CHARACTERISING GROUNDWATER SURFACE-WATER FLOW PATTERNS AT A WETLAND CONSTRUCTED ON WASTE ROCK IN THE OIL SANDS REGION

Wetlands make up half of the natural landscape in the Fort McMurray oil sands region. Consequently, sustainable wetlands must be established on reconstructed landscapes following mining. The successful creation of constructed wetlands and surrounding forestlands is essential to returning reclaimed areas to equivalent landscape capability. The dominant factor in the establishment, maintenance, evolution, and persistence of a wetland is hydrology. An eight year study was conducted on Bill’s Lake, a wetland located on a low permeability saline-sodic overburden waste dump, to evaluate the primary hydraulic controls and movement of water as this reclaimed site transitions into a mature landform. Hydraulic processes such as snow redistribution, runoff, water uptake, and evapotranspiration are influenced by vegetation succession on reconstructed landscapes. This succession will influence the water balance, representing the dominant processes at that time. A better understanding of the hydraulic processes controlling reclaimed wetlands will help determine the requirements for establishing sustainable wetlands on reclaimed waste mine dumps.

The water balance from 2005 through 2012 was examined to determine the hydraulic processes dominating this landform, and how they change throughout time. Hydrometric data reveal that evapotranspiration and precipitation dominate the water balance of the wetland. Water levels and stage elevation are highest in spring following snow melt, and decrease throughout June and July, when evapotranspiration is greatest. Water levels do not recover until after snow melt the following spring. Shallow groundwater flow reversals occur along some edges of the wetland, and are controlled by changes in water storage within the wetland and the adjacent hillslopes. Although precipitation and evapotranspiration dominate, sufficient snow melt runoff from adjacent hillslopes occurs to sustain the wetland system. Identifying and better understanding these flow reversals and patterns on constructed wetlands can be used to generate successful environments in future reclamation efforts.