Parameterization of a channel network model for groundwater flow in crystalline rock using geological and hydraulic test data

Groundwater flow in sparsely fractured crystalline rocks is highly channelized due to the existing complex hydrogeological heterogeneity in fracture networks. The impacts of multiscale hydraulic heterogeneity on channelized flow in a block of fractured rock under the unidirectional flow condition are investigated by three-dimensional (3D) discrete fracture network (DFN) modeling. A channel network (CN) model generated from DFN is used to model the channelized groundwater flow in fractured crystalline rock. An approach for parameterizing the channel conductance is proposed which uses information from the hydrogeological characterization data. The results show that the network scale hydrogeological heterogeneity dominates the distribution variability of flowrates. The proposed parameterization approach for the channel conductance is effective and robust. Based on the available hydrogeological characterization data, it is possible to compensate for the neglected heterogeneity in the CN model by enhancing the variability of assigned channel conductance. The findings from this work are useful for model simplification from 3D DFN to CN, and for overcoming the difficulty in the parameterization of CN models in applications.

Automated summary

The highly channelized groundwater flow in sparsely fractured crystalline rocks is affected by multiscale hydraulic heterogeneity in fracture networks. This study investigates the impacts of the heterogeneity on channelized flow using three-dimensional discrete fracture network modeling. A channel network model is used to simulate the groundwater flow in fractured crystalline rock, and a parameterization approach for channel conductance is proposed. The results show that the hydrogeological heterogeneity at the network scale dominates the variability of flowrates, and the proposed approach is effective in compensating for neglected heterogeneity in the model.