Impact of glaciation on groundwater vulnerability

点击翻译按钮获取中文摘要

Source water protection is a priority as population growth, climate change and contaminants have put pressures on groundwater producing wells. Approximately 11.5 million Canadians and 2 billion people worldwide rely on groundwater for drinking and daily use, with additional significant use by agriculture (60% of groundwater withdrawn) and industry (20%). These vulnerable resources are found in glacial deposits or bedrock of previously glaciated regions in Canada and around the world. Managing and protecting water wells requires a robust geological model that identifies the geometry of hydraulically relevant features at the well field or contaminant plume scale. Creating this type of model is challenging in previously glaciated settings, where texture is not the primary driver controlling groundwater flow or contaminant pathways. The last glaciation had a profound impact not only on texture, but also on the variable distribution of subsurface materials, the surface topography, and the underlying bedrock surface. In addition, the permeability of bedrock was affected through fracture and dissolution feature or karst development associated with crustal rebound and glacial and post-glacial hydraulics. This geological history plays a key role in determining modern contaminant pathways and plume evolution, volume and depth of aquifers, integrity of aquitards, and consequently, flow system characteristics, well productivity and susceptibility to contamination. While geological surveys and the environmental sector have made strides in creating regional scale models, the heterogeneity of glacial deposits at the well field scale remains a challenge. The proposed research addresses this by 1) identifying typical sedimentation styles or architecture in specific glacial settings, and assessing its influence on water quality; and 2) examining the interactions between glacial processes and the underlying bedrock and how this has impacted karst distribution in bedrock aquifers. Numerous high-resolution core and water quality data will be examined to test if certain landscapes and subsurface sediment profiles are more susceptible to contamination than others, thus improving delineation of wellhead protection areas. The relationship between glacial processes and bedrock will be explored by examining a) the geological evolution of a buried bedrock valley and its relationship to the occurrence of productive karstic bedrock aquifers and b) the geological properties of the sediment-bedrock interface to shed light on subglacial processes and to assess if there are any predictive relationships useful for subsurface modelling and protection of contact aquifers. Research findings and 5 graduates with the much-needed skills of applying glacial geology to hydrogeology will have a significant impact on Canada's ability to protect groundwater at the well-field scale, by advancing our understanding of the geological history of these previously glaciated landscapes.