Water movement in a finite layer:Influence of gravity for constant water content at the surface

Abstract

The flow of water in a finite soil layer is analyzed with gravity, extending an earlier non-gravitational theory. Analytical approximations are obtained to predict the outflow at the lower surface when the potentials at the upper and lower surfaces are fixed. The accuracy of the predictions is checked by comparison with numerical simulations. The solution should be of importance to infer soil properties from outflow measurements in laboratory experiments. The time when outflow first begins and the steady state flow rate are especially useful for that purpose.