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Stratigraphic sequence map for groundwater assessment and protection of unconsolidated aquifers: A case example in the Abitibi-Témiscamingue region, Québec, Canada

2017; Taylor & Francis; Volume: 43; Issue: 2 Linguagem: Inglês

10.1080/07011784.2017.1354722

1918-1817

Simon Nadeau, Éric Rosa, Vincent Cloutier,

Groundwater flow and contamination studies

Quantifying water resources at various scales is crucial for ensuring safe access to potable water for present and future generations. Fitting into this framework, this study presents a GIS-based approach aimed at allowing the evaluation of available groundwater resources within unconsolidated aquifers set in vast and heterogeneous shield regions. The approach was developed in a 19,397 km2 region located in Abitibi-Témiscamingue (Québec, Canada) where unconsolidated aquifers are set in an irregular geologic framework owing to the rugged Canadian Shield topography and to the diversity of glacial and post-glacial events that shaped the landscape. Sparse and unevenly distributed stratigraphic borehole data were used for constructing a GIS-based model representing the total overburden thickness (unconsolidated sediments covering the bedrock), as well as the thickness and extent of the fine-grained deep-water sediments (silt-clay) of the Barlow-Ojibway proglacial Lake on a 100 m × 100 m mesh at the regional scale. The study suggests a new set of functions to map drift thickness in areas of highly discontinuous drift cover, using GIS tools. These data were used jointly with surficial deposits maps in order to develop a regional-scale two-dimensional model where 15 distinct stratigraphic sequences allow representation of the architecture of unconsolidated geological units. The approach allows simplifying data representation and ensuring the consistency between various regional-scale hydrogeological maps. The data is used to produce a stratigraphic sequence map for representing the architecture of aquifer– aquitard systems at the regional scale in a manner that is intelligible to non-specialists. The map and related data are first discussed for documenting the extent and volume of regional aquifers. The stratigraphic sequence map is subsequently discussed as a tool for supporting political decision makers dealing with issues related to groundwater resource assessment, protection and sustainable development.