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WATER RESOURCES RESEARCH, VOL. 39, NO. 7, 1179, doi:10.1029/2002WR001604, 2003

Variations in flow and transport in thick desert vadose zones in response to paleoclimatic forcing (0–90 kyr): Field measurements, modeling, and uncertainties

Bridget R. Scanlon

Bureau of Economic Geology, Jackson School of Geosciences, University of Texas at Austin, Austin, Texas, USA


Kelley Keese

Bureau of Economic Geology, Jackson School of Geosciences, University of Texas at Austin, Austin, Texas, USA


Robert C. Reedy

Bureau of Economic Geology, Jackson School of Geosciences, University of Texas at Austin, Austin, Texas, USA


Jirka Simunek

George E. Brown, Jr., Salinity Laboratory, Riverside, California, USA


Brian J. Andraski

U.S. Geological Survey, Carson City, Nevada, USA


Abstract

An understanding of unsaturated flow and potential recharge in interdrainage semiarid and arid regions is critical for quantification of water resources and contaminant transport. We evaluated system response to paleoclimatic forcing using water potential and Cl profiles and modeling of nonisothermal liquid and vapor flow and Cl transport at semiarid (High Plains, Texas) and arid (Chihuahuan Desert, Texas; Amargosa Desert, Nevada) sites. Infiltration in response to current climatic forcing is restricted to the shallow (∼0.3–3 m) subsurface. Subsurface Cl accumulations correspond to time periods of 9–90 kyr. Bulge-shaped Cl profiles generally represent accumulation during the Holocene (9–16 kyr). Lower Cl concentrations at depth reflect higher water fluxes (0.04–8.4 mm/yr) during the Pleistocene and earlier times. Low water potentials and upward gradients indicate current drying conditions. Nonisothermal liquid and vapor flow simulations indicate that upward flow for at least 1–2 kyr in the High Plains and for 12–16 kyr at the Chihuahuan and Amargosa desert sites is required to reproduce measured upward water potential gradients and that recharge is negligible (<0.1 mm/yr) in these interdrainage areas.

Received 23 July 2002; accepted 31 March 2003; published 10 July 2003.

Index Terms: 1809 Hydrology: Desertification; 1815 Hydrology: Erosion and sedimentation; 1833 Hydrology: Hydroclimatology.

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Citation: Scanlon, B. R., K. Keese, R. C. Reedy, J. Simunek, and B. J. Andraski (2003), Variations in flow and transport in thick desert vadose zones in response to paleoclimatic forcing (0–90 kyr): Field measurements, modeling, and uncertainties, Water Resour. Res., 39(7), 1179, doi:10.1029/2002WR001604.