Seasonal Variability of Groundwater Contribution to Watershed Discharge in Discontinuous Permafrost in the North Klondike River Valley, Yukon

Abstract

The objectives of this thesis were: (1) to quantify seasonal groundwater contribution to total stream discharge and (2) further our understanding of sub-arctic carbon sources and pathways within a sub-arctic discontinuous permafrost river catchment. Twenty-two samples were taken from the North Klondike River, 14 samples from 5 of its tributaries, and 46 rain and snowmelt samples from the Dawson City Airport, Yukon, Canada,. During the winter months, groundwater is responsible for greater than 95% of total river discharge. Spring freshet and summer flow bring snowmelt and precipitation, contributing anywhere from 30% to greater than 60% of total river discharge. Groundwater is characterised by high concentrations of geogenic solutes from weathering during recharge, dissolved inorganic carbon, and carbon-14 activities of 0.61 pMC. Tritium activities indicate a fast moving system, with groundwater ages measuring less than 10 years. The most significant discharge of organic carbon from the system is during spring freshet (434,192 kg carbon). Primary productivity within the system is estimated to be 10.2 grams of carbon per metre squared, with approximately 96% of carbon being sequestered or emitted as carbon dioxide.