Maximum height of capillary rise starting with soil at capillary saturation

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Introduction

The height to which water will be lifted through a soil by film forces, commonly designated as “capillary rise,” is an important factor in many phases of agricultural practice, particularly in determining the depth at which the ground water table should be maintained in order to prevent evaporation from the surface.

In most experiments heretofore reported, the capillary rise has been determined by starting with the soil in an air-dry. condition and usually in tubes of relatively small diameter.⁽³⁾ The experiments of Hilgard⁽¹⁾ have generally been quoted to show a maximum rise of 122 inches in the silt separate with less rise in all the other separates, while the work of Linde and Dupre⁽²⁾ shows that under ideal conditions, where friction of flow through the soil is eliminated, the total height may reach nearly to thirty feet!

Since most soils in agricultural use are frequently or occasionally wetted to the water table by rain or by irrigation, it was felt that to properly measure the maximum possible “capillary rise” under conditions simulating those in the field, the soils should be started at or near capillary saturation, and the ability of the soil to raise water be measured by the amounts removed from a ground-water reservoir and evaporated from the surface.