Numerical calculation of saturated‐unsaturated infiltration in a cracked soil

Two‐dimensional infiltration in a soil containing regularly spaced, water‐filled, vertical cracks is determined by a finite difference numerical solution of the saturated‐unsaturated flow equations for selected soil hydraulic characteristics. The equivalent Green‐Ampt model gives results which correspond well with finite difference solutions. Differences in cumulative infiltration and infiltration rates, expressed as percentages of the corresponding finite difference results, typically vary up to about 4%. When the crack spacing‐depth ratio and the magnitude of the moisture potential at the wetting front are both small, calculations predict that wetted tongues moving away from adjacent cracks interact to temporarily enclose an unwetted pocket, an event coinciding with a sudden drop in the infiltration rate and the breakdown of the corresponding Green‐Ampt calculation.