The Hydrological Function and Connectivity of a Basin Fen-Bog Complex in Northeastern Alberta, Canada

English Abstract:

Within the Western Boreal Plains (WBP) wetlands comprise up to 65% of the landscape, the majority of which are peatlands. However, hydrologic interactions between classes within peatland complexes are not as thoroughly understood and the influences of regional-scale connections beyond the local-scale and over the long-term are required. Accordingly, this research aims to advance our understanding of the hydrological function of peatland classes within a peatland complex and to place this into the context of regional connectivity within the WBP setting. We examined the hydrology of a ~11 ha basin fen-bog complex situated within the Stony Mountain range ~40 km south of Fort McMurray. The low-lying basin depression forms an elongated hourglass-shaped configuration and is bordered by upland slopes. The bog is located at the topographic high within the peatland system and a small mineral upland marks the sharp transition between the bog and fen. Within the fen, peat thickness ranged from >12 m in the lower lobe to ~3 m in the bog. For the entire basin, the peat profile thinned rapidly towards the bordering uplands. Water table levels were typically close to or above the surface for most years and mirrored surface topography along the bog-fen sequence, with ground and surface water flowing from the bog towards the fen for the majority of the season. However, during dry periods, groundwater flow direction temporarily reversed and the water table sloped towards the bog. During precipitation events, the bog water table exhibited a ~12 hour lag in response compared to the water table within the fen. While vertical hydraulic gradients indicated that the basin was a groundwater recharge feature, the rate of recharge was minimal due the low hydraulic conductivity of the surrounding slopes and mineral substrate underlying the peat. The large storage capacity of the upland moss layer was rarely exceeded and shallow groundwater and surface flow was also low. Precipitation totals for the growing season were always well above the regional average and was the dominant input for the basins water balance. This study highlights the hydrologic function and varying interactions that can take place within bog-fen complexes in the subhumid Boreal Plains.