A reactive transport model was constructed to investigative how the carbonate-evaporite aquifer system within the Devonian Elk Point Group in northeast Alberta has evolved over geologic time and to evaluate connectivity in the present system. The mineable area of the Athabasca Oil Sands overlies the Elk Point Group where regional dissolution of halite and anhydrite has eroded the Prairie Evaporite Formation from a thickness of approximately 260 m to as thin as 20 m. Groundwater chemistry changes along the flowpath towards the Athabasca River, reflecting the evaporite distribution. Water types change from bicarbonate- to sulphate- to chloride-types, and salinities increase exponentially toward saturation with respect to halite. The model was constructed as a 1-D domain in PHREEQC to simulate the regional dissolution of the evaporites, using hydraulic testing results, isotopic data, and the measured hydrochemistry to constrain the transport parameters. The dual porosity function in PHREEQC was needed to calibrate the model to the measured chloride distribution over the 90 km-long model domain, indicating the role of mass transfer from poorly-connected regions of the aquifer system. The simulated duration of the regional dissolution was on the order of 50,000 to 500,000 years, suggesting that the phases of dissolution postulated from geologic evidence from the pre-Cretaceous to the Holocene (Stoakes et al. 2014a) may have consisted of relatively shorter pulses of dissolution. Two types of accelerated anhydrite dissolution and dedolomitization are identified for the current conditions: anhydrite/gypsum removal by low-TDS, bicarbonate-dominated waters and increased anhydrite/gypsum solubility with higher salinity. Both of these processes appear to be occurring within approximately 20 km east of the Athabasca River. Reactive transport modelling of the regional system may help to identify local areas of karst development and vertical connection to open-pit mines in the overlying McMurray Formation.