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Cardenas, M. B., University of Texas at Austin, Austin, USA, cardenas@jsg.utexas.edu
Sawyer, A. H., University of Delaware, Newark, USA
Gerecht, K. E., Pennsyvlania State University, University Park, USA
Markowski, M. S., University of Texas at Austin, Austin, USA
Francis, B. A., University of Texas at Austin, Austin, USA
Francis, L. K., University of Texas at Austin, Austin, USA
Swanson, T. E., University of Texas at Austin, Austin, USA
Nowinski, J. D., University of Texas at Austin, Austin, USA
Guswa, A. J., Smith College, Northampton, USA

GROUNDWATER-SURFACE WATER INTERACTIONS IN A REGULATED RIVER

Most major rivers have been dammed for societal benefits. In the USA, all watersheds larger than 2000 km2 have dams. We investigated how regular discharges from dams control downstream groundwater-surface water interactions and the hydraulic, thermal and chemical regimes of hyporheic and riparian zones. The study site at the Lower Colorado River (LCR) near Austin, Texas, USA has a mean discharge of 70 m3/s. Observations of hydraulic heads, temperature and electrical resistivity show that 1-2 m daily stage fluctuations cause very large fluid fluxes between the river and its hyporheic and riparian zones which are also accompanied by pronounced heat and solute advection. The LCR, normally a gaining river, now has an extensive but rapidly flushed hyporheic zone where fluids and solutes have short residence times. Therefore, the conceptual model for hyporheic zone functions needs to be updated when applied to regulated rivers. Further, altered groundwater-surface water interactions in the riparian and hyporheic zones of regulated rivers are expected to integrate and ultimately affect downstream delivery of solutes and heat.

Session #:SS03
Date: 7/10/2012
Time: 16:00