Title: Simulating hydroelectric regulation and climate change in the Hudson Bay drainage basin.
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, together making up close to half of the total freshwater flux entering Hudson Bay annually. Coincident with hydroelectric development, 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 hydroelectric regulation are additive or offsetting is unclear, creating uncertainty as to the driving cause of the observed changes; with added complication due to the relatively poor representation of regulation in continental-scale hydrologic models. This work aims to quantifiably distinguish the impacts of climate change and hydroelectric regulation on the majority of the freshwater supply to Hudson Bay by running two parallel sets of hydrological simulations using the HYPE model. The first set improves reservoir regulation in HYPE, and the second creates a wholly re-naturalized set of simulations with no anthropogenic influence. An ensemble of the Phase 5 Climate Model Intercomparison Project (CMIP5) general circulation models (GCMs) and representative concentration pathways (RCPs) drive simulations over the HBDB at a daily time-step from 1981 to 2070. By subjecting both models (regulated and re-naturalized) to climate change, the effects of hydroelectric regulation can be isolated and quantifiably distinguished from climate change. This research improves the performance of a hydrological model in a highly regulated system, and further succeeds in distinguishing the spatio-temporal scales of different change factors. Intra-annual changes of flow timing are primarily due to hydroelectric regulation, inter-annual change is driven by upstream storage, and inter-decadal impacts are the result of climate change. With these results, a variety of additional simulations (i.e., sea-ice, carbon-cycling, biogeochemical) can be run to ascertain the overall health of Hudson Bay and the effects of climate change and reservoir detention can be attributed quantitatively.