Multi-scale controls of soil water dynamics and connectivity

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Although soil water represents <0.001 of water in the global hydrological cycle, it is a life-sustaining resource for all inhabitants of Earth’s terrestrial ecosystems. Food, fiber and fuel production is strongly dependent on the availability of soil water for plants. It also determines various ecosystem services such as food and freshwater, regulates flood, and controls the solubility and transport of agrochemicals and wastes (via runoff). Understanding how storage and transport of soil water and soluble materials within the soil water (e.g. nutrients, agrochemicals) occurs requires knowledge about how fast water travels (as surface and subsurface runoff) and which path it takes to reach streams and rivers. However, these processes are often disrupted by preferential flow paths that create (dis)connection between different points. I refer this (dis)connection in transport processes as ‘soil water connectivity’. Examining the connectivity is essential for a number of important fundamental and applied problems that have emerged in the geoscience including the role of soil water dynamics in global water cycle and protection of surface water bodies from pollution. The proposed research focuses on the connectivity of soil water within the vadose zone (root zone) and will use advanced field and laboratory based tools and computer models. During this grant period, my core research questions are: 1) what exactly is connectivity, 2) how can we define, measure, and model connectivity, and 3) can we relate the connectivity to recent research? These questions will be examined through four testable hypotheses in studies conducted by 3 PhD and 2 MSc students with the help of 4 undergraduate summer interns over the next 5 year. These studies will 1) better define the dynamics of soil water connectivity at different scales within a catchment which will lead to soil water being included in more hydrologic, climate and land-surface models and 2) show the critical nature of soil water for flood management (through the onset of runoff, flow connections), diffuse pollution mitigation and thus the improvement of environmental health. Over the long term, the research program will address fundamental questions about vadose zone hydrological dynamics at multiple spatial/temporal scales and their participation in the global water cycle. This research program will maintain and build Canada’s profile in water resources management, which is particularly relevant today due to the global concern about sustaining the supply of potable water and protecting fresh water bodies from pollution, for human and environmental health.