T.B. Coplen N.L. Haas D. A. Saad M. A. Borchardt R. J. Hunt 2005 <p><span>Because surface water can be a source of undesirable water quality in a drinking&nbsp;<a title="Learn more about water well" href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/water-well" data-mce-href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/water-well">water well</a>, an understanding of the amount of surface water and its travel time to the well is needed to assess a well's vulnerability. Stable&nbsp;<a title="Learn more about isotope ratios" href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/isotope-ratios" data-mce-href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/isotope-ratios">isotope ratios</a>&nbsp;of oxygen in&nbsp;<a title="Learn more about river water" href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/river-water" data-mce-href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/river-water">river water</a>&nbsp;at the City of La Crosse, Wisconsin, show peak-to-peak&nbsp;<a title="Learn more about seasonal variation" href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/seasonal-variation" data-mce-href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/seasonal-variation">seasonal variation</a>&nbsp;greater than 4‰ in 2001 and 2002. This seasonal signal was identified in 7 of 13 city municipal wells, indicating that these 7 wells have appreciable surface water contributions and are potentially vulnerable to contaminants in the surface water. When looking at wells with more than 6 sampling events, a larger variation in&nbsp;</span><i>δ</i>¹⁸<span>O compositions correlated with a larger fraction of surface water, suggesting that samples collected for oxygen&nbsp;<a title="Learn more about isotopic composition" href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/isotopic-composition" data-mce-href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/isotopic-composition">isotopic composition</a>&nbsp;over time may be useful for identifying the vulnerability to surface water influence even if a local&nbsp;<a title="Learn more about meteoric water" href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/meteoric-water" data-mce-href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/meteoric-water">meteoric water</a>&nbsp;line is not available.</span></p><p>A time series of<span>&nbsp;</span><i>δ</i>¹⁸<span>O from one of the municipal wells and from a&nbsp;piezometerlocated between the river and the municipal well showed that the travel time of flood water to the municipal well was approximately 2 months; non-flood arrival times were on the order of 9 months. Four independent methods were also used to assess time of travel. Three methods (groundwater temperature arrival times at the intermediate piezometer, virus-culture results, and&nbsp;particle tracking&nbsp;using a numerical&nbsp;groundwater-flow&nbsp;model) yielded flood and non-flood travel times of less than 1 year for this site.&nbsp;Age dating&nbsp;of one groundwater sample using&nbsp;</span>³H–³He methods estimated an age longer than 1 year, but was likely confounded by deviations from piston flow as noted by others. Chlorofluorocarbons and SF₆<span>analyses were not useful at this site due to degradation and contamination, respectively. This work illustrates the utility of stable hydrogen and&nbsp;oxygen isotope ratios&nbsp;of water to determine the contribution and travel time of surface water in groundwater, and demonstrates the importance of using multiple methods to improve estimates for time of travel of 1 year or less.</span></p> application/pdf 10.1016/j.jhydrol.2004.07.010 en Elsevier Investigating surface water-well interaction using stable isotope ratios of water article