Strategy for evaluating channeling in the carbonate bedrock at Smithville, Ontario

Groundwater flow through carbonates typically results in a network of solutionally-enlarged channels (or conduits). These transmit much of the flow yet occupy only a small fraction of the void space in the aquifer. Since boreholes are unlikely to intersect the channels, standard aquifer tests are unable to characterize channel flow, and a novel strategy is needed. Four strategies are being used in the dolostone aquifer at Smithville to characterize channeling. First, passive in situ monitoring of water level, temperature and electrical conductivity is being used to show which boreholes show the rapid response to storm events that is characteristic of channeling. Second, cross-borehole pressure pulse and tracer tests reveal fracture connectivity and flow velocity. Third, two analog sites are being used for comparison. One is a nearby quarry where channeling is indicated by point discharges in the quarry face. The other is in a well-developed karst area, where aquifer test data is available for comparison with Smithville. The final strategy is to add channel flow to the existing FRAC3DVS model, and to compare simulations with and without channeling to existing aquifer test data.