Field evidence for density-driven free convection, a potentially important groundwater transport process, has been examined at Padre Island National Seashore to determine if this phenomenon can develop under natural environmental conditions. Hitherto, this process had not been conclusively detected or measured in field scale hydrogeology. Field methods, including nested monitoring wells and time-lapse 3-D resistivity surveys, reveal evidence of variable-density groundwater flow in the wind-tidal flats. Evaporative concentration of groundwater near the water table resulted in unstable inverted density gradients, reduced groundwater levels, and reduced hydraulic gradients. These factors allowed plumes of dense fluid to migrate downward into less dense fluid which were observed in monitoring wells and 3-D resistivity surveys. This shows that the development and flow of variable-density fluids in groundwater can be detected and monitored through field techniques. It demonstrates that the development of density inversions may overcome the dissipating forces of dispersion and diffusion to create a sufficiently large unstable gradient to induce free convection. / text
| Identifer | oai:union.ndltd.org:UTEXAS/oai:repositories.lib.utexas.edu:2152/20403 |
| Date | 24 June 2013 |
| Creators | Stevens, Joel Daniel, 1976- |
| Source Sets | University of Texas |
| Language | English |
| Detected Language | English |
| Format | electronic |
| Rights | Copyright is held by the author. Presentation of this material on the Libraries' web site by University Libraries, The University of Texas at Austin was made possible under a limited license grant from the author who has retained all copyrights in the works. |
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