EARLY WATER DYNAMICS WITHIN A WETLAND COMPLEX CONSTRUCTED ON TAILINGS AT AN OIL-SAND MINE

Oil-sand mine operators in north-eastern Alberta seek to demonstrate the viability of constructing wetlands (fens or bogs, in particular) on reclaimed mine landscapes. Syncrude Canada Ltd. has constructed the Sandhill Fen Research Watershed, a reclaimed area with uplands and lowlands designed for forestland and wetland development. The experimental watershed was constructed on mine tailings deposited within a former open pit where the tailings contain slightly elevated sodium concentrations from the ore and processing. The reclamation surface consists of mechanically placed sand hummocks and flat areas of various forms with different reclamation cover and upland vegetation prescriptions. Research and eventual operational concerns include quantifying the impacts of consolidation of the underlying tailings, of possible migration of process-affected water into reclamation materials, and of variations in water budget components due to the sub-humid climate.

Instrumentation and monitoring activities include: over 200 piezometers and wells with manual and continuous measurements of water level, electrical conductivity and temperature, plus water sampling; over 200 access tubes and automated sensors for measurement of soil-moisture content distributions; 32 automated tensiometers; bi-weekly mapping of saturated and flooded areas; two eddy covariance stations to measure evapotranspiration rates; three full meteorological stations and other hydrometeorological instrumentation. Wetland and forestland vegetation are regularly surveyed and inventoried. We are approaching the end of the third year of operation (i.e., since reclamation material was placed, planted and instrumented). Shallow groundwater and surface water in the primary fen area are highly responsive to precipitation events and water management activities. Deeper groundwater levels and water tables below the hummocks are gradually rising as the system appears to wet-up with fresh water. Isolated areas intended to become perched fens show variable degrees of water retention capability. There is some evidence that small amounts of tailings water enter from adjacent deposits, from either below or laterally; however, detrimental effects on vegetation are neither evident nor anticipated.