Storage, mixing and release of water at the catchment scale

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Forested headwaters supply drinking water to half of the people living in North America and billions of people worldwide. And, in the past decade the forest hydrology community has found that stored water and the time it spends travelling through a catchment to the stream network can play a large role in landuse change outcomes in streams (quality and quality) draining forest land. But, in the past 5 years new isotope analysis of water from trees, soils, streams and groundwater has shown that water storage is compartmentalized in ways we are only just beginning to understand. Therefore, my NSERC Discovery Grant will go after this compartmentalization and investigate how forested catchments store, mix and release water by examining a set of key questions: Where do trees in the Canadian Boreal forest source their soil water and does the depth change throughout the hydrologic year? How do above and belowground physiological traits of trees affect water source depth distributions? How does water storage control the wide variance of streamflow responses to forest treatments at paired watershed sites across Canada? How do different soil water extraction techniques affect our interpretation of water sources, flow paths and transit times? Can we define a new age-based theory of the catchment water balance that explicitly represents storage, mixing and release of subsurface waters? These questions will be answered through a set of four interconnected Work Packages where HQP, field sites and laboratory methods will be strategically aligned. The work builds on influential accomplishments that my group has published in Nature, Nature-Geosciences, Nature-Sustainability, Nature-Climate Change and Scientific Reports over the past 6 years. The work engages several key strategic collaborators in Australia, China and Europe; designed to boost the research impact, network the 10 HQP involved in this proposal and help launch their early scientific careers. The proposed research program helps advance my long term goal of understanding runoff generation processes across diverse catchment systems, which will contribute to the classification of catchment behaviours and improved model formulations. This innovative work plan is aligned to the UN's Sustainable Development (SD) Goal 15 focused on `sustainable forest management'. The four Work Packages are coordinated to address key gaps in our ability to fulfil this SD goal. Closer to home, advances in our understanding of how forested headwater catchments store, mix and release water will be woven into the new Canada-Wide Global Water Futures program-led by the Global Institute for Water Security at the University of Saskatchewan in partnership with the University of Waterloo, McMaster University and Wilfred Laurier University-for better prediction and management of Canada's future water resources under changing climate and landuse.