Ecohydrogeologic Investigation of Opportunistic and Constructed Wetlands on Syncrude’s Mildred Lake Lease

Initiation of wetland features is integral to sustaining landscape eco-hydrological function and meeting defined goals in surface mine reclamation. Within the sub humid climate of the Athabasca Oil Sands, Canada, the water generation mechanisms (external water sources, internal feedback mechanisms) that enable wetlands to form opportunistically on recently reconstructed landscapes are currently unknown, restricting flexibility in mine closure planning. To address this knowledge gap, we interpreted site and local physical characteristics of opportunistic wetlands within the Athabasca Oil Sands through a synoptic survey.

Wetlands formed opportunistically over a range of slopes, aspects and topographic positions. On coarse-textured landforms with large groundwater transmissivity, wetland formation was influenced by landscape-scale factors; wetlands were restricted to the toes of slopes and areas intersecting groundwater. On fine-textured constructed landforms, wetlands occurred on lower landscape elevations with potential for external (cumulative) water sources, and in hydrologically isolated locations with little potential for runoff contribution from adjacent forestlands. Wetlands formed on flat areas and in shallow inward draining endorheic pans with clay rich soils where low water storage potential promotes frequent surface saturation. These findings suggest passive techniques supporting internal feedback mechanisms may be more cost effective than more active, expensive techniques that aim to develop wetlands with external water sources.