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Dissertation/Thesis Abstract

Isotopic flow determination and geochemical and geomorphic impacts on vegetation cover for western North American springs ecosystems
by Schaller, Elizabeth M., M.S., Northern Arizona University, 2013, 131; 1537810
Abstract (Summary)

Recharge areas for most springs are rarely known because they can be sourced from proximal, shallow, atmospheric sources or long-travelled, deep, regional aquifers and alteration along the flow path is common. Stable isotopic (18O and 2H) geochemistry of springs water can provide indications of relative flow path distance. Locally sourced springs generally have an isotopic signature similar to the isotopic values of local precipitation for that region and elevation. Springs with a different isotopic composition than local meteoric inputs likely have non-local recharge, representing a regional source. Exceptions to this rule include springs in karst terrain, geothermal locations, or travertine-rich groundwater systems, where other physical or geochemical processes influence the isotopic signature of the water. In this study, we tested local vs. regional sourcing using springs isotopic data from regional studies across Western North America in Arizona, Nevada, and Alberta. These regional study sites included the Basin and Range, Transition Zone, Colorado Plateau, Cordillera, Interior Plains physiographic regions, and lowland to montane aquifers. The combination of location-specific physical data with stable isotopic groundwater data provides an effective method for flow path determination at springs with similar flow and chemistry. Springs from Arizona were found to be a mix of regional and local recharge, those from Nevada were locally sourced, and Alberta's springs are generally sourced from regional flow systems.

Springs provide a truly unique ecosystem where groundwater first daylights, mixes with surface waters, and both plants and animals find refuge. Variability of springs type (the springs geomorphic properties) can have profound effects on all aspects of a groundwater spring. Water chemistry may exert significant changes on vegetation, which in turn modify the springs ecology. Changes in vegetation composition and density can also change erosion rates and channel morphology, thereby altering geomorphology. Analyses of data from southern Nevada and Alberta, Canada housed in an extensive springs database of western North America were interpreted to determine the interconnectedness of geochemistry, geomorphology, and vegetation cover. Using various statistical techniques, the opposite variables were significant in the two field areas. In the Spring Mountains the highest elevation clusters had the highest plant species diversity and the fewest spheres of discharge. In Alberta the clusters with average elevation, neither highest nor lowest, were the groups with the highest plant species diversity and most variability in geomorphic surface types.

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Indexing (document details)
Advisor: Springer, Abraham E.
Commitee: Cline, Michael L., Stevens, Lawrence E.
School: Northern Arizona University
Department: School of Earth Sciences and Environmental Sustainability:
School Location: United States -- Arizona
Source: MAI 51/06M(E), Masters Abstracts International
Subjects: Geology, Hydrologic sciences, Geomorphology
Keywords: Groundwater, Isotopes, Precipitation, Vegetation
Publication Number: 1537810
ISBN: 978-1-303-09689-1
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