The dependences of the filtration and respiration rates of a freshwater bivalve in Lake Biwa, which was inferred to be Corbicula leana, on water temperature and dissolved oxygen (DO) concentration were determined through cultivation experiments and literature survey to evaluate its habitable condition. The filtration rate of the bivalve with a shell length of 14.9 ± 1.2 mm depended on water temperature and DO concentration. The effect of water temperature on filtration rate was modeled as an exponential function with a high-temperature inhibition and the optimal temperature was evaluated to be 20.8 ℃. The filtration rate reached a plateau at a DO concentration above 4 mg L⁻¹ and decreased at a DO concentration of 2.6 mg L⁻¹. When the feed concentration at the bottom of the southern basin of Lake Biwa was assumed to be 3 mg-C L⁻¹, the growable temperature range of the bivalve was estimated to be 12.1–26.6 ℃ at the DO concentration ≥ 4 mg L⁻¹. The annual growth rate of the bivalve was estimated to decrease by 0.005–0.01 g-C y⁻¹ indiv.⁻¹ with a 1 ℃ increase in water temperature. Thus, lake warming was considered to negatively affect the bivalve population in Lake Biwa.

For use in countermeasures to chemical spill accidents in river basins for national and local governments, we developed quick reference tables for flowing prediction of chemical concentrations. Accident points were set up to reflect the differences in catchment area and gradient in three river systems of various basin sizes, and simulations were conducted for sunny, rainy, and severe rainfall conditions using the AIST–SHANEL model with a 1-minute time resolution. Using these simulation results, we made quick reference tables of the concentrations of substances relative to the distance and time from the accident. All the tables were summarized in terms of catchment area and gradient and indicated that the chemical flow downstream time tends to be shorter when the gradient is larger and the peak concentration of a chemical substance tends to be lower when the catchment area is larger owing to dilution effects. We will develop quick reference tables of chemical concentrations for more river systems and chemical substances with different physical properties, which will enable us to devise more efficient countermeasures to chemical spill accidents occurring in any river system in Japan.