Coupling the soil catena to the runoff enigma in Canada's Boreal Plain

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Canada's Boreal Plain stretches from the Rockies to Lake Winnipeg and the Prairies to the northern Taiga ecozones. The amounts of water flowing in its rivers and streams depend on how rainfall is divided between losses to the atmosphere through evaporation and transpiration and that which is stored in its lakes, wetlands, and soils. Determining the redistribution and storage of water between landscapes and waterways is key to understanding stream flows at larger scales. Despite the importance of understanding the flow of water to all aspects of our environment and activities, we do not have enough data to quantify and interpret our studies: runoff in the Boreal Plain remains an enigma. This research aims to understand runoff processes in the mid-to-lower regions of the Athabasca River Basin. However, hydrological measurements for these regions are scant, which limits our ability to interpret and predict runoff variability and trends. Given the large-scale industrial activities in this region, a changing climate, and recent natural disasters, we urgently need to solve this runoff enigma.******A soil catena is a sequence of soils found down a slope. The soil hydraulic properties and layering in a catena greatly affect local runoff. Rainfall events on forested hillslopes can cause transient runoff that impacts adjacent wetlands, lakes, and streams. Enhanced hydrological connectivity between hillslopes and wetlands through transient runoff could result in a significant additional mechanism of runoff generation not yet considered. The hydraulic properties of the soils in a catena affect the timing and magnitude of transient runoff, so understanding these properties is crucial to understanding the hydrological processes and stream flows at both the local and regional scales. Since flow pathways affect water quality, transient runoff pathways could also result in geochemical changes that influence the health of downstream ecosystems.******The long-term objectives are to identify and understand new mechanisms of water movement within the Boreal Plain and to evaluate their significance for regional-scale runoff. This field-based program will study the transient hydrological connections between wetlands and forested hillslopes. Soil layering along the catenae of multiple hillslopes will be evaluated to assess spatial variability and runoff potential. Laboratory measurements of soil hydraulic properties will complement field results. Innovative hillslope runoff stations at forestlandwetland boundaries will measure lateral hillslope runoff during rainfall events. Subsurface flow pathways along the soil catenae will be determined using tracer tests. These new mechanisms of water movement will be combined with existing hydrological models and compared to observations of water availability and quality within the Athabasca River Basin. This is an important contribution to the conceptualization of water movement in this industrially and ecologically significant region.