How Land Use and Hydrological Characteristics Impact Stream Conditions in Impaired Ecosystems

Anthropogenic influence has altered watershed environments and hydrological processes, leading to increased occurrences of impaired streams and negative impacts on benthic invertebrates. While individual environmental factors affecting benthic macroinvertebrates have been studied, the cascading effects of land use change and hydrological alterations remain unclear. This study employed structural equation modeling (SEM) to analyze the interactions among land use proportion, hydrological characteristics, substrate composition, and water quality and their influence on benthic macroinvertebrate communities in impaired streams upstream of the Paldang Dam in the Han River Basin, South Korea. Analysis of data from 24 streams surveyed between 2018 and 2022—3 or 6 streams per year—under the Impaired Stream Diagnosis Program indicated that urban and agricultural land cover, low substrate diversity, high pollutant concentrations, and altered flow conditions (low velocity and discharge) were associated with decreased pollution-sensitive Ephemeroptera, Plecoptera, and Trichoptera (EPT) taxa and increased pollution-tolerant and collector–gatherer taxa. These findings highlight the role of land use-driven hydrological changes in stream ecosystem degradation and underscore the need for targeted restoration strategies, such as riparian buffer zones, substrate enhancement, and hydrological flow restoration, to mitigate these impacts and improve benthic macroinvertebrate habitats.