It has been observed that groundwater flow through fractures is channelized due to variations in fracture aperture, fracture roughness and different fracture intersections. Nevertheless, a common practice in DFN modelling is to model each fracture as hydraulically homogeneous, which is an obvious simplification of reality. In our study, we have evaluated whether a flow-calibrated DFN model, where each fracture is assumed hydraulically homogeneous, can reproduce the particle tracking behavior of a more realistic DFN model where each fracture is hydraulically heterogeneous. We used a concept of a synthetic reality where a model with heterogeneous hydraulic properties was used to produce simulated field data measurements to provide a benchmark for particle tracking analyses. Multiple synthetic reality models were used to reproduce a borehole pumping test mimicking a Posiva Flow Log (PFL) tool. Results from the pumping tests served as a calibration target for a model with the same fracture geometry, but homogeneous fracture properties. PEST ® was used as a tool for the calibration of homogeneous models so that they match the distribution of inflows obtained from the synthetic reality model. By using PEST®, it was possible to successfully calibrate a homogeneous models so that the distribution of inflows matched results from the synthetic reality model. A particle tracking analysis was then conducted on both heterogeneous and calibrated homogeneous models. Particle pathways were statistically analyzed in terms of particle travel distance, travel time and F-factor, which is a key parameter governing the transport of radionuclides within fractured rock. Results show that homogeneous calibrated models can produce non-conservative results in terms of the F-factors. In our study, we have demonstrated that DFN models successfully calibrated to boreholes inflow data could give a poor prediction in terms of particle tracking analysis.

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