A Compact Constant‐Head Permeameter for Measuring Saturated Hydraulic Conductivity of the Vadose Zone

Most procedures for determination of saturated hydraulic conductivity ( K s ) of the vadose zone are difficult to perform and time consuming. Recent developments have shown that K s can be determined by the constant‐head well permeameter technique with a few liters of water in less than 30 min using small‐diameter auger holes. A compact constant‐head (CCH) permeameter is designed for maintaining a constant height of water (>5 cm) at the bottom of a 4‐ to 10‐cm‐diam. hole in the unsaturated zone, and measuring the amount of water flowing into the hole. The main unit of the CCH permeameter is used for measuring K s from the soil surface to a depth of 2 m. To determine K s below 2‐m depth a special flow‐measuring reservoir, equipped with a portable pressure transducer, is connected to the device and inserted to the bottom of the hole. The CCH permeameter has a water‐holding capacity of 5 L, can be used on any landscape position without an external support, and can be easily transported in the field. The device has been tested in the laboratory and field, and is capable of delivering a maximum flow rate of 3 × 10 −6 m 3 s −1 .