Charity Kgotlaebonywe / Earth & Environmental Sciences / Faculty Mentor: Ricardo Sanchez-Murillo
Understanding tap water distribution dynamics is critical for sustainable urban management, especially in rapidly growing cities facing climate variability and water scarcity. This study uses water stable isotopes (δ18O and δ2H) in rainfall, reservoirs, and tap water to understand the spatiotemporal structure of drinking water distribution systems in the City of Gaborone (Botswana) and Arlington, Texas (USA). Spatial and temporal (2022-2024) clustering analysis and Bayesian mixing models reveal water origin and water blending contributions across the distribution system. Clustering analysis revealed the prevalence of similar water sources across Gaborone during winter (N=3) and summer (N=3): a) groundwater and b) surface water (Dikgatlhong and Gaborone dams). In Arlington, three groups were identified during both summer (N=3) and winter (N=3), corresponding to isotope signatures from Lake Arlington and Richland Chambers and Cedar Creek reservoirs. Tracer fingerprints consistently suggest groundwater mixing occurring within both tap water systems. Isotope time series identified the arrival of a 1,000-year rainfall event (treated water) signal to Arlington’s tap water system, roughly seven days after a large flooding event in the DFW area. Our results show the sensitivity of water isotopes to detect tap water engineering practices and pose a new paradigm for drinking water quality monitoring during extreme flooding events in a changing climate.
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