In the Gucheon stream of Deogyusan National Park, a survey was conducted at three sites (six sites in total) in 2018 and 2021. A total of benthic macroinvertebrates of 107 taxa 46 families 13 orders in 6 classes of 5 phyla were found. According to the analysis of the appearance by year, a total of 87 species were surveyed in 2018, and a total of 89 species were surveyed in 2021. As a results to the functional feeding group analysis, Gathering-Collector (GC) accounted for a high species share (2018: 29.89%, 2021: 25.84%). In the functional habitat group analysis, Clinger (CL) accounted for a high species share (2018: 56.32%, 2021: 57.30%). Average annual community indices analysis, DI 0.38(±0.05), H′ 3.48(±0.19), R′ 3.23(±0.41), and J′ 0.85(±0.04) in 2018, and DI 0.55(±0.09), H′ 2.98(±0.31), R′ 2.91(±0.65), and J′ 0.70(±0.05) in 2021. As a results of the benthic macroinvertebrates index (BMI) analysis, indicating that all sites were classified as "very good," with average BMI values of 95.24(±2.84) in 2018 and 96.99(±1.13) in 2021.

Water chemistry and fish community, based on fish compositions and ecological characteristics(trophic/tolerance guilds and condition factor), were compared in Gucheon Reservoir(GcR) and Yeoncho Reservoir(YcR). Chemical parameters of water quality such as BOD, COD, nutrient(N, P) and suspended solids indicated that water quality was better in the YcR than GcR, and the temporal variability in seasonal and interannual patterns were greater in the YcR. The greater variability was mainly attributed to intense dilutions of reservoir water by Asian monsoon rain during July–August. Fish guild analysis indicated that species diversity was higher in the GcR than the YcR, and that the proportion of tolerant and omnivore species were greater in the YcR. Regression analysis of body weight-total length showed that the regression coefficient(b value) was lower in the GcR(2.15 ~ 2.40) than the YcR(2.59 ~ 3.14). Condition factor(K) of fish against the total length showed negative slope of Zacco temminckii, Carassius auratus, Pseudorasbora parva and Rhinogobius brunneus population in the GcR, and a positive slope of Carassius auratus and Rhinogobius brunneus population in YcR. Overall, our data suggest that the growth of the fish populations, based on the length-weight relations and condition factor, reflected the trophic regime of nutrients and organic matter.