Spatial variations in tap water isotopes across Canada: Tracing water from precipitation to distribution and assess regional water resources

• Published in: PLOS Water
• Main Authors: Bhuiyan, Shelina A., Jameel, Yusuf, Chartrand, Michelle M. G., St-Jean, Gilles, Gibson, John, Bataille, Clément P.
• Other Authors: Nóbrega, Rodolfo, Canadian Security and Safety Program Targeted Investment, Chemical, Biological, Radiological and Nuclear Research & Technology Initiative
• Format: Article in Journal/Newspaper
• Language: English
• Published: Public Library of Science (PLoS) 2023
• Subjects: Canada; glacier*
• Online Access: http://dx.doi.org/10.1371/journal.pwat.0000068; https://dx.plos.org/10.1371/journal.pwat.0000068

With global warming and increasing water use, tap water resources need sustainable management. We used hydrogen and oxygen isotope analyses in tap water (i.e., δ 2 H and δ 18 O values) to identify issues associated with tap water resources in Canada. We analyzed 576 summer tap samples collected from across Canada and 76 tap samples from three cities during different seasons and years. We classified the samples based on their sources: groundwater (Tap Groundwater ), river (Tap River ) and lake (Tap Lake ). δ 2 H values in tap water correlate strongly with values predicted for local precipitation across Canada with a stronger correlation for Tap Groundwater and Tap River than for Tap Lake. We then constructed water balance models to predict the δ 2 H of surface water across Canada, and validated them against Canadian stream δ 2 H data. δ 2 H values in tap water correlate strongly with values predicted for local surface water, however, the water balance models improved the predictability only for Tap River and Tap Lake and not for Tap Groundwater . Tap Groundwater δ 2 H values reflect the δ 2 H values of annually averaged precipitation, whereas Tap River and Tap Lake δ 2 H values reflect post-precipitation processes. We used the δ 2 H residuals between the observed and predicted δ 2 H values to assess regional processes influencing tap water δ 2 H values across Canada. Regionally, snow/glacier melt contributes to all tap sources around the Rockies. Tap waters are highly evaporated across Western Canada, irrespective of their sources. In the Great Lakes and East Coast regions, tap waters are evaporated in many localities, particularly those using surface reservoirs and lakes. We propose the use of these isotopic baselines as a way forward for the monitoring of tap water resources at different scales. These isotopic baselines also have valuable applications in human forensic studies in Canada.