Weirs are frequently constructed in lowland rivers for commercial or recreational boat navigation, gravity-fed diversion of water for human use, and aesthetics. High respiration rates associated with elevated organic matter loading can lead to a decline in dissolved oxygen concentrations with adverse consequences both for water chemistry and aquatic biota. Models of oxygen balance within rivers frequently assume a constant diffusion coefficient to model reaeration at the air-water interface. This paper demonstrates that in low-velocity aquatic environments such as weir pools, reaeration rates can be dependent on wind or flow-induced turbulence in the surface layers that promote mixing of dissolved oxygen. We parameterise this effect within a one dimensional oxygen balance model and the model is fitted to field measurements in a weir pool in northeastern Victoria, Australia. There is great utility of the resulting model for targeting environmental flows for managing risks of anoxia. The role of flow in preventing anoxic events through its influence on reaeration rates can be critically important in lowland rivers.