System dynamics approach to assess the sustainability of reclamation of disturbed watersheds1

The mining of oil sands in northern Alberta leaves behind large open pits, tailings, and overburden piles in which the surface and subsurface hydrology has been completely disrupted. Extensive reclamation work is required to reconstruct the entire landscape and reestablish the various elements of the hydrologic cycle. Syncrude Canada Ltd. has established a series of small instrumented watersheds in a reclaimed overburden pile at the Mildred Lake mine in northern Alberta, Canada, to test the sustainability of different reclamation strategies. The purpose of these field sites is to assess the performance of different reclamation strategies and track the evolution of the reclaimed landscape with time. The saline–sodic shale overburden has been covered with different (in type and depth) soil layers to provide sufficient moisture storage for vegetation while minimizing runoff and salt transport into the cover from the underlying overburden shale. In this paper, a system dynamics watershed model (SDWM) is developed to simulate one of the reconstructed watersheds and assess its ability to provide common watershed functions. The model is at an early stage, but preliminary results point to the potential of the system dynamics approach in simulating watersheds and testing different scenarios. The tested reclamation strategy seems to be satisfactory within a certain range of hydrologic conditions. Further validation of the SDWM is required, however, before relying on its results for decision support with regard to reclamation strategies.