, T-N and T-P are 62%, 43%, 41% and 27%, respectively. Therefore, in order to improve water quality of Lake Sap-Kyo, we have to reduce non-point pollutants loading.

• Korean Journal of Environmental Biology
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• v.41 no.2
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• pp.101-108
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• 2023

Recently, in relation to climate change, many studies have been conducted to predict the potential habitat area and distribution range of tilapia and the suitability of habitat for each species. Most tilapia are tropical fish that cannot survive at water temperatures below 10 to 12℃, although some tilapia can survive at 6 to 8℃. This study predicted habitable areas and the possibility of spreading of habitat ranges of tilapia (Oreochromis niloticus and Oreochromis aureus) known to inhabit domestic streams. Due to climate change, it was found that habitats in the Geum River, Mangyeong River, Dongjin River, Seomjin River, Taehwa River, Hyeongsan River, and the flowing in East Sea were possible by 2050. In addition, it was confirmed that tilapia could inhabit the preferred lentic ecosystem such as Tamjin Lake, Naju Lake, Juam Lake, Sangsa Lake, Jinyang Lake, Junam Reservoir, and Hoedong Reservoir. In particular, in the case of tilapia, which lives in tributaries of the Geumho River, Dalseo Stream, and the Nakdong River, its range of habitat is expected to expand to the middle and lower of the Nakdong River system. Therefore, it is judged that it is necessary to prepare physical and institutional management measures to prevent the spread of the local population where tilapia currently inhabits and to prevent introduction to new habitats.