BACKFLOW PHENOMENON IN THE TIP OF SALT WEDGE IN TIDAL AREA OF THE NISHI-UCHIKAWA RIVER, TOYAMA

Abstract

 The flow regime in the Uchikawa River (UR) where is located in Toyama Prefecture is extremely intricate because the channel network had been reformed. Especially, the west of the UR has been controlled by the government in order to manage water quality. The velocity distribution had been observed using the ADCP (acoustic Doppler current profiler) for 3 years in the UR. The water level, water temperature and electric conductivity had been measured at the same time. We had 88 days observation data.
 As a result of the observation, 57 distinct salt wedges were observed from 17:00-18:00 every time because of operation rule of the pumping station for water quality management. Moreover 37 distinct salt wedges had backward current in all layers near the tip of salt wedges. There has never been an observation like this before.