Inferring groundwater contributions and pathways to streamflow during snowmelt over multiple years in a discontinuous permafrost subarctic environment (Yukon, Canada)Inférence des contributions sur de nombreuses années de l’eau de nappe et passage d’écoulement durant la fonte de neige dans un environnement de permafrost subarctique discontinu (Yukon, Canada)Inferencias de las contribuciones de agua subterránea y de las trayectorias hacia una corriente en el derretimiento de nieve durante múltiples años en un ambiente subártico de permafrost discontinuo (Yukon, Canada)不连续亚北极永久冻土环境下多年融雪期地下水对河川径流的贡献及途经的推断(加拿大育空地区)Inferindo os percursos e a contribuição da água subterrânea para o escoamento superficial durante o degelo, ao longo de vários anos, num ambiente de permafrost subártico (Yukon, Canadá)

Research on large northern rivers suggests that as permafrost thaws, deeper groundwater flowpaths become active, resulting in greater baseflow, increased concentrations of weathering ions and reduced concentrations of dissolved organic carbon in the streamflow. In contrast, at the headwater-catchment scale, where understanding of groundwater/surface-water interactions is developed, inter-annual variability in climate and hydrology result in complex hydrological and chemical responses to change. This paper reports on a 4-year runoff investigation in an alpine discontinuous permafrost environment in Yukon, Canada, using stable isotopes, major dissolved ions and hydrometric data, to provide enhanced insight into the inter-annual-variability runoff-generation processes. Stable isotope results suggest that pre-event (old) water stored within the catchment dominates the snowmelt hydrograph, and dissolved ion results reveal that groundwater pathways occur predominantly in the near-surface during freshet. Dissolved organic carbon varies inter-annually, reflecting changing melt patterns, whereas weathering ions generated from deeper flowpaths become diluted. The total snow-water equivalent does not have a major influence on the fraction of snowmelt water reaching the stream or the runoff ratio. Results from multiple years highlight the considerable variability over short time scales, limiting our ability to detect climate-change influences on groundwater at the headwater scale.