Dissolved oxygen transfer into a square embayment connected to an open-channel flow

•DO recovery properties in embayment zone connected to open-channel flow is revealed.•DO is supplied to the embayment through the free-surface and the embayment/mainstream opening.•The aperture rate and opening position define the recovery rate.•A practical formula is proposed to predict the DO recovery rate based on experimental data. We have conducted field and laboratory experiments to determine the rates of processes responsible for the recovery of dissolved oxygen (DO) in an embayment connected to a main channel. We measured the horizontal velocity vectors to evaluate large-scale circulation within the embayment and measured the time series of DO concentrations during the recovery processes promoted by supply from the main channel. In particular, this study has focused on the effects of the aperture ratio of the embayment/main-channel opening. We have developed a practical formula for the DO recovery rate based on the bulk-mean velocity in the main channel, the aperture ratio, and the position of the embayment opening.