Climatic controls on the water balance of a pilot-scale oil sands mining pit lake in the Athabasca oil sands region, Canada

ABSTRACT

Energy companies in the Athabasca Oil Sands Region in Alberta, Canada are evaluating the viability of incorporating pit lakes into reclamation closure designs to both sequester tailings and re-integrate the mining lease into the broader natural landscape. Lake Miwasin is a pilot-scale oil sands pit lake encompassed by a constructed catchment where the volume of the water cap is not actively managed. This study compared the water balance during the open water season over two consecutive years with contrasting levels of summertime precipitation. The first year had above average rainfall triggering surface water inflow events that diluted the over-winter water volume by ~ 25%. Flushing of the deepest layers of the water column was restricted from May – September as thermal stratification inhibited complete lake mixing. The second year had below average rainfall resulting in minimal surface water inflow and a drop in lake stage of ~ 30 cm. As the constructed catchment lacks both natural water bodies and connectivity to a legacy groundwater system, freshwater additions to the lake during the summer season were governed by rainfall. This research highlights challenges with constructing sustainable reclamation landscapes within a region characterised by variations in interannual and decadal water cycles.

KEYWORDS:

• Athabasca oil sands
• pit lakes
• reclamation
• tailings
• water balance
• hydrology

Acknowledgement

The Authors would like to thank Jennifer Attema, Adam Greeen, Tim Trembath, Kayla Jean-Marie Linden, Paola Correa Miramontes, and the Field Services team at Suncor Energy for field assistance with this research. We also thank Hatfield Consultants for providing site data and communications. Funding from a research grant awarded to SK and RP from Suncor Energy Inc. is greatfully acknowledged. We would aso like to acknowledge that this research takes place within the boundaries of Treaty 8, traditional lands of the Dene and Cree, as well as the traditional lands of the M’etis of northeastern Alberta.

Disclosure statement

The results we are presenting were completed through a research contract that was funded by Suncor Energy Inc., which places us in a financial conflict of interest. However, the results, interpretations and conclusions presented in the paper are unbiased and were not influenced by our funders in any manner.

Additional information

Funding

The work was supported by the Suncor Energy Incorporated.