RESEARCH ON EFFECT OF DRAINAGE WORKS FOR IMPROVEMENT OF WATER QUALITY IN THE CHANNEL OF SMALL TOWN AREA

This research is one of the field survey on the self-purification of the contaminated river water in a small town area, in which the undertaking of drainage works has been underconstructed during about 8-years. The field survey basin is about 5 km2 area and about 3.6km length of channel and then six-stations are decided for measuring points of water quality such as temperature, DO, conductivity, BOD, T-N, and T-P, still more volume of flowing water. The results obtained during 8-years are discussed about time series change characteristics. Especially, the purification effects of BOD, T-N, and T-P were maked clear by rate values of improvement relating to the diffusion ratio of drainage.