DEVELOPMENT OF A CHRONOSEQUENCE-BASED CONCEPTUAL MODEL FOR ANTICIPATING THE IMPACT OF LANDSCAPE EVOLUTION ON GROUNDWATER RECHARGE IN DEGRADING PERMAFROST ENVIRONMENTS

The impacts of permafrost degradation have been studied in the discontinuous permafrost zone at Umiujaq, in northern Quebec, Canada, for over 30 years, but the effects of changing land cover on groundwater recharge is not well understood. This study attempts to gain insight into how changing landcover alters the timing and volume of recharge, in addition to investigating the time scale over which these changes occur. To accomplish these goals, the water table fluctuation (WTF) method was used to compute groundwater recharge using four years of water level data and soil moisture readings from five field sites characteristic of different stages of permafrost degradation and vegetation invasion. Results indicate that as vegetation grows taller, groundwater recharge increases, likely due to increased snow thickness. Results were then combined with a preexisting conceptual model that describes the evolution from tundra to shrubland and forests to create a new model for describing how groundwater recharge is affected by landscape evolution. Finally, results estimated using the WTF method were compared to recharge values computed using a suite of 1-D heat and water flow models in order to determine whether differences in recharge timing and volume are caused by process-based changes occurring in both the saturated and unsaturated zones.