WETLAND-GROUNDWATER EXCHANGE AT A GLACIAL OUTWASH ENVIRONMENT IN THE WESTERN BOREAL FOREST

Wetland-Groundwater exchange at a sand and gravel deposit in Northern Alberta, Canada, is being studied as part of a long-term, multi-disciplinary research project to evaluate impacts of anthropogenic disturbance and temporal climate variation. The hydrologic system has been instrumented with piezometers, seepage meters, thermistor strings, and other hydrological and meteorological instrumentation to determine spatial and temporal components of the water budget. Site geology is composed of 15 metres of outwash sand and gravel over more than 20 metres of clay till. Ground surface depressions (5-10 metres deep) are filled with pond and peatland complexes, which include fine-grained lake sediments and organic material (peat and gyttja).

The wetland is supplied by groundwater discharge and there is no surface-water inflow to the wetland system. Surface outflow through a small channel to an adjacent lake, is the major component of outflow. Precipitation and evaporative fluxes are approximately equal. Thus, groundwater inflow and surface-water outflow dominate the water budget. Differential variability of wetland and groundwater levels has resulted in seasonal groundwater flow reversals. The freeze-thaw cycle for the wetland perimeter, which is composed of a 30 metre wide band of peat, lags pond freeze-thaw by two months.

Observed wetland-groundwater exchange will be simulated using a coupled, surface-water-groundwater model. Simulations will be used to test the role of freezing and thawing cycles on wetland hydrology, investigate the impact of climate variation on wetland sustainability and predict the impact of disturbances to the Boreal Forest from events such as logging and road building.