Accession Number : AD0688177

Title :   SOIL-WATER MOVEMENT IN RELATION TO MEASURED PHYSICAL PROPERTIES.

Descriptive Note : Final rept. Jul 66-Jun 68,

Corporate Author : CALIFORNIA UNIV DAVIS DEPT OF WATER SCIENCE AND ENGINEERING

Personal Author(s) : Nielsen,Donald R.

Report Date : JUL 1968

Pagination or Media Count : 80

Abstract : A parameter for the description of water transport in the presence of temperature gradients using diffusion theory or irreversible thermodynamics is the isothermal soil-water diffusivity. A laboratory method was developed for calculating isothermal soil-water diffusivity values for soils at 5 to 15 volume percent water. Diffusivity values were obtained easily and compared favorably with those of previous investigators. The redistribution of soil water within columns of Columbia fine sandy loam in response to imposed temperature gradients was analyzed. Transient water content distributions were monitored with gamma-radiation attenuation while those of soil temperature were recorded with the aid of thermistors. Values of net water flux were examined in light of Fick's law, a diffusion theory proposed by Philip and de Vries, and an irreversible thermodynamic theory used by Taylor and Cary. Fick's law consistently underpredicted the observed water fluxes while the Philip-de Vries theory yielded acceptable values. Predictions of water flux based upon the Taylor-Cary theory were not acceptable by an order of magnitude. An intensive field investigation was conducted to measure and predict the soil temperature behavior during and following infiltration. A simplified mathematical model was used to predict temperature changes from the soil surface to a depth of 2 meters. (Author)

Descriptors :   (*SOILS, TRANSPORT PROPERTIES), (*WATER, DIFFUSION), FLOW FIELDS, TEMPERATURE, DRYING, SAND, GAMMA COUNTERS, RADIATION MONITORS, THERMISTORS, HEAT FLUX, THERMODYNAMICS, MATHEMATICAL MODELS, SURFACE PROPERTIES

Subject Categories : Hydrology, Limnology and Potamology
      Soil Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE