Analysis of flow along anisotropic fractures in partially saturated media

Potential fast flow paths could exist along fractures and faults below washes or other localized recharge areas. When a finite amount of water percolates downward, the imbibition process will remove water from the fracture into the unsaturated tuff matrix, especially in nonwelded units with large porosity and high sorptivity. The anisotropic characteristics of a fault sample, the flow path distribution, and the matrix imbibition effect on fracture flows are analyzed. For the Paintbrush nonwelded bedded tuff unit, the saturation in the middle of a wash is higher than the values measured in boreholes on the side-slopes. The implications of calculated results for the interpretation of saturation distribution in the wash are discussed.