Landuse and climate change: Impacts on Ontario's water resources

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Land use and land cover (LULC) are dynamic in many developed parts of the world, and this is particularly true in southern Ontario, where nearly ¼ of the Canadian population resides and where climatic and soil conditions are most favourable for agriculture. Indeed, agriculture ubiquitously surrounds urban areas in S. Ontario, and this intersection between prime agricultural land and a large and growing population poses particular challenges for water resources. Climate variability is also the norm and the impacts of climate shifts and extreme weather on water resources are often amplified in developed landscapes. However, there are few studies of hydroclimatic perturbations in developed landscapes that have seasonal snow cover, and generally there has been a greater focus on precipitation extremes during the warm season (i.e. storms, droughts). In addition, there have been few, if any studies of the interactive impacts of so-called sustainable' LULC and climate variability at the watershed scale. The observation that LULC can amplify the sensitivity of water resources to climate change inspired the proposed research program, which has two primary questions: (1) how have past and current LULC and climate shifts affected water quantity and quality in southern Ontario? And, (2) are sustainable' practices having the desired effect? These questions will be addressed through a variety of approaches, utilizing existing long-term monitoring data as well as new, spatially and temporally intensive watershed-based measurements. Research will be focused in the Lake Ontario basin, extending between Toronto and Belleville and from the Lake Ontario shoreline northwards to the Oak Ridges Moraine. This area is particularly appropriate for disentangling the cumulative influence of climate and LULC change on water quantity and quality because it is undergoing both urban expansion and agricultural intensification as well as shifts in land use practices. It is also home to the Seaton Development area, which has been designated a sustainable urban community' and is unique in Canada. Importantly, this part of Ontario does not have the same long history of intensive agriculture as the Lake Erie basin and therefore many of the regional long-term water quantity and quality monitoring stations were established before change began. While a variety of water quality parameters will be measured, the primary focus of this research will be on the major nutrients: carbon, nitrogen and phosphorus.