A STUDY ON VARIABILITY CHARACTERISTIC OF WATER QUALITY IN TIDAL AREA OF URBAN RIVER

Abstract

In order to clarify variability characteristic of water quality in tidal area of urban river, results of field observation at ordinary water (about the water quality change before and after dredging) and rainfall in the tidal area of the Nihonbashi River are reported in this paper. From the results of field observation, following results are obtained;1) The mean value of dissolved oxygen saturation of all layers decreased by 25.8% at the spring tide, by 20.4% at the neap tide before and after dredging. 2) BOD concentration decreased and T-P concentration increased after dredging. T-N concentration decreased after dredging at the low tide. 3) When total rainfall was 10.5mm in 7 hours, value of dissolved oxygen saturation did not change in all layers, and it increased by 20% after 7 days. 4) During daytime both air temperature and water temperature increased. On the other hand, during nighttime water temperature decreased in spite of air temperature increased. 5) Water velocity repeated reverse flow and uniform flow during a hour period.