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Title |
Analysis of the Impact of Stream Flow on the Exceedance Probability of Extreme Stream Water Temperature using Joint Probability Model
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Authors |
손예지(Yeji Shon) ; 이채림(Chaelim Lee) ; 김상단(Sangdan Kim) |
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DOI |
https://doi.org/10.15681/KSWE.2026.42.1.57 |
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Keywords |
Conditional exceedance probability; Copula model; Extreme river temperature; Low flow; Risk assessment |
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Abstract |
Turbidity, mainly caused by suspended sediments (SS), significantly impacts river ecosystems by reducing populations of sensitive taxa while promoting tolerant species. Traditional biological indices, such as species richness, the Benthic Macroinvertebrates Index (BMI), and the Benthic Macroinvertebrates Streambed Index (BMSI), may not adequately capture the cumulative and long-term effects of turbidity. To address this gap, we created the Turbidity Sensitivity Index for Benthic Macroinvertebrates (TSI-BM) specifically for the upper Soyang River Dam in the North Han River basin. We defined turbidity exposure as the cumulative SS concentration over six months, reflecting long-term stress rather than short-term variations. We analyzed correlations between cumulative exposure and 255 taxa within the groups Ephemeroptera, Plecoptera, and Trichoptera (EPT) to classify species into four sensitivity categories. Sensitive groups (A and B) were weighted to calculate TSI-BM, which represents the proportion of sensitive taxa scores within a community. TSI-BM demonstrated strong and consistent negative correlations with turbidity exposure (Spearman's ρ ? ?0.46, p < 0.001), outperforming conventional indices. It effectively captured spatial variations among sites and seasonal differences, proving to be a robust diagnostic tool. These findings suggest that TSI-BM integrates species-specific sensitivity with cumulative stressor exposure, offering a stressor-specific and ecologically relevant metric for turbidity assessment. Beyond enhancing the ecological evaluation of sediment stress, TSI-BM provides a practical framework for biomonitoring and managing river ecosystems amid changing hydrological conditions and land-use pressures.
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