Hydrogeological Investigation of a Passive Wastewater Treatment System in a Thawing Permafrost Landscape

Abstract

The future performance of passive wastewater treatment systems, ubiquitous throughout arctic and sub-arctic communities, raises concerns due to permafrost thaw and increased groundwater activity. In turn, these communities face heightened water security risks due to the compounding impacts of climate warming, underinvestment in infrastructure, and limited mechanistic understanding of future changes. To address such risk, a cryohydrogeological model was developed to simulate the seasonal discharge of wastewater into a warming permafrost hillslope by the community of Fort Good Hope, Northwest Territories. By 2100, 14.5-33 metres of permafrost degradation along the hillslope is projected. Immediate and future contaminant transport concerns are presented due to rapid increases in hydrologic connectivity, and downgradient shifts in groundwater discharge zones, respectively. Recommendations include ground-truthing model results to address immediate contaminant transport concerns and enhancing model initialization and discretization for a precise characterization of annual groundwater trends at critical shifts in hydrologic connectivity.