The inherent variability of streams makes quantifying physical, chemical, and biological interactions challenging. Spatial variability in point-scale biogeochemical measurements makes it difficult to assess the controls on reaction rates as well as the net effect of any one type of sub-environment on whole-stream reaction rates. Adopting the hot spot viewpoint, it is likely that only a fraction of a stream reach is biogeochemically active, but the location and the magnitude of the reactions is still in question. This presentation will discuss an on-going method development for reach-scale analysis of spatially varying biogeochemistry. The process involves defining relevant eco-hydraulic patches based on protocols for describing sediment texture with detailed hydraulic measurements relating to mass transfer. These factors interact to produce conditions that either enhance or inhibit a target biogeochemical process of interest, and the variables used to describe the sediment and hydraulic conditions can be included into dimensional analysis for the development of widely applicable scaling relationships. The usefulness of this eco-hydraulic methodology will be presented using recent data collected from a field investigation examining dissolved oxygen dynamics in the south fork of the Iowa River located in central Iowa.