Numerical model of water flow in a fractured basalt vadose zone: Box Canyon site, Idaho

A numerical model of a fractured basalt vadose zone has been developed on t he basis of the conceptual model described by Faybishenko et al. [this issu e]. The model has been used to simulate a ponded infiltration test in order to investigate infiltration through partially saturated fractured basalt. A key question addressed is how the fracture pattern geometry and fracture connectivity within a single basalt Row of the Snake River Plain basalt aff ect water infiltration. The two-dimensional numerical model extends from th e ground surface to a perched water body 20 m below and uses an unconventio nal quasi-deterministic approach with explicit but highly simplified repres entation of major fractures and other important hydrogeologic features. The model adequately reproduces the majority of the field observation and prov ides insights into the infiltration process that cannot be obtained by data collection alone, demonstrating its value as a component of field studies.