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Presenters Notified: November 2012

Program Schedule Posted:November 2012

Abstracts Available: January 2013

17-22 February 2013

Cardenas, M. B., University of Texas at Austin, USA, cardenas@jsg.utexas.edu
Gerecht, K. E., Colorado School of Mines, USA
Markowski, M. S., University of Texas at Austin, USA
Nowinski, J. D., University of Texas at Austin, USA
Sawyer, A. H., University of Kentucky, USA
Swanson, T. E., University of Texas at Austin, USA
Guswa, A. J., Smith College, USA


Daily upstream dam water releases causes the Lower Colorado River (LCR) in Texas to fluctuate by 1.5 m which drives a transition between upward and downward fluid fluxes across the sediment-water interface. Hydraulic and thermal monitoring shows that river-groundwater exchange flux is consistently larger close to and then decreases away from the bank; the hyporheic mixing zone (HZ) is deepest near the bank where fluid residence time is also longest. When the river is high, downward advection of heat from a previous cycles’ warm-water pulse warms the HZ down to 1 m. When the river is lowest, upwelling groundwater cools the HZ. Sixteen transverse 2D electrical resistivity (ER) images taken over one flood cycle captured the dynamic HZ mixing. The HZ is laterally discontinuous and several meters deep. Underneath the HZ was a transitional mixing zone intermittently flushed by mixing river water and deep groundwater; groundwater dominated the deepest areas. Future research should consider and focus on a more thorough understanding of the impacts of dam regulation on the hydrologic, thermal, biogeochemical and ecologic dynamics of rivers and HZs.

Oral presentation

Session #:SS30
Date: 2/20/2013
Time: 17:15