Isotope-based water balance assessment of open water wetlands across Alberta: Regional trends with emphasis on the oil sands region

Study region: Water sampling for stable isotopes (O-18 and H-2) was carried out during 2009-2019 across Alberta, Canada, as part of a survey targeting 1022 open water wetlands. The study presents the first site-specific wetland water balance assessment spanning Grassland, Parkland, Foothills, Mountains, and Boreal regions, including the oil sands region, a corridor of rapid development.& nbsp;Study focus: Climate reanalysis, watershed data, and isotopic data for wetlands were incorporated into a steady-state isotope mass balance model, and applied to estimate site-specific evaporation losses from the wetlands, as well as runoff, groundwater inflow, total outflow, and seasonal drawdown. Regional-scale water balance fluxes, water balance indicators and site-specific classifications were mapped and described.& nbsp;New hydrological insights for the region: Systematic variations in evaporation losses, watershed runoff to wetlands, wetland discharge, and net groundwater inflow are revealed across the major subregions of Alberta including the oil sands region. Isotope balance calculations suggest that 13% of wetlands are predominantly evaporative, 87% have surface and/or groundwater outflow, 90% have positive water yields, 47% likely have groundwater inflow, and 2% are apparently fed by allochthonous water sources (either snow or glacial melt). For the 3 oil sands regions, a scoping survey suggests that between 20% and 40% of wetlands within the bitumen zones are detectably groundwater reliant compared to 35-50% in the wider vicinity of the deposits.