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This article in SSSAJ

  1. Vol. 40 No. 5, p. 756-761
     
    Received: Jan 21, 1976
    Published: Sept, 1976


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doi:10.2136/sssaj1976.03615995004000050038x

Prediction of Evaporation from Columns of Soil During Alternate Periods of Wetting and Drying1

  1. W. J. Staple2

Abstract

Abstract

This analysis was undertaken to test certain approximations in using finite difference methods to compute evaporation and soil water conservation. Analysis of four evaporation experiments showed that water movement in Wood Mountain clay loam was sufficiently repeatable during wetting and drying to permit computation of evaporation losses on the basis of predetermined soil properties. The experiments involved evaporation after the following treatments: (i) infiltration penetrating partway down columns of air-dry soil; (ii) infiltration and 7 days' redistribution; (iii) treatment (ii) plus additional infiltration; and, (iv) repeated infiltration applied at different stages of initial drying.

In computing evaporation the Richards and Dalton flow equations were used with soil and atmospheric parameters. Temperature gradients in the soil were neglected. Hydraulic conductivity of the surface layers of soil were adjusted empirically to estimate combined liquid and vapor movement and to correct for disruptive effects such as dispersion, air blockage, and swelling near the surface. The independent domain theory was used to estimate the influence of hysteresis on capillary pressures during alternate wetting and drying. Agreement between measured and computed evaporation was satisfactory following infiltration except when water was added after > 7 days' evaporation.

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