Arctic regions face a unique vulnerability to shifts in seasonality, which influences the summer recharge potential of freshwater reservoirs caused by decreased precipitation and increased evaporative stress. This pressure puts small remote northern communities at risk due to limited existing freshwater supply. The lack of baseline knowledge of existing supply, demand, or reservoir recharge potential increases this risk. We therefore address this knowledge gap through a water resource assessment of municipal supply over a 20 year planning horizon in two communities in Arctic Canada using a novel heuristic model and existing data sources. We generated climate and demand scenarios to identify the mechanisms of drawdown, as well as examine the influences on replenishment. We found a pronounced vulnerability to reduced winter precipitation and/or increased ice-thickness of reservoirs. Our heuristic supply forecasts indicate an immediate need for freshwater management strategies for northern communities in Canada.