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About Dr. Macrae:

Merrin Macrae is a Professor in the Department of Geography and Environmental Management at the University of Waterloo. Dr. Macrae received her B.E.S. and M.Sc. degrees from York University and her Ph.D. from Wilfrid Laurier University. Her research interests center around nutrient (nitrogen, phosphorus) dynamics and water quality in agricultural landscapes and wetlands. Dr. Macrae studies water quality at both watershed and field scales, with an emphasis on assisted drainage. A key aspect of her work involves understanding the winter and snowmelt periods, and the efficacy of beneficial management practices during these critical times. Her research largely field-based science, focused in Southern Ontario and Manitoba. 

Key Areas of Specialization:

1. Effects of Hydroclimatic and Landscape Drivers on Biogeochemical Processes in Agricultural Systems


This topic has been a significant focus of my research program. I am interested in winter processes, as these drive annual nutrient loss budgets in cold regions, yet are poorly understood. Also, the "winter" period may experience vastly different conditions both across and within regions. We are working to build an improved understanding of cold season processes into advanced hydrologic models, which are important in upscaling as well as projecting the impacts of climate change. We are also exploring the relevance of different event ‘types’ and antecedent conditions on nutrient mobilization through preferential transport, fill and spill and surface inundation or through the release of legacy P. We have also identified landscape drivers such as regional differences in soil biogeochemistry and their associated risk for P loss in runoff

 stream in autumn    winterLON    stormField


2. Determination of linkages between hydrologic flowpaths and nutrient mobilization in agricultural systems

My team is developing an advanced understanding of the contribution of tile drains relative to surface runoff in annual and seasonal P losses at the edge of field in contrasting environments. As part of this research focus, we have worked toward understanding mechanisms driving variable responses in tile drains. We have used a range of approaches including geochemical tracers, blue dye staining techniques, temperature and hydrograph analyses to quantify the contribution of preferential transport to P mobilization in tile drainage. 




3. Improved understanding of mechanisms driving the efficacy of management practices in reducing phosphorus mobilization in agricultural systems

Much of the ongoing debate surrounding uncertainty in the efficacy of conservation practices relates to the fact that conditions, dominant processes and hydrological and biogeochemical flowpaths vary within and across different geographic regions in response to climate and landscape drivers. Consequently, solutions to water quality challenges also differ across these regions. My lab has explored the impacts of a suite of conservation practices across different landscapes.