Determination of the equivalent saturated hydraulic conductivity of fractured rock located in the vadose zone

Abstract

A method with which to estimate the equivalent saturated hydraulic conductivity and its associated spatial distribution in fractured rock situated in the vadose zone has been developed. Conductivity is estimated in part from outflow rates, induced by a constant hydraulic head, monitored over three meter intervals in boreholes which are oriented in a manner so as to intersect the major fracture sets of a field site. Outflow rates are monitored by means of a falling-head flowmeter while borehole intervals are isolated with a single inflatable packer. Upon collection of the field data, hydraulic conductivity values are estimated by means of two analytical solutions. The solutions are adapted to meet the special conditions posed by variable borehole orientations and multiple test intervals from existing solutions associated with borehole permeability tests. The developed methodology is subsequently utilized to determine the saturated hydraulic conductivity and the associated spatial variability of fractured tuff located near Superior, Arizona.