The spatial and temporal controls on variability of the relative contributions of groundwater within and between flow systems to shallow lakes in the low-relief glaciated Boreal Plains of Canada were evaluated. Eleven lakes located in a coarse glacial outwash, of varying topographic positions and potential groundwater contributing areas, were sampled annually for stable O and H isotope ratios over the course of 8 years. It was demonstrated that landscape position is the dominant control over relative groundwater contributions to these lakes and the spatial pattern of the long-term isotopic compositions attributed to groundwater overrides interannual variability due to evaporative effects. Lakes at low landscape positions with large potential groundwater capture areas have relatively higher and more consistent groundwater contributions and low interannual variability of isotopic composition. Isolated lakes high in the landscape experience high interannual variability as they have little to no groundwater input to buffer the volumetric or isotopic changes caused by evaporation and precipitation. An alternative explanation that lake morphometry (area and volume) control long-term isotopic compositions is tested and subsequently refuted. Landscape position within coarse outwash is a strong predictor for relative groundwater input; however, surface-water connections can short circuit groundwater pathways and confound the signal. A hydrogeological case study for three of the study lakes is used to contextualize and further demonstrate these results.

It is necessary to understand the presence, movement, and persistence of contaminants in aquifers to develop adequate groundwater protection plans. Fractured bedrock aquifers with thin overburden cover are very sensitive to contamination, and little is known about transport processes from the ground surface to depth in this setting. This study was undertaken to investigate the potential of groundwater contamination by polybrominated diphenyl ethers (PBDEs), which are flame retardants, in a natural fractured bedrock aquifer in Canada proven to be sensitive to contamination. PBDEs, which had not been previously measured in groundwater in detail, were detected in the study aquifer at concentrations greater than those observed in surface-water bodies. Potential sources include manure, septic tanks, and the atmosphere. From this scoping study, it is evident that additional surveys of PBDE concentrations in groundwater are warranted, especially in settings with high potential source concentrations coupled with sensitive aquifers.

In Canada’s western Arctic, perennial discharge from permafrost watersheds is the surface manifestation of active groundwater flow systems with features including the occurrence of year-round open water and the formation of icings, yet understanding the mechanisms of groundwater recharge and flow in periglacial environments remains enigmatic. Stable isotopes (δ¹⁸O, δD, δ¹³CDIC), and noble gases have proved useful to study groundwater recharge and flow of groundwater which discharges along rivers in Canada’s western Arctic. In these studies of six catchments, groundwater recharge was determined to be a mix of snowmelt and precipitation. All systems investigated show that groundwater has recharged through organic soils with elevated PCO₂, which suggests that recharge occurs largely during summer when biological activity is high. Noble gas concentrations show that the recharge temperature was between 0 and 5 °C, which when considered in the context of discharge temperatures, suggests that there is no significant imbalance of energy flux into the subsurface. Groundwater circulation times were found to be up to 31 years for non-thermal waters using the ³ H-³He method.

This study evaluates the applicability of the chloride mass balance (CMB) method for groundwater recharge estimation in a semi-arid region in Canada, where recharge largely occurs under topographic depressions. The CMB applicability was tested at three scales: point-scale recharge rates at different topographical positions; average recharge rates incorporating multiple topographical positions on a local scale; and an identification of spatial trends of recharge on a regional scale. Agricultural chloride inputs were shown to be a major factor affecting chloride concentrations at all three scales, where elevated chloride concentrations in the shallow subsurface affected by agricultural inputs surpassed background concentrations by an order of magnitude. The propagation depth of elevated concentrations varied among study sites from being largely confined to the unsaturated zone to extending well into the saturated zone. Lateral chloride redistribution further affected the CMB applicability for point-scale recharge rates. Specific solutions enabling the CMB application in these conditions are presented, including runoff concentration measurements for point-scale estimates, using groundwater age tracers on a local scale, and using the harmonic mean concentration of a large number of samples on a regional scale.