Heterogeneity Matters: Aggregation Bias of Gas Transfer Velocity Versus Energy Dissipation Rate Relations in Streams

The gas transfer velocity, [Formula: see text] , modulates gas fluxes across air‐water interfaces in rivers. While the theory postulates a local scaling law between [Formula: see text] and the turbulent kinetic energy dissipation rate [Formula: see text] , empirical studies usually interpret this relation at the reach‐scale. Here, we investigate how local [Formula: see text] laws can be integrated along heterogeneous reaches exploiting a simple hydrodynamic model, which links stage and velocity to the local slope. The model is used to quantify the relative difference between the gas transfer velocity of a heterogeneous stream and that of an equivalent homogeneous system. We show that this aggregation bias depends on the exponent of the local scaling law, [Formula: see text] , and internal slope variations. In high‐energy streams, where [Formula: see text] , spatial heterogeneity of [Formula: see text] significantly enhances reach‐scale values of [Formula: see text] as compared to homogeneous settings. We conclude that small‐scale hydro‐morphological traits bear a profound impact on gas evasion from inland waters.