Landscape control of water chemistry in northern boreal streams of Alberta

End-member mixing analysis (EMMA) and isotopes of water (deuterium and oxygen-18) are used to describe hydrologic processes for six boreal forest catchments in the discontinuous permafrost of northern Alberta. The data presented in this paper represent pre-disturbance conditions during two average precipitation years for small basins where the impacts of clear cut harvesting will be evaluated in future work. Hydrologic patterns and soil water sources were different between the two streams draining sloped catchments and the four streams draining flat lowlands. In sloped catchments, snowmelt discharged rapidly prior to loss of soil frost. Snowmelt discharge initially contained between 70 and 90% water from mineral soils and peatlands. As melt progressed, soil water was replaced by surface or near-surface runoff comprising 50–80% of stream discharge. Surface storage of snowmelt in sloped catchments was minimal and summer stream discharge was dominated by rainfall routed through organic and mineral soils (34 and 46%, respectively). Surface runoff averaged 20% of total discharge throughout the summer but rose to 60% of discharge following large storms. In contrast, snowmelt was stored in lowland catchments; peak snowmelt discharge was 30–66% of summer peak discharge and was an equal mix of older groundwater and snowmelt. In lowland catchments, watertables and stream flow declined through the summer and summer discharge was increasingly dominated (>50%) by groundwater routed through organic soils.