Hydrology of a wetland-dominated headwater basin in the Boreal Plain, Alberta, Canada

•The basin received 55% more rainfall/month on average compared to climate normals.•Hydrologic connectivity between upland-wetlands was spatiotemporally variable.•Basin runoff driven by differences in the timing and magnitude of P relative to PET.•Runoff coefficients for storms ranged from <1 to >90%•Upland-wetland connections during wet periods generated substantial runoff.

This study provides an in-depth analysis of the runoff generation dynamics and hydrological connectivity across upland-wetland transitions within a wetland-dominated headwater basin in the Western Boreal Plain (WBP), Canada. Basin runoff response between and among years was driven largely by differences in the timing and magnitude of precipitation relative to potential evapotranspiration, hence antecedent moisture conditions, which varied markedly over the four-year study (April-Sept). Runoff coefficients for individual precipitation events ranged from <1 to >90% depending on storm dynamics and antecedent conditions. Owing to its higher elevation, the basin received 55% more precipitation per month on average compared to 30-year climate normals and an average of 86 mm more precipitation per season than the nearby regional weather station. The wetland and adjacent forestlands became coupled during intermittent wet periods which generated substantial runoff. The findings of the current study suggest that, in contrast to conventional conceptual models, headwater catchments within the subhumid WBP have the capacity to generate significant runoff throughout the snow-free period. This has important implications for wetland maintenance and represents an important water delivery mechanism for downstream ecosystems where excess water is scarce.