We examined the usage of photographs for observation of river water quality because photographs are convenient to record river conditions.

The difference of visual impressions was investigated with photographs taken at sampling stations for various flow velocities and river bottom conditions. The visual impressions were compared with BOD measurements and possibility of recognition of water quality difference by photographs was examined.

The result suggested that higher velocity tended to give better water quality impression. When river bottom conditions were different, it was difficult to compare the impression of photographs. Photographs taken at appropriate velocities and under certain river bottom conditions were able to distinguish between BOD 1 and 5 mg/L.