Stable isotope ratios of tap water in the contiguous United States
Article first published online: 15 MAR 2007
Copyright 2007 by the American Geophysical Union.
Water Resources Research
Volume 43, Issue 3, March 2007
How to Cite
2007), Stable isotope ratios of tap water in the contiguous United States, Water Resour. Res., 43, W03419, doi:10.1029/2006WR005186., , , , and (
- Issue published online: 15 MAR 2007
- Article first published online: 15 MAR 2007
- Manuscript Accepted: 13 NOV 2006
- Manuscript Revised: 31 OCT 2006
- Manuscript Received: 18 MAY 2006
- hydrogen isotope;
- oxygen isotopes;
- water resources
 Understanding links between water consumers and climatological (precipitation) sources is essential for developing strategies to ensure the long-term sustainability of water supplies. In pursing this understanding a need exists for tools to study and monitor complex human-hydrological systems that involve high levels of spatial connectivity and supply problems that are regional, rather than local, in nature. Here we report the first national-level survey of stable isotope ratios in tap water, including spatially and temporally explicit samples from a large number of cities and towns across the contiguous United States. We show that intra-annual ranges of tap water isotope ratios are relatively small (e.g., <10‰ for δ2H) at most sites. In contrast, spatial variation in tap water isotope ratios is very large, spanning ranges of 163‰ for δ2H and 23.6‰ for δ18O. The spatial distribution of tap water isotope ratios at the national level is similar to that of stable isotope ratios of precipitation. At the regional level, however, pervasive differences between tap water and precipitation isotope ratios can be attributed to hydrological factors in the water source to consumer chain. These patterns highlight the potential for monitoring of tap water isotope ratios to contribute to the study of regional water supply stability and provide warning signals for impending water resource changes. We present the first published maps of predicted tap water isotope ratios for the contiguous United States, which will be useful in guiding future research on human-hydrological systems and as a tool for applied forensics and traceability studies.