Equivalent Diameter of Simulated Macropore Systems during Saturated Flow

Under natural conditions, soil pore systems that conduct water vary in shape, cross‐sectional area, and continuity. Because of this, it is virtually impossible to predict the flow of water through these pore systems. We conducted an experiment to measure the equivalent spherical diameter, d eq , of simulated nonuniform macropore systems for 11 combinations of lengths of three radii of cylindrical, straight‐walled glass tubing during saturated flow. Also, we wanted to determine if experimental data of d eq of the simulated macropores are described by a derived theoretical equation where d eq is a function of the total length of the three tubes, their individual lengths, and their radii. Three known, uniform‐i.‐d. tubes of differing lengths, of cylindrical, straight‐walled glass, in series configuration were used to simulate to a small degree the geometry of macropores as they occur in the field. Inside diameters were 5.08 (L), 1.88 (M), and 0.94 (S) mm. A constant length of 0.60 m was maintained for the pore system. The d eq values of these non‐uniform pore systems were measured. Flux values were measured at eight hydraulic pressures. Equivalent diameters were calculated using Poiseuille's law from the measured flux. The data points of d eq of the pore system were described well by the derived equation. The experimental saturated hydraulic conductivity ( K sat ) was also well described by a derived function.