Comparison of the Glover Solution with the Simultaneous‐Equations Approach for Measuring Hydraulic Conductivity

The Glover solution and the simultaneous‐equations approach have been suggested for determining the saturated hydraulic conductivity ( K s ) of the vadose zone by the constant‐head well permeameter technique. The objective of this paper is to examine the two procedures and discuss the uncertainty associated with calculating K s by the simultaneous‐equations approach (referred to as K fs ) as compared with using the Glover solution. Two flow regions are identified with the constant heights of water, H 1 and H 2 ( H 2 > H 1 ), at the bottom of an auger hole of radius r during measurements of steady state flow rates, Q 1 and Q 2 . The K s 's over the distances H 1 (lower region), H 2 – H 1 (upper region), and H 2 (entire wetted zone) at the bottom of the hole are designated as K sl , K su , and K sc , respectively. Using the Glover solution for calculating K sl and K sc for a homogeneous and isotropic medium, an equation is developed for calculating K su based on Q 1 , H 1 , Q 2 , H 2 , and r . This equation is found to be very similar to the equation for calculating K fs by simultaneous‐equations approach. It is shown that K sl > K sc whenever the K fs value is negative. Conversely, the matric flux potential calculated by the simultaneous‐equations approach (φ m ) is negative only when K sc > K sl . This is significant because, in the simultaneous‐equations approach, the K fs value will not be acceptable when φ m is negative. The Glover solution (i.e., equation to calculate K sc or K sl ) is applicable to both homogeneous and heterogeneous soils and does not yield a negative value, whereas the simultaneous‐equations approach can only yield reliable results for homogeneous and isotropic media.