Graduate Thesis Or Dissertation
 

The role of bedrock groundwater in rainfall-runoff response at hillslope and catchment scales

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/rj4306679

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  • Bedrock groundwater dynamics in headwater catchments are poorly understood and poorly characterized. Direct hydrometric measurements have been limited due to the logistical challenges associated with drilling through hard rock in steep, remote and often roadless terrain. Here we develop and use an inexpensive, portable bedrock drilling system to explore bedrock groundwater dynamics aimed at quantifying bedrock groundwater contributions to hillslope flow and catchment runoff. We present results from Watershed 10 (WS10) at the HJ Andrews Experimental Forest in Oregon and at the Maimai M8 research catchment in New Zealand. WS10 is underlain by weathered and fractured tuff and breccias, while Maimai is underlain by a moderately weathered conglomerate composed of clasts of sandstone, granite and schist in a claysand matrix. Analysis of bedrock groundwater levels at Maimai, through a range of flow conditions, showed that the bedrock water table remained below the soil-bedrock interface, suggesting that bedrock groundwater has minimal direct contributions to hillslope runoff. However, groundwater levels did respond significantly to storm events indicating that there is a direct connection between soil water and the underlying bedrock aquifer. WS10 groundwater dynamics were dominated by fracture flow. Preliminary findings show a highly fractured and transmissive region within the upper 1 meter of bedrock that acts as a corridor for rapid lateral subsurface stormflow and lateral discharge. The interaction of subsurface storm flow within bedrock has implications for hillslope response, mean residence time and solute transport. This research shows bedrock groundwater to be an extremely dynamic component of the hillslope hydrological system and comparative analysis outlines the potential range of hydrological and geological controls on runoff generation in headwater catchments
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file details GabrielliChrisP2011.pdf 2017-08-02 Pubblico Scaricare