Mapping submarine groundwater discharge at the Magdalen Islands

Marjorie Parenteau-Thibault, Jean-Michel Lemieux, Christophe Kinnard, Cecile Coulon, Alexandra Germain, Philippe Fortier

Dans les comptes rendus d’articles de la conférence: GeoNiagara 2021: 74th Canadian Geotechnical Conference; 14th joint with IAH-CNC

ABSTRACT: The Magdalen Islands in the Gulf of St. Lawrence are surrounded by salt water, causing groundwater to be the only source of drinking water for its inhabitants. Fresh groundwater in the archipelago is contained within a permeable red sandstone aquifer, and exists as a lens that overlies saline groundwater. Because of this configuration, exploitation of this aquifer requires complex management strategies due to potential saline intrusion in the pumping wells. Given the absence of any surface water bodies on the archipelago, the study of submarine fresh groundwater discharge (SFGD) is essential since it represents the only natural discharge for groundwater. SFGD is driven by differences in hydraulic head, and causes fresh groundwater to flow from the aquifer into the marine environment. Quantifying and mapping SFGD at the Magdalen Islands will allow for a refinement of the water budget and thus contribute to better management of local groundwater resources as impacted by climate change. Furthermore, mapping SFGD will supply additional data for the calibration of groundwater management models. The main objective of this study is to map the SFGD at the Magdalen Islands using thermal infrared remote (TIR) sensing. Unmanned aerial thermal infrared surveys allow for SFGD observation based on temperature contrasts at a given time in marine environments. However, several elements can affect the surface temperature in coastal waters, making the analysis of thermal infrared images challenging. In addition, there is little to no theoretical framework in the existing literature providing the appropriate methodology to assess the resulting images. In this study, surveys were carried out on multiple sites of the archipelago using a drone mounted with a TIR camera and a practical interpretation framework will be developed based on field observations and a numerical model to facilitate a standardized analysis of future TIR surveys.

Please include this code when submitting a data update: GEO2021_243

Retrouver cet article:
Les membres de la Société canadienne de géotechnique peuvent accéder à cet article, ainsi qu'à tous les autres articles de la Conférence Géotechnique Canadienne, dans le Espace membre. Les comptes rendus d'articles sont également disponibles dans de nombreuses bibliothèques.

Citer cet article: