Origin and Flow Dynamics of Perennial Groundwater in Continuous Permafrost Terrain using Isotopes and Noble Gases: Case Study of the Fishing Branch River, Northern Yukon, Canada

Abstract

Perennially flowing groundwater discharges along a 15‐km section of the Fishing Branch River, Yukon causing open water during winter and numerous discrete springs near Bear Cave Mountain. Groundwater flow occurs in karstified marine carbonate rocks as well as in alluvial river talik(s). The PCO2 and δ13C indicate groundwater dissolves CO2 during recharge in organic soils and weathers limestone in the aquifer. These analyses show three groundwater chemistry groups and variability in surface water chemistry. The variations in water chemistry are related to differences in the rocks exposed in the recharge area. The δ18O and δ2H results show that groundwater represents approximately the annual average of precipitation based on samples collected in the region. Noble gases were used to determine that the recharge temperature lies between 0 and 5 °C which suggests that recharge happens during the summer. Groundwater ages, calculated using 3H‐3He dating, were found to be between 0 and 17.7 years. River discharge was measured during spring and summer under different water‐level conditions. Winter baseflow was calculated based on summer discharge measurements and the width of the river channel in winter. Although river flow decreases in winter, groundwater discharge maintains open water. Copyright © 2012 John Wiley & Sons, Ltd.

Groundwater hydrogeochemistry in permafrost regions

“…Hydrogeochemical tracers, either alone or in combination, can offer important insights for developing groundwater conceptual models extending from recharge areas to discharge areas . Classical tracers used for such studies include major ions which can provide a first estimate for groundwater circulation, stable isotopes (of carbon and water) which provide insight into the origin of recharge, radioactive isotopes which are used as dating tools, and noble gases which provide information about recharge temperatures .…”

“…Hydrogeochemical tracers, for example, have been effective for understanding water–permafrost interactions in extreme environments such as hypersaline springs in the high Arctic or in the active layer in the Antarctic . Detailed interpretations involving major ions, water isotopes, DIC, DOC, and carbon isotope reactions together with noble gases for groundwater characterization in permafrost setting are presented by Utting et al and Lapp et al…”

“…Futhermore, studies have shown the importance of groundwater on baseflow of arctic rivers. 27,33,36,37,39,63,64 Impacts of groundwater quality on river water quality should therefore also continue to be investigated.…”

“…To account for the complex interactions between groundwater and permafrost under changing climatic conditions, groundwater flow dynamics must be better characterized. To fill this data gap, hydrogeochemical characterization, including major ions, nutrients, stable isotopes and dating tools, has therefore also been very useful to gain insight into flow systems including residence times and recharge conditions …”

“…To fill this data gap, hydrogeochemical characterization, including major ions, nutrients, stable isotopes and dating tools, has therefore also been very useful to gain insight into flow systems including residence times and recharge conditions. 37,39,40 The natural hydrogeochemistry in permafrost-degrading areas is also of direct interest if the resource is to be used for drinking water or industrial use. In areas where groundwater quality is at risk from development, knowledge of baseline groundwater quality (i.e., before development) is especially critical for identifying and evaluating potential future impacts, in particular for distinguishing possible impacts of development from natural transient events or impacts due to climate change, including permafrost degradation.…”