Document Type


Date of Degree Completion

Summer 2017

Degree Name

Master of Science (MS)


Geological Sciences

Committee Chair

Carey Gazis

Second Committee Member

Anne Johansen

Third Committee Member

Winston Norrish


The complex bedrock lithologies in the Upper Kittitas County provide an ideal setting for developing isotopic methodology to identify groundwater sources and track flow paths through water-rock interaction. A wide range of 87Sr/86Sr (0.7040 to 0.7068) in surface waters, springs, and groundwater from wells was found, allowing for identification of the individual signatures of lithologic units. Rock leachates from different lithology were compared to water samples to determine a general 87Sr/86Sr signature of the water-rock interaction for that lithology. The signatures identified were systematically lower than their associated waters, but similar enough to identify the expected 87Sr/86Sr of water-rock interaction for most of the units. These signatures can then be compared to unknown waters to identify the source and/or mixing between sources. Using this method, many of the water samples in this study were directly correlated to their sources. The greatest limitations of this method were lithologies that were not geochemically homogenous and overlap in ranges of 87Sr/86Sr for different lithology.