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. (C) 2018 Elsevier Ltd. All rights reserved.