title: Thermal Imagery of Groundwater Seeps: Possibilities and Limitations.
abstract: Quantifying groundwater flow at seepage faces is crucial because seepage faces influence the hydroecology and water budgets of watersheds, lakes, rivers and oceans, and because measuring groundwater fluxes directly in aquifers is extremely difficult. Seepage faces provide a direct and measurable groundwater flux but there is no existing method to quantitatively image groundwater processes at this boundary. Our objective is to determine the possibilities and limitations of thermal imagery in quantifying groundwater discharge from discrete seeps. We developed a conceptual model of temperature below discrete seeps, observed 20 seeps spectacularly exposed in three dimensions at an unused limestone quarry and conducted field experiments to examine the role of diurnal changes and rock face heterogeneity on thermal imagery. The conceptual model suggests that convective air-water heat exchange driven by temperature differences is the dominant heat transfer mechanism. Thermal imagery is effective at locating and characterizing the flux of groundwater seeps. Areas of active groundwater flow and ice growth can be identified from thermal images in the winter, and seepage rates can be differentiated in the summer. However, the application of thermal imagery is limited by diverse factors including technical issues of image acquisition, diurnal changes in radiation and temperature, and rock face heterogeneity. Groundwater discharge rates could not be directly quantified from thermal imagery using our observations but our conceptual model and experiments suggest that thermal imagery could quantify groundwater discharge when there are large temperature differences, simple cliff faces, non-freezing conditions, and no solar radiation.
authors: Department of Civil Engineering, McGill University, Macdonald Engineering Building, 817 Sherbrooke Street West, Room 492, Montréal, Québec, H3A 0C3, Canada.
authors: Erin
authors: E
authors: Mundy
authors: Tom
authors: T
authors: Gleeson
authors: Department of Civil Engineering, McGill University, Macdonald Engineering Building, 817 Sherbrooke Street West, Room 492, Montréal, Québec, H3A 0C3, Canada.
authors: Mark
authors: M
authors: Roberts
authors: Département de génie de la construction, École de technologie supérieure, 1100 rue Notre-Dame Ouest, Montréal, Quebec, H3C 1K3, Canada.
authors: Michel
authors: M
authors: Baraer
authors: Department of Earth and Planetary Sciences, McGill University, 3450 University Street, Montreal, Quebec, H3A 0E8, Canada.
authors: Jeffrey M
authors: JM
authors: McKenzie
mesh_terms: D060587:Groundwater; D060106:Lakes; D009792:Oceans and Seas; D045483:Rivers; D014872:Water Movements