Understanding Flow Pathways, Major Chemical Transformations and Water Sources Using Hydrochemical and Hydrometric Data in a Constructed Fen, Fort McMurray Alberta

English Abstract:

Bitumen extraction in the Athabasca oil-sands from open-pit mining creates significant landscape disturbance of wetland and forest ecosystems that must be returned to pre-equivalent capability, as required by Albert legislation. To date, reclamation activity has focused on upland ecosystems with more limited efforts on wetland and peatland ecosystems. Syncrude Canada Ltd. has constructed a 52 hectare upland-wetland system, the Sandhill Fen Watershed (SFW), to advance understanding on wetland reclamation strategies. The objective of this research is to identify and understand the sources, flow pathways and major chemical transformations of water as it moves throughout SFW. Surface and pore water samples from >20 well locations within SFW were analyzed for major chemical ions and oxygen and hydrogen stable isotopes. In addition, high frequency measurements of specific conductivity were recorded at 10 well locations to map salinity variability and how the SFW responsds to environmental changes. Stable isotopes have identified the source waters in SFW based on the dinstict signatures of input waters and the local meteoric water line. Major ion data has categorized the hydrochemical facies existing in the surface and subsurface waters of SFW and thus classifying areas with similar water composition. In addition, sodium adsorption ratios were evaluated to highlight areas where there is cation exchange between calcium and sodium, which is critical information for the success of vegetation. Major ion concentrations vary throughout SFW with values ranging from 100-500 mg/L and 50-650 mg/L for Ca and Na, respectively. Specific conductivity is also highly variable between the uplands and lowlands with values ranging from 1500-4000 µS/cm and 1000-2500 µS/cm. Collectively, the data provides insight to water sources, flow pathways and chemical changes within SFW, and provides insight into future evolution of the watershed.