B.J. Andraski

Fundamental understanding of hydrologic conditions and transport processes is critical to water-resource and waste management decisions. Studies at the Amargosa Desert Research Site near Beatty, Nevada show that the coupled flow of heat and water (as gas and liquid) needs to be considered in the conceptualization and evaluation of water movement. Liquid fluxes typically are small, but may exceed 100 mm/d in near-surface soil during infiltration events. Below 1 m, calculated thermal-vapor fluxes of 0.01 to 0.001 mm/d exceed the isothermal fluxes by 100 to >10,000 times. Relative to simulations of water and heat flow using the common Brooks-Corey water-retention function, simulations using the Rossi-Nimmo (RN) full-theta-range function improved prediction of water potentials in near-surface soil, particularly under dry conditions, and improved prediction of temperatures throughout the soil profile. Such improvements can be important for calculation of water fluxes in desert soils and deep unsaturated zones. Sensitivity analysis showed that prescribed changes in the RN and vapor-conductivity functions, however, were not always sufficient to reproduce the dynamics of the field system. Discrepancies between measured and modeled results highlight uncertainties in the characterization and understanding of arid-site transport processes.

This abstract was published in Annual Meetings Abstracts, American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Charlotte, North Carolina, October 21-25, 2001, CD-ROM computer file.