We examined changes in water temperature in relation to air temperature in the two upper, two middle and lower reaches of the Han River basin, Republic of Korea. Air and water temperatures were monitored from 2020 to 2025, with analyses restricted to the May–October period of each year. T_W exhibited pronounced spatial variability, whereas T_A exhibited relatively low spatial variability. Hysteresis loops were analyzed separately for the warming (May–July) and cooling (August–October) phases using the air–water temperature relationship. Distinct phase-dependent patterns in air–water temperature differences were observed. Air–water temperature differences were greater in streams than in rivers, with values 4–5 °C higher during the warming phase and 4–6 °C lower during the cooling phase. Water temperature responses to air temperature showed phase-dependent spatial patterns, with regression slopes varying across stream and river systems and temperature elasticity decreasing from streams to rivers. Therefore, the results indicate that water temperature responses to air temperature vary both spatially and temporally, with sensitivity differing along the longitudinal gradient.

자원과학연구(Resources Science Research)

Erosion control dams (ECDs) in forested mountain streams are key pieces of infrastructure for disaster risk reduction, but they have also been reported to disturb the hydro-geomorphic balance of stream ecosystems. Open-type ECDs have increasingly been used to mitigate the loss of longitudinal connectivity caused by closed-type ECDs; however, quantitative comparisons between the two types remain scarce. We evaluated the presence of fish (Rhynchocypris oxycephalus) and amphibian (Glandirana emeljanovi) using logistic regression analysis in a forested mountain stream on Mt. Oseo, Republic of Korea, where closed- and open-type ECDs were installed in sequence. The best-fit models indicated different habitat preferences: R. oxycephalus responded to hydro-geomorphic parameters, whereas G. emeljanovi responded to riparian forest vegetation and soil parameters as well. Although six parameters varied significantly between the sections divided by the two types of ECDs, all observed values fell within the ranges previously reported for mountain streams in natural conditions. Bayesian Network Analysis further identified crown density, stream-bed slope, and number of step pools as high-level parameters that can be regulated through erosion control works, including engineering and forestry techniques. These findings link the presence of both species to stream conditions and are translated into an ecosystem management framework, filling a knowledge gap where comparable studies are scarce.