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This article in SSSAJ

  1. Vol. 51 No. 2, p. 298-302
     
    Received: Feb 21, 1986
    Published: Mar, 1987


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doi:10.2136/sssaj1987.03615995005100020006x

Field Method for Estimating Hydraulic Conductivity and Matric Potential-water Content Relations1

  1. U. Shani,
  2. R. J. Hanks,
  3. E. Bresler and
  4. C. A. S. Oliveira2

Abstract

Abstract

A method, using “drippers” to estimate the soil hydraulic properties, based on assumed relationships of the hydraulic conductivity (K)-matric head (h), is proposed. The method is based on the observation that when water is applied at a constant rate to a point on the soil surface, a ponded zone is created that approaches a constant area in a short time. Thus, steady-state solutions of the two-dimensional flow equation can be applied. The method is simple to apply and consists of the following steps: (i) Wet the soil from a dripper with several known discharge rates on a relatively level dry soil. A wide range of dripper discharges is needed for a good “spread out” of the data. (ii) Once the borders of the ponded zone are steady, saturated hydraulic conductivity (Ks) and the matric flux function (F) can be evaluated from a regression of flux vs. the reciprocal of the ponded radius. The other soil hydraulic parameters can be derived according to the hydraulic relations assumed. Where an exponential hydraulic conductivity (K)-matric head (h) relation is assumed, these measurements are sufficient so Ks and α (soil parameter) are determined. If the “Brooks-Corey” relations of K-h and water content (θ)-h are assumed, measurements of the saturated and residual water contents (θs, θo) and of the sorptivity (S) are required. The sorptivity is determined by measuring the horizontal wetting front advance from the ponded zone borders as a function of time on the soil surface. The method can be performed on undisturbed field soil. Continuous measurements are possible at about the same site. Measurements of the change of soil water properties, with time, at the soil surface are easily made. A comparison of hydraulic parameters measured and estimated by two other methods for these soils show good agreement with the dripper method.

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