Some new procedures for numerical solution of variably saturated flow problems

Persistent difficulties that arise in forming numerical solutions of variably saturated flow problems include controlling the stability of the nonlinear equation solvers and devising a reliable, yet efficient, method for determining the positions of seepage surfaces. New techniques for addressing these problems are applied to a subdomain finite element discretization of the governing flow equations. A series of test problems demonstrates that the techniques are reliable and efficient for a wide variety of problems.