Gas transfer velocity (k600) increases with discharge in steep streams but not in low‐slope streams

Abstract

Abstract Gas transfer velocity (k600) controls gas fluxes between aquatic ecosystems and the atmosphere. In streams, k600 is controlled by turbulence and, thus, local hydrology and geomorphology. Resultantly, variability in k600 can be large and modeling k600 from physical parameters can have large uncertainty. Here, we leverage a large dataset of k600 estimates derived from tracer‐gas experiments in 22 US streams across a range of discharges. Our analysis shows that k600 was highly variable both spatially across and temporally within streams, with estimates of k600 spanning three orders of magnitude. Overall, k600 scaled with discharge in steep streams due to relatively high stream power, but not in low‐slope streams, where stream power was relatively low even at high flows. Understanding how k600 responds to stream discharge in a wide variety of streams is key to creating temporally and spatially resolved estimates of biogeochemical processes in streams.