Observed and projected trends in spring flood discharges for the Upper Harricana River, eastern boreal Canada

Abstract

Study region: In northwestern Québec, the Upper Harricana River is representative of the Abitibi Plains’ hydrological dynamics over the last 250 years. Study focus: Planning for future spring flood risks involves uncertainties. This research presents a multicentury evaluation of changes in spring mean discharge and flood drivers using streamflow reconstruction (1771–2016), observations (1915–2020) and projections (2021–2100). New hydrological insights for the region: Using a downscaled CMIP5 ensemble of 10 global climate models (GCMs), generalized additive mixed modeling of mean spring discharge projections matched those of an independent mechanistic model and eight GCMs projected variability in spring discharge by 2100 to be similar to the historical variability reconstructed for the last 250 years across the Abitibi Plains. Results indicate that the projected decline in snow cover (–20 to –30% annual snowfall) and rise in winter and spring temperature may be offset by a greater contribution of rainfall to spring high discharge (+100 to +125 mm). However, two GCMs projected an increase in the magnitude and frequency of high mean spring discharge for the Abitibi Plains. By investigating future mean spring discharge for the Upper Harricana River in reference to past reconstructed variability, this study provides insights to inform the future management of regional water resources. The importance of estimating future regional flood risks from the behavior of multi-model ensembles is highlighted. © 2023 The Authors