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This article in SSSAJ

  1. Vol. 49 No. 6, p. 1581-1583
     
    Received: Aug 20, 1984
    Published: Nov, 1985


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doi:10.2136/sssaj1985.03615995004900060050x

Point and Line Infiltration—Calculation of the Wetted Soil Surface1

  1. A. W. Warrick2

Abstract

Abstract

For water introduced at a point on the soil surface a finite-sized area becomes wetted which is not exceeded for large times. Similarly, a wetted strip develops parallel to a surface line source. In this paper, relationships are derived to provide the limiting (steady-state) extent of these wetted areas. The quasi-linear assumption necessary for solution is that the unsaturated conductivity K is Ko exp(αh) with h the pressure head (matric potential as a length) and Ko and α constants. Results for the area around a point is in near agreement with Wooding's (1968) approximation Ko2q = (πα2ro2 + 4αro)−1 for a slightly different surface boundary condition (ro is the wetted radius and q is the volume of discharge per unit time). For the strip the dimensionless quantity KoqL = (3.96 αxo/2 + 0.721)−1 is a valid approximation for αxo/2 <5 where qL is the rate of discharge per unit length and 2xo the wetted width. For larger αxo/2 the simpler one-dimensional relationship KoqL = 1/(2αxo) suffices. The results are relevant with respect to trickle (drip) irrigation.

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