Water conduction from shallow water tables

does not appear. First page follows. Introduction The phenomenon of the flow of liquids through porous mediums without the application of external force and without complete filling of the pores of the solid with liquid, has long been recognized and studied. It was early recognized that the forces involved are those of adhesion and cohesion, the same as those responsible for the action of liquids in capillary tubes. The term “capillarity” (6), (17)4 has thus come to apply to the flow of liquids through porous mediums. Many analyses (28)-(31) have been made for the purpose of evaluating the capillary forces acting in three-phase systems, such as is the case in moist soil, consisting of solid, liquid, and gas, by assuming spherical solid particles of uniform size and sequence of packing arrangement. While this assumption has presented concepts of value in comprehending the mechanism involved in capillary flow, the size and configuration of the solid and liquid phases are very complex in even the most idealized systems, and become indeterminate when applied to natural bodies such as soil. The capillary potential concept, introduced by Buckingham (6) in 1907, assumed a capillary force field generated by the attraction of moist soil for water. He defined a capillary potential, the gradient of which is equal in magnitude to the capillary force.