Reactive transport models contain terms describing microbiological and hydrological processes that control fate and transport of contaminants in porous media. Most models assume that microbial reaction rate is independent of microbial biomass distribution or that biomass is uniformly distributed across media surfaces in a manner that mass transport does not limit reaction rate. Experimental data, as well as some computational models, however, suggest otherwise, indicating a need to experimentally establish how the coupling of microbial biomass and flow distribution influence microbial reaction rates. Nuclear magnetic resonance techniques offer the opportunity to quantify in three dimensions the coupling of microbial biomass and flow velocity distribution in opaque porous media at multiple scales in a noninvasive manner. Experimental data obtained with these techniques can be used to improve the accuracy of boundary conditions used by reactive transport models to predict contaminant fate and transport at the pore and core scales. Further improvements in surface and subsurface magnetic resonance techniques may allow future detection and measurement of microbial biomass distribution in the subsurface at the field scale.