A multi-model study of the subsurface and surface hydrodynamics of a 700 km2 watershed in western Canada (Fox Creek area, Alberta)

A 700 km 2 watershed near the town of Fox Creek (west-central Alberta, Canada), a region that has seen intensive oil and gas production since the 1950s, is investigated. The overall objective is to improve our understanding of the hydrodynamics of this watershed. The hierarchical multi-model approach uses physically based numerical models and follows a stepwise progression, transitioning from saturated and variably saturated groundwater to integrated surface water–groundwater (SW-GW) models. This progression encompasses 2D and 3D configurations from a deep (∼1 km) hydrogeological multi-layer aquifer system to a shallow (45 m) coupled flow system. This differs from other multi-model studies where the focus is on comparing simple to complex models for a fixed domain. The hierarchical modeling approach has led to better insights and estimates of processes including vertical recharge and lateral groundwater contributions. Moreover, it allowed us to corroborate hydraulic conductivity values and groundwater recharge despite the limited dataset. The hydraulic connections between the four non-marine bedrock units were shown to be negligible, allowing us to focus on the Paskapoo Formation. The unsaturated zone was shown to play a significant role in the model response, and accounting for land surface–subsurface dynamics was demonstrated to be critical to properly estimating hydraulic head profiles and land surface saturation patterns. • Hierarchical approach led to a better understanding of the study area hydrodynamics. • 2D and 3D models, with and without a sediment cover and unsaturated zone, were used. • In a first step, interactions between bedrock formations were found to be weak. • Subsequently, fine-grained sediment cover was found to greatly impact recharge. • Generally, SW-GW coupling was able to reproduce land surface saturation patterns.