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Frontiers in Water


Isotopic analyses of delta O-18 and delta H-2 of water in the context of the hydrologic cycle have allowed hydrologists to better understand the portioning of water between the different water domains. Isoscapes on a large spatial scale have been created to show isotopic variation in waters as a function of elevation, temperature, distance to coast, and water vapor source. We present the spatial and temporal isotopic results of precipitation, surface water, and groundwater of an ongoing study across Massachusetts, USA in order to establish an isotopic baseline for the region. This represents one of the most comprehensive and detailed isotopic studies of water across a 10,000 sq mi area that has exhaustively sampled important components of the terrestrial hydrologic cycle (precipitation, groundwater, and surface waters). We leverage the support of volunteers and citizen scientists to crowd source samples for isotopic analysis. The database consists of water samples from 14 precipitation sites, 409 ground water sites and 516 surface water sites across the state of Massachusetts, USA. The results indicate that groundwater isotopic composition ranges from delta O-18 -11 to -4 parts per thousand surface water ranges from delta O-18 -13 to -3.84 parts per thousand and precipitation ranges from delta O-18 -17.88 to -2.89 parts per thousand. On a first order, the small bias of mean groundwater (-8.7 parts per thousand) and surface water (-8.0 parts per thousand) isotopes compared to precipitation delta O-18 (-7.6 parts per thousand) supports that groundwater recharge and surface water storage effects through the hydrologic year impact the isotopic composition of surface and groundwater. While differences are distinct, they are larger than previously reported values, but still suggest more importance of summer precipitation than previously acknowledged. On average seasonal amplitudes of precipitation (2.7 parts per thousand), surface water (1.13 parts per thousand), and groundwater (similar to 0 parts per thousand) of the region demonstrate young water fractions of surface water to be 40% with groundwater similar to 0%. Results demonstrate that mean delta O-18 in precipitation, surface water and groundwaters are more enriched in heavy isotopes in areas near the coast, than the interior and western portion of Massachusetts. The hope is for this dataset to become an important tool for water management and water resource assessment across the region.





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Creative Commons Attribution 4.0 License
This work is licensed under a Creative Commons Attribution 4.0 License.


Massachusetts Water Resources center through the NIWR USGS 104B program [2009MA213G]; Massachusetts Environmental Trust [METFY2018UMAMHERST01]