Beginning in the 1960s and increasing through to the present, regulation of reservoirs for hydroelectric generation has become more prevalent in the Nelson Churchill River Basin and the La Grande Rivière Complex. Coincident with hydroelectric regulation (HR), the effects of climate change have intensified and are more pronounced at higher latitudes, affecting the majority of the Hudson Bay Drainage Basin (HBDB). Whether the effects of climate change and HR are additive or offsetting is unclear, creating uncertainty as to the driving cause of the observed changes; with added complication from relatively poor representation of HR in continental-scale hydrologic models. This work aims to quantifiably distinguish the impacts of climate change (1981 – 2070) and HR on the majority of the freshwater supply to Hudson Bay by running two sets of hydrological simulations using the HYPE hydrologic model. The first set improves HR in HYPE, and the second simulates wholly re-naturalized conditions.