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An Algorithm for the Calculation of Drain Spacings For Layered Soils

Inst. of Agrophysics, Polish Academy of Sciences, Lublin, Poland

R. R. Van der Ploeg^*

Institut für Bodenkunde und Standortslehre (310), Universität Hohenheim, Emil-Wolff-Strasse 27, Postfach 700562, D-7000 Stuttgart 70, Federal Republic of Germany

Don Kirkham

Dep. of Agronomy, Iowa State Univ., Ames, IA 50011

* Corresponding author.

ABSTRACT

An algorithm is presented with which the tile drain spacing for layered soils can be calculated. The algorithm also works for homogeneous soils, as a special case of layered soils. The algorithm applies to potential flow theory developed for steady-state conditions in horizontal soils. A small programmable desk-top computer suffices for necessary computations. The algorithm can provide results to four or more significant figures for a wide range of design parameters. An example table of spacing values is given for hydraulic conductivity ratios of the upper to the lower soil layer of 50, 10, 5, 2, 1, 1/2, 1/5, 1/10, and 1/50. The results agree with earlier nomograph results but are more precise. The earlier nomographs can provide starting values for the algorithm, but such starting values are not necessary.

Contribution from the Inst. of Soil Science and Plant Environment, Hohenheime Univ., Stuttgart, West Germany, and the Dep. of Agronomy, Iowa State Univ. Iowa Agric. and Home Economics Exp. Stn. Journal Paper no. J-12603. Project no. 2556.

Received for publication March 23, 1987.