Identification and Preliminary Quantification of Groundwater-Surface Water Exchanges Driven by Near-Surface Glacial Geology in Two Boreal Peatlands of Northeastern Maine, USA

Groundwater flow patterns have been previously investigated in the peatlands of northeastern Maine, USA, using geophysical methods and hydrologic models. The structure and stratigraphy of glacial geology are thought to regulate groundwater fluxes within the peatlands of northeastern Maine. These fluxes alter peatland hydrology, potentially influencing the formation of pool systems and other features of peatland geomorphology. Our recent work in this domain focused on the identification and preliminary quantification of zones of focused groundwater discharge to the surface of two boreal peatlands using temperature and subsurface electrical conductivity as tracers. Tracers were supported by radar imaging of subsurface structure and stratigraphy. Handheld thermal cameras, direct point temperature sensors, and aerial thermal imagery were used to identify seepage hot spots caused by groundwater upwelling in the peatlands. Electromagnetic induction surveys were used to map apparent conductivity contrasts that confirmed the vertical and lateral extent of seepage zones. Ground penetrating radar surveys provided insight into the spatial relationship between peatland basin morphology and groundwater upwelling. Vertical temperature profilers, consisting of individual temperature loggers at varying depths, were installed within selected hotspots to begin to quantify groundwater fluxes based on changes in the diurnal temperature signals with depth. Integrated hydrogeophysical methods for identifying areas of enhanced groundwater fluxes establish background for preliminary quantification of the hydrologic processes occurring within northern boreal peatlands. Peatlands are complex systems with unique physical hydrologic processes controlling internal biogeochemical reactions. Preliminary quantification of enhanced groundwater discharge zones in northern boreal peatlands may have implications for quantifying the processes of methane production and release.