Oxygen Transfer through Air Entrainment in Riparian Riffles: A Case Study of Seomjin River, Korea

Field investigation on the oxygen transfer through the air entrainment, the riffle geometries, and the relationships between the efficiency of the oxygen transfer and the hydraulic parameters in the riparian riffles were performed. Investigation of the air entrainment and measurements of the oxygen transfer in the riffles were conducted. Types of bed height in the riffles were upward convex. Slopes of the water surface and the river bed were steeper at the downstream rather than at the upstream part. Air entrainment occurred more frequently in the edged gravels rather than in the round and edgeless gravels, and it was formed mainly from behind the trailing edges of the gravels. Oxygen transfer was found to be proportional to the flow velocity, the flow discharge, and the Froude number, but not closely related to the particle diameter. Average value of oxygen transfer in the riffles of the study area was about 0.085, which shows good habitat condition for the aquatic creatures.