Tap water isotope ratios reflect urban water system structure and dynamics across a semiarid metropolitan area

Abstract

Water extraction for anthropogenic use has become a major flux in the hydrological cycle. With increasing demand for water and challenges supplying it in the face of climate change, there is a pressing need to better understand connections between human populations, climate, water extraction, water use, and its impacts. To understand these connections, we collected and analyzed stable isotopic ratios of more than 800 urban tap water samples in a series of semiannual water surveys (spring and fall, 2013–2015) across the Salt Lake Valley (SLV) of northern Utah. Consistent with previous work, we found that mean tap water had a lower 2H and 18O concentration than local precipitation, highlighting the importance of nearby montane winter precipitation as source water for the region. However, we observed strong and structured spatiotemporal variation in tap water isotopic compositions across the region which we attribute to complex distribution systems, varying water management practices and multiple sources used across the valley. Water from different sources was not used uniformly throughout the area and we identified significant correlation between water source and demographic parameters including population and income. Isotopic mass balance indicated significant interannual and intra‐annual variability in water losses within the distribution network due to evaporation from surface water resources supplying the SLV. Our results demonstrate the effectiveness of isotopes as an indicator of water management strategies and climate impacts within regional urban water systems, with potential utility for monitoring, regulation, forensic, and a range of water resource research.

In situ monitoring of H and O stable isotopes in soil water reveals ecohydrologic dynamics in managed soil systems

“…After irrigation, the cycling of water back to the atmosphere through evaporation and transpiration is altered by distinctive land uses and land cover materials (Schirmer, Leschik, & Musolff, 2013). Despite the prevalence of isotope-enabled hydrologic studies in a variety of natural settings, the use of H and O stable isotopes in water in hydrologically managed systems has been largely focused on studying water supply and transfers in cities (e.g., Ehleringer et al, 2016;Good, Mallia, Lin, & Bowen, 2014;Jameel et al, 2016). Despite the prevalence of isotope-enabled hydrologic studies in a variety of natural settings, the use of H and O stable isotopes in water in hydrologically managed systems has been largely focused on studying water supply and transfers in cities (e.g., Ehleringer et al, 2016;Good, Mallia, Lin, & Bowen, 2014;Jameel et al, 2016).…”

Isotopic reconnaissance of urban water supply system dynamics

“…Recent work has shown the capacity of 525 water isotopes to record information about water management and quantify effects of climatic variability on water resources (Jameel et al, 2016;Tipple et al, 2017). Moving beyond the coarse resolution of these studies, our work has highlighted the ability of water isotopes to provide information about PWSS operation at a much finer scale.…”

“…In these cases, the values observed at the same well during other months were used to characterize water supplied from this well. This substitution was justified given that previous work showed little temporal variability in the isotope values of water supplied from SLV groundwater wells (Jameel et al, 2016). isotope values (differences in for δ 2 H and δ 18 O less than 0.5‰ and 0.1‰ respectively) were also combined together for our analyses (such as wells 64S and 70S in June, July and August, 2015).…”

“…5). Our model builds upon the work of Jameel et al (2016) and Tipple et al (2017), but goes beyond their analyses by providing quantitative, spatially-and temporally-resolved estimates of source contributions at 315 locations throughout the SLV supply system. According to our model, most of the distribution sites (45 out of 65) received most (>70%) of their water from a single source.…”

“…Here, geochemical tracers such as the stable isotopes in water (SIW) can also serve as a tool to study water management within complex urban distribution systems. Recent studies have shown that distributions of the SIW in urban areas relying on multiple water sources can be used to characterize active water management practices, identify linkages between socioeconomic 80 factors and water management practices, and quantify the effects of climate variability on water resources (Jameel et al, 2016;Tipple et al, 2017).…”