• Ecology and Resilient Infrastructure
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• v.9 no.1
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• pp.24-35
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• 2022

For water quality management, it is necessary to continuously improve the forecasting by analyzing the past water quality, and a Data-driven model is emerging as an alternative. Because the Data-driven model is built based on a wide range of data, it is essential to apply the correlation analysis method for the combination of input variables to obtain more reliable results. In this study, the Gamma Test was applied as a preceding step to build a faster and more accurate data-driven water quality prediction model. First, a physical-based model (HSPF, EFDC) was operated to produce daily water quality reflecting the complexity of the watershed according to various hydrological conditions for Paldang Dam. The Gamma Test was performed on the water quality at the water quality prediction site (Paldangdam2) and major rivers flowing into the Paldang Dam, and the method of selecting the optimal input data combination was presented through the analysis results (Gamma, Gradient, Standar Error, V-Ratio). As a result of the study, the selection criteria for a more efficient combination of input data that can save time by omitting trial and error when building a data-driven model are presented.

• Journal of Korea Water Resources Association
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• v.55 no.11
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• pp.979-989
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• 2022

In hydrological surveys, observation through representative location is essential due to temporal and spatial limitations and constraints. Regarding the use of hydrological data and the accuracy of the data, there are still insufficient observatories to be used in a specific watershed. In addition, since there is virtually no standard for the location of the current evapotranspiration, this study proposes a method for determining the location of the evapotranspiration. To determining the location of evapotranspiration, a grid is selected in consideration of the operating range of the Flux Tower using the eddy covariance measurement method, which is mainly used to measure evapotranspiration. The grid of representative location was calculated using the factors affecting evapotranspiration and satellite data of evapotranspiration. The grid of representative location was classified as good, fair, and poor. As a result, the number of good grids calculated was 54. It is judged that the classification of the grid has been achieved regarding topography and land use as a characteristic that appeared in the classification of the grid. In particular, in the case of elevation or city area, there was a large deviation, and the calculated good grid was judged to be a group between the two distributions.

• Journal of Korea Water Resources Association
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• v.55 no.11
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• pp.877-886
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• 2022

This study was carried out to analyze how the flow and water quality of the Sangsa Lake (juam control basin) change according to future climate change and what countermeasures are needed. Aquatic Ecosystem Model) was used in conjunction. As climate change scenarios, RCP (Representative Concentration Pathways) 4.5 and RCP 8.5 scenarios of AR5 (5th Assessment Report) according to the Intergovernmental Panel on Climate Change (IPCC) were used. For the climate change scenario, detailed data on the Sangsa Lake basin were used by the Korea Meteorological Administration, and after being evaluated as a correction and verification process for the 10-year period from 2012 to 2021, the present, 2025-2036, 2045- The summer period from June to August and the winter period from December to February were analyzed separately for each year by dividing it into 2056 and 2075-2086. RCP 8.5 was higher than RCP 4.5 as an arithmetic mean for the flow rate of the watershed of the superior lake for the entire simulation period, and TN and TP also showed a tendency to be higher at RCP 4.5. However, in RCP 8.5, the outflow of pollutants decreased during the dry season and the outflow of pollutants increased during the summer, indicating that the annual pollutant outflow was concentrated during the flood season, and it is analyzed that countermeasures are needed.

• Korean Journal of Ecology and Environment
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• v.55 no.4
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• pp.294-304
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• 2022

This study carried out from March 2021 to October 2021 in the upper part (St. 1) and middle part (St. 2) section of Yongsu stream, a branch of the Geum river, using PIT telemetry to understand the movement patterns and habitat characteristics of Odontobutis interrupta, a Korean endemic species. O. interrupta collection was used kick net (5×5 mm) and fish trap (5×5 mm). After collecting fish, PIT tag insertion was performed immediately in the site. Reader (HPR Plus Reader, biomark, USA) and portable Antenna (BP Plus Portable Antenna, biomark, USA) were used for detection of fish to monitoring the tagged O. interrupta. As a result of PIT telemetry applied to 70 individuals, mean movement distance was 36.5 (SE, ±6.6) m. There was a significant difference between total length and movement distance (P≤0.05). O. interrupta was mainly identified in average water depth, 36.2±1.9 cm, average water velocity, 0.03±0.07 m s^-1 and average distance from watershed, 4.4±0.3 m. Extent of rock used for habitat was varied from 32 to 4,000 cm². There was no statistical difference between the area of the first selected rock and the area of the after selected rock (P>0.05). but there was significant difference between total length and the area of the rock except for detection before 24 hours (P<0.01). Therefore, to restore the habitat, it is considered necessary to create various substrate structures by providing various habitat environments (water depth, flow rate, stone, etc.) for each individual size.

• Journal of Korean Society of Forest Science
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• v.112 no.3
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• pp.340-351
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• 2023

Landslides are major natural geological hazards that cause enormous property damage and human casualties annually. The vulnerability of mountainous areas to landslides is further exacerbated by the impacts of climate change. Soil depth is a crucial parameter in landslide and debris flow analysis, and plays an important role in the evaluation of watershed hydrological processes that affect slope stability. An accurate method of estimating soil depth is to directly investigate the soil strata in the field. However, this requires significant amounts of time and money; thus, numerous models for predicting soil depth have been proposed. However, they still have limitations in terms of practicality and accuracy. In this study, 71 seismic survey results were collected from domestic mountainous areas to estimate soil depth on hill slopes. Soil depth was estimated on the basis of a shear wave velocity of 700 m/s, and a database was established for slope angle, elevation, and soil depth. Consequently, the statistical characteristics of soil depth were analyzed, and the correlations between slope angle and soil depth, and between elevation and soil depth were investigated. Moreover, various soil depth prediction models based on slope angle were investigated, and corrected linear and exponential soil depth prediction models were proposed.

• Ecology and Resilient Infrastructure
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• v.10 no.3
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• pp.73-84
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• 2023

The objective of this study was to evaluate biodiversity and natural habitat environment of freshwater ecosystem. Our aim was therefore to produce a set of biodiversity and habitat indicators based on multi-parameters of water quality and biodiversity by analyzing the characteristics of the results by indicators. We selected four indicators a) anthropogenic disturbance, b) habitat diversity, c) biodiversity, d) ecosystem structure. The fishes cohabiting with Brachymystax lenok tsinlingensis were Rhynchocypris kumgangensis and Zacco koreanus. As a result of the anthropogenic disturbance evaluation, it was analyzed that vegetation embankment showed a more stable environment in the tributary than the main stream, and other disturbance was not confirmed As a result of the habitat diversity evaluation, it was analyzed that habitat evaluation index showed a high score of 200 more on average, showing an optimal habitat condition. As a result of the biodiversity evaluation, it was analyzed as a clean habitat condition with a high proportion of sensitive species, abundant dissolved oxygen, and little pollutants. As a results of the ecosystem structure, the ecological health condition metrics and appearance of endangered species showed large score deviation, but it was analyzed that the stream ecosystem health was generally excellent. There was a slight correlation between the habitat environment and the results of the nature habitat evaluation according to the appearance of the B. lenok tsinlingensis.

• Journal of The Geomorphological Association of Korea
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• v.17 no.2
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• pp.63-76
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• 2010

The Jangdo wetland is located on a very gentle slope of the mountain area in Daejangdo island, Shinan-gun, Korea, in which the area of the watershed is estimated at 147,000 m². The wetland has been regarded as a peat bog without any sedimentological evidence. This study was conducted to analyze the geomorphological and sedimentological characteristics of the wetland. The geographic information system (GIS) was used to analyze the drainage system, and field surveys were conducted to measure the range and depth of wetland deposits. The grain size analysis, organic matter determination, elements analysis and radiocarbon dating were performed on samples from the wetland. As a result, the wetland deposits were about 30 cm deep on average, the mean grain sizes ranged from 50 to 500 μm, and the average C/N ratio was 11.5. The portion of organic matter it contained was only 5~26%, which did not satisfy the peat standards. The radiocarbon ages from the wetland deposits range 180±50 ¹⁴C yr BP to modern, which indicated that natural and anthropogenic interferences including agricultural activities have continuously happened. We conclude that the Jangdo wetland is still in its infancy, not a steady state, so that it could be very sensitive to a small disturbance.

• Journal of Korea Water Resources Association
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• v.56 no.3
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• pp.211-224
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• 2023

In this study, a soil moisture estimation was performed using the Water Cloud Model (WCM), a backscatter model that considers vegetation based on SAR (Synthetic Aperture Radar). Sentinel-1 SAR and Sentinel-2 MSI (Multi-Spectral Instrument) images of a 40 × 50 km² area including the Yongdam Dam watershed of the Geum River were collected for this study. As vegetation descriptor of WCM, Sentinel-1 based vegetation index RVI (Radar Vegetation Index), depolarization ratio (DR), and Sentinel-2 based NDVI (Normalized Difference Vegetation Index) were used, respectively. Forward modeling of WCM was performed by 3 groups, which were divided by the characteristics between backscattering coefficient and soil moisture. The clearer the linear relationship between soil moisture and the backscattering coefficient, the higher the simulation performance. To estimate the soil moisture, the simulated backscattering coefficient was inverted. The simulation performance was proportional to the forward modeling result. The WCM simulation error showed an increasing pattern from about -12dB based on the observed backscattering coefficient.

• Journal of Korea Water Resources Association
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• v.56 no.6
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• pp.393-402
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• 2023

Drought, which has been increasing in frequency and magnitude due to recent abnormal weather events, poses severe challenges in various sectors. To address this issue, it is important to develop technologies for drought monitoring, forecasting, and response in order to implement effective measures and safeguard the ecological health of aquatic systems during water scarcity caused by drought. This study aimed to predict water quality fluctuations during drought periods by integrating the watershed model HSPF and the water quality model QUAL-MEV. The researchers examined the SPI and RCP 4.5 scenarios, and analyzed water quality changes based on flow rates by simulating them using the HSPF and QUAL-MEV models. The study found a strong correlation between water flow and water quality during the low flow. However, the relationship between precipitation and water quality was deemed insignificant. Moreover, the flow rate and SPI6 exhibited different trends. It was observed that the relationship with the mid- to long-term drought index was not significant when predicting changes in water quality influenced by drought. Therefore, to accurately assess the impact of drought on water quality, it is necessary to employ a short-term drought index and develop an evaluation method that considers fluctuations in flow.

• Korean Journal of Environmental Biology
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• v.40 no.1
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• pp.1-10
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• 2022

Global warming has a major impact on the Earth's precipitation and temperature fluctuations, and significantly affects the habitats and biodiversity of many species. Although the number of alien plants newly introduced in South Korea has recently increased due to the increasing frequency of international exchanges and climate change, studies on how climate change affects the distribution of these alien plants are lacking. This study predicts changes in the distribution of suitable habitats according to RCPs climate change scenarios using the current distribution of the invasive alien plant Conyza sumatrensis and bioclimatic variables. C. sumatrensis has a limited distribution in the southern part of South Korea. Isothermality (bio03), the max temperature of the warmest month (bio05), and the mean temperature of the driest quarter (bio09) were found to influence the distribution of C. sumatrensis. In the future, the suitable habitat for C. sumatrensis is projected to increase under RCP 4.5 and RCP 8.5 climate change scenarios. Changes in the distribution of alien plants can have a significant impact on the survival of native plants and cause ecosystem disturbance. Therefore, studies on changing distribution of invasive species according to climate change scenarios can provide useful information required to plan conservation strategies and restoration plans for various ecosystems.