Hydrology of a Basin Fen Complex in Northeastern Alberta, Canada

Abstract:

The Western Boreal Plains (WBP) landscape is a mosaic of wetlands, lakes, and forested uplands, of which wetlands comprise nearly half. Along wetland-forestland transitions, dynamic ground/surface water interactions can have a strong influence on the quantity and chemistry of runoff to downstream basins. In a region affected by large-scale industrial development, there exists the need to better understand the hydrology of wetland-forestland complexes and their interactions, particularly over the long-term in order to capture inter-year climate variability. Pauciflora Basin (750 masl) is a 43 ha basin comprised of a poor fen bordered by forested uplands located on a prominent topographic high ~40 km SE of Fort McMurray (250 masl). Over the four-year study (April-Sept), the basin received 67% more precipitation (P) per month on average compared to 30-year climate normals and an average of 100 mm more P per season than the nearby regional weather station (360 masl). Wetland-forestland connectivity was highly dynamic both spatially and temporally but typically followed a trend of (1) upland water tables (UWT) sloping towards the wetland during spring and early summer and (2) a steady decline in UWT as the season progressed leading to flow reversals and decoupling. Runoff generation from the catchment was typically greatest in the spring and early summer when wetland and forestlands were coupled. However, runoff remained sensitive to P throughout the season for most years due to frequent rain events in excess of 20 mm d^-1. Inter-year variability in storage on UWT appeared to be driven by slope characteristics, and upland runoff to the fen was high when UWT was within the more hydrologically active soil layer, which may influence solute and runoff processes downstream. Headwater catchments with above average P and significant wetland-upland connectivity may represent an important water supply for downstream catchments in an otherwise subhumid climate.