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Beyond the paired-catchment approach : isotope tracing to illuminate stocks, flows, transit time, and scaling

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dc.contributor.advisor McDonnell, Jeffrey J.
dc.creator Hale, V. Cody
dc.date.accessioned 2012-01-10T21:00:56Z
dc.date.available 2012-01-10T21:00:56Z
dc.date.copyright 2011-12-19
dc.date.issued 2011-12-19
dc.identifier.uri http://hdl.handle.net/1957/26625
dc.description Graduation date: 2012 en_US
dc.description.abstract This dissertation integrates a process-based hydrological investigation with an ongoing paired-catchment study to better understand how forest harvest impacts catchment function at multiple scales. We do this by addressing fundamental questions related to the stocks, flows and transit times of water. Isotope tracers are used within a top-down catchment intercomparison framework to investigate the role of geology in controlling streamwater mean transit time and their scaling relationships with the surrounding landscape. We found that streams draining catchments with permeable bedrock geology at the Drift Creek watershed in the Oregon Coast Range had longer mean transit times than catchments with poorly permeable bedrock at the HJ Andrews Experimental Forest in the Oregon Cascades. We also found that differences in permeability contrasts within the subsurface controlled whether mean transit time scaled with indices of catchment topography (for the poorly permeable bedrock) or with catchment area (for the permeable bedrock). We then investigated the process-reasons for the observed differences in mean transit time ranges and scaling behavior using a detailed, bottom-up approach to characterize subsurface water stores and fluxes. We found that the mean transit times in catchments underlain by permeable bedrock were influenced by multiple subsurface storage pools with different groundwater ages, whereas storage in the poorly permeable catchments was limited to the soil profile and that resulted in quick routing of excess water to the stream at the soil bedrock interface, leading to mean transit times that were closely related to flowpath lengths and gradients. Finally, we examined how and where forest trees interacted with subsurface storage during the growing season using a forest manipulation experiment, where we tested the null hypothesis that near-stream trees alone influenced daily fluctuations in streamflow. We felled trees within this zone for two 2.5 ha basins and combined this with isotopic tracing of tree xylem water to test if water sources utilized by trees actively contributed to summer streamflow. We rejected our null hypotheses and found that diel fluctuations in streamflow were not generated exclusively in the near-stream zone. We were unable to link, isotopically, the water sources trees were utilizing to water that was contributing to streamflow. Our results provide new process-insights to how water is stored, extracted, and discharged from our forested catchments in Western Oregon that will help better explain how forest removal influences streamflow across multiple scales and geological conditions. en_US
dc.language.iso en_US en_US
dc.relation Oregon Explorer en_US
dc.subject catchment hydrology en_US
dc.subject isotope tracers en_US
dc.subject bedrock groundwater en_US
dc.subject mean transit time en_US
dc.subject diel fluctuations en_US
dc.subject.lcsh Watershed hydrology -- Oregon -- Drift Creek Watershed (Drift Creek Wilderness-Alsea River Estuary) en_US
dc.subject.lcsh Watershed hydrology -- Oregon -- H.J. Andrews Experimental Forest en_US
dc.subject.lcsh Shields (Geology) -- Oregon -- Drift Creek Watershed (Drift Creek Wilderness-Alsea River Estuary) en_US
dc.subject.lcsh Shields (Geology) -- Oregon -- H.J. Andrews Experimental Forest en_US
dc.subject.lcsh Logging -- Environmental aspects -- Oregon -- Drift Creek Watershed (Drift Creek Wilderness-Alsea River Estuary) en_US
dc.subject.lcsh Logging -- Environmental aspects -- Oregon -- H.J. Andrews Experimental Forest en_US
dc.subject.lcsh Forest influences -- Oregon -- Drift Creek Watershed (Drift Creek Wilderness-Alsea River Estuary) en_US
dc.subject.lcsh Forest influences -- Oregon -- H.J. Andrews Experimental Forest en_US
dc.subject.lcsh Forest hydrology -- Oregon -- Drift Creek Watershed (Drift Creek Wilderness-Alsea River Estuary)
dc.subject.lcsh Forest hydrology -- Oregon -- H.J. Andrews Experimental Forest
dc.title Beyond the paired-catchment approach : isotope tracing to illuminate stocks, flows, transit time, and scaling en_US
dc.type Thesis/Dissertation en_US
dc.degree.name Doctor of Philosophy (Ph. D.) in Water Resources Science en_US
dc.degree.level Doctoral en_US
dc.degree.discipline Interdisciplinary Studies en_US
dc.degree.grantor Oregon State University en_US
dc.contributor.committeemember Brooks, J. Renee
dc.contributor.committeemember Ice, George G.
dc.contributor.committeemember Skaugset, Arne E.
dc.contributor.committeemember Chan, Samuel
dc.description.peerreview no en_us


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