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WATER RESOURCES RESEARCH, VOL. 43, W03419, doi:10.1029/2006WR005186, 2007

Stable isotope ratios of tap water in the contiguous United States

Gabriel J. Bowen

Earth and Atmospheric Sciences Department, Purdue University, West Lafayette, Indiana, USA
Biology Department, University of Utah, Salt Lake City, Utah, USA


James R. Ehleringer

Biology Department, University of Utah, Salt Lake City, Utah, USA
IsoForensics, Inc., Salt Lake City, Utah, USA


Lesley A. Chesson

Biology Department, University of Utah, Salt Lake City, Utah, USA


Erik Stange

Biology Department, University of Utah, Salt Lake City, Utah, USA


Thure E. Cerling

Biology Department, University of Utah, Salt Lake City, Utah, USA
IsoForensics, Inc., Salt Lake City, Utah, USA


Abstract

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 δ 2H) at most sites. In contrast, spatial variation in tap water isotope ratios is very large, spanning ranges of 163‰ for δ 2H and 23.6‰ for δ 18O. 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.

Received 18 May 2006; accepted 13 November 2006; published 15 March 2007.

Keywords: hydrogen isotope; oxygen isotopes; water resources.

Index Terms: 1041 Geochemistry: Stable isotope geochemistry (0454, 4870); 1819 Hydrology: Geographic Information Systems (GIS); 1848 Hydrology: Monitoring networks; 1884 Hydrology: Water supply.

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Citation: Bowen, G. J., J. R. Ehleringer, L. A. Chesson, E. Stange, and T. E. Cerling (2007), Stable isotope ratios of tap water in the contiguous United States, Water Resour. Res., 43, W03419, doi:10.1029/2006WR005186.