Measuring Soil Hydraulic Properties Using a Cased Borehole Permeameter: Steady Flow Analyses

New, constant‐head permeameter analyses for steady flow in cased boreholes were developed for in situ measurement of field‐saturated hydraulic conductivity ( K fs ) and matric flux potential (ϕ m ) in the vadose zone. The K fs and ϕ m parameters can be determined using calculations based on multiple ponded heads, dual heads, or a single head. The accuracy of the analyses was assessed using HYDRUS‐2D simulations of steady borehole discharge ( Q t ) vs. ponded head ( H ) for specified K fs , ϕ m , soil capillarity (α* = K fs /ϕ m ), and length ( L ) and radius ( a ) of the borehole screen. The multiple‐head and dual‐head calculations provided accurate K fs determinations (≤26% error) for the full range of tested capillarity (0.1 ≤ α* ≤ 14.45 m −1 ), screen radius ( a = 3–7.5 cm), screen length ( L = 0–45 cm), and head ( H = 3–200 cm). The multiple‐head and dual‐head calculations of ϕ m were similarly accurate (≤25% error) for high‐capillarity soils (α* ≤ 1 m −1 ), and for L / a ≤ 1 in moderate‐ to negligible‐capillarity soils (α* ≥ 9 m −1 ). The ϕ m calculations were not accurate, however, in moderate‐ to negligible‐capillarity soils with L / a > 1. The single‐head calculation with α* estimated using soil texture and structure categories was accurate only for K fs determination (≤23% error) in soils with moderate to negligible capillarity. For ϕ m determination, and for K fs determination in high‐capillarity soils, the single‐head calculation requires accurately known α* values. The analyses appear promising for K fs and ϕ m determination in the vadose zone, and further development and testing are ongoing.