Quaternary geology of southern Ontario and applications to hydrogeology

Abstract

Quaternary geology of southern Ontario and applications to hydrogeology IntroductionThe southern Ontario (lowland) region is a sedimentary basin covering ϳ72 000 km 2 located within the Great Lakes watershed (e.g., Sharpe et al. 2014a). It is bounded by Canadian Shield to the north and east, and three Great Lakes to the south and west (Ontario, Erie, and Huron). The region is the economic heartland of Canada accounting for over 40% of the Canadian Gross Domestic Product. It contains one-third of the Canadian population and has the highest population density in the country. The Great Lakes cumulatively account for approximately 84% of North Americas available freshwater and form the largest potential transboundary groundwater -surface-water resource between the USA and Canada (Environment Canada and the U.S. Environmental Protection Agency 2014). Ironically, there is significant reliance on groundwater for potable, commercial, and agricultural water uses. Approximately 3 million people use groundwater in Ontario, with the majority of these located in southern Ontario. Extraction by domestic systems support ϳ1.3 million people and ϳ1.9 million people use municipal supplies (e.g., Waterloo, Guelph; Sharpe et al. 2014b).For a decade, from 2004 to 2015, groundwater studies in Ontario were dominated by the Source Protection Program that the provincial ministries of Environment and Climate Change, and Natural Resources and Forestry funded via Conservations Authorities in 22 Source Protection areas. The focus of this work was largely water budget modeling, the identification of threats to drinking water supplies, and the establishment of wellhead protection areas around municipal wells. This program was complemented by the Ontario Geological Survey's groundwater initiative, which focused on the collection and interpretation of new, high quality subsurface geoscience information to support regional groundwater understanding (Bajc et al. 2016). This research was a direct outcome of the recommendations of the Walkerton Inquiry (O'Connor 2002) that followed on the tragic events in a southwestern Ontario community where the water supply was compromised by poor wellhead design and lax water treatment checks and protocols, following a heavy rain event in the spring of 2000. Over 2000 people became ill, 7 people died, and the conservative, tangible cost to the provincial economy, up to 2002, was over $60 million (Livernois 2002).The O'Connor Report (2002) recognized the early leadership in Ontario of the Ontario Geological Survey and Geological Survey of Canada in providing the understanding on geologic controls to support knowledge of groundwater and surface-water relationships. Importantly, geological conceptualization is often the first step of any hydrogeological study as it provides important information about geometry and connectivity of units that may support withdrawal of large amounts of water, and the distribution and integrity of units that may act as a barrier to flow and contaminants. A robust geological framework ...

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