In this paper, a problem involving time-dependent water flow in a homogeneous soil is considered. The problem involves water infiltration from periodic identical trapezoidal channels. A governing equation of the problem is the Richard’s equation, which can be studied more conveniently by transforming the equation to a Helmholtz equation using the Kirchhoff transformation with dimensionless variables and a Laplace’s transform. A dual reciprocity boundary element method (DRBEM) is employed to solve the Helmholtz equation numerically. Results obtained are found to be physically reasonable.