Abstract
Cross sectional profile, hyporheic flow velocity, dissolved oxygen, temperature of hyporheic flow and spawning redds distribution were surveyed in 3 sections which have different characteristics, such as thin gravel layer section, transiting gravel thickness (declining toward downstream) layer section and thick gravel layer section. The results show that hyporheic flow velocity and dissolved oxygen were high, and temperature of hyporheic flow was low as river water, on the thin gravel layer section. The thick gravel layer section has different characteristics from thin gravel layer section. The section included points standing out in about half amount of dissolved oxygen from other points and about 2 degrees celsius higher temperature than river water.Thus, it was considered that long residence time hyporheic flow mixed on the thick gravel layer section. Similar trend of hyporheic flow temperature was confirmed on the transiting gravel thickness layer section. Few spawning redds were confirmed on the thin gravel layer section. On the other hand, many spawning redds were confirmed on the thick gravel layer section and the transiting gravel thickness layer section. Thus, it was considered that contiguous thick gravel layer condition contributes to spawning environment.
