Dynamics of groundwater recharge and seepage over the Canadian landscape during the Wisconsinian glaciation

Abstract

[1] Pleistocene glaciations and their associated dramatic climatic conditions are suspected to have had a large impact on the groundwater flow system over the entire North American continent. Because of the myriad of complex flow-related processes involved during a glaciation period, numerical models have become powerful tools for examining groundwater flow system evolution in this context. In this study, a series of key processes pertaining to coupled groundwater flow and glaciation modeling, such as densitydependent (i.e., brine) flow, hydromechanical loading, subglacial infiltration, isostasy, and permafrost development, are included in the numerical model HydroGeoSphere to simulate groundwater flow over the Canadian landscape during the Wisconsinian glaciation ($À120 ka to present). The primary objective is to demonstrate the immense impact of glacial advances and retreats during the Wisconsinian glaciation on the dynamical evolution of groundwater flow systems over the Canadian landscape, including surface-subsurface water exchanges (i.e., recharge and discharge fluxes) in both the subglacial and the periglacial environments. It is shown that much of the infiltration of subglacial meltwater occurs during ice sheet progression and that during ice sheet regression, groundwater mainly exfiltrates on the surface, in both the subglacial and periglacial environments. The average infiltration/exfiltration fluxes range between 0 and 12 mm/a. Using mixed, ice sheet thickness-dependent boundary conditions for the subglacial environment, it was estimated that 15-70% of the meltwater infiltrated into the subsurface as recharge, with an average of 43%. Considering the volume of meltwater that was generated subsequent to the last glacial maximum, these recharge rates, which are related to the bedrock type and elastic properties, are historically significant and therefore played an immense role in the evolution of groundwater flow system evolution over the Canadian landmass over the last 120 ka. Finally, it is shown that the permafrost extent plays a key role in the distribution of surface-subsurface interaction because the presence of permafrost acts as a barrier for groundwater flow.

Effects of Permafrost Degradation on the Hydrological Regime in the Source Regions of the Yangtze and Yellow Rivers, China

“…Permafrost extent over a region plays a key role in the distribution of surface-subsurface water interactions [7,8,24,25]. Compared with non-permafrost regions, permafrost catchments have higher peak flow and lower base flow [20,26,27].…”

Groundwater in the Tibet Plateau, western China

“…Infiltration at the base of glaciers and snow packs provides a steady source of recharge to groundwater. The rate of recharge, however, is difficult to quantify in the absence of direct measurements and is a subject of active research [Lemieux et al, 2008]. We tested a range of recharge rates and arrived at 100 to 200 mm/year.…”

Geology and Hydrogeology of Faults on Cape Breton Island, Nova Scotia, Canada: an overview

“…This ice advance incorporated an ice sheet thickness of 2 to 3 km (Person et al 2007), as well as interaction between the main Laurentide Ice Sheet and the Appalachian ice complex. This resulted in the interplay of sea level change, ice sheet stability, pressure-focused sub-glacial recharge mechanisms (Person et al 2007;Lemieux et al 2008), and isostatic rebound within a lithologically and topographically diverse terrain (Stea et al 1998).…”