| Numerical simulations were used to determine the timing, flow path and driving forces controlling the movement of a high total dissolved solids (TDS) plume presently observed in the Mannville Group Aquifer (MGA). The present day and paleo-hydrogeology of Upper Devonian to Lower Cretaceous strata in south-central Alberta was simulated using a two-dimensional, variable-density, finite-element flow and transport model (SUTRA). The plume originated in the Cooking Lake Formation, then ascended through the Leduc reefs, travelled along and through the Nisku Formation and entered the MGA at the Wabamun subcrop. The results from the numerical simulations showed that a present-day topographic gradient (0.009) was insufficient to create the plume during the past 30 million years of tectonic dormancy. The results from paleo simulations (hydraulic gradients of 0.01, 0.007, and 0.004) showed that after 5 million years a hydraulic gradient of 0.007 created the best representation of the salinity distribution observed today. A sensitivity analysis supported the parameters used in the base case. |
