Although bioclogging has been used for various applications, its performance has been unpredictable. We carried out a bioclogging experiment and developed a reactive transport model to understand and quantify geophysical responses to the production of a biopolymer (dextran) in a silica sand porous medium. The developed model was used to predict effectiveness of bioclogging and the associated geophysical signature under different treatment conditions. The porosity reduction calculated from the reactive transport modeling matched the concurrent increase in electrical resistivity and confirmed the dominant contribution of pore fluid conductivity to the bulk electrical conductivity. Correlations between measured electrical phase signals and predicted mineral surface area reduction indicated the controlling effect of mineral surface area on polarization. The joint use of the two methods quantitatively estimated the extent of decrease in porosity as well as effective mineral surface area, both of which are challenging to measure nondestructively in biological systems. The joint use of the geophysical methods and reactive transport modeling provided a better understanding of the dominant processes that govern dextran-based bioclogging and the associated geophysical responses. This opens new opportunities for quantifying changes associated with bioclogging processes and can potentially lead to new conceptual models that relate hydraulic property changes to the porosity and mineral surface area, which will enhance prediction, monitoring, and control of applications that use bioclogging.