Buffer Index Effects on Hydraulic Conductivity Measurements Using Numerical Simulations of Double‐Ring Infiltration

Abstract

The double‐ring infiltrometer is widely used to measure soil saturated hydraulic conductivity in the field. Both the inner ring size and outer ring size (two factors in the buffer index) of an infiltrometer affect the measurements of saturated hydraulic conductivity. Few systematic studies have been conducted to investigate the combined effects of the inner and outer ring sizes of a double‐ring infiltrometer on the measurements of field saturated hydraulic conductivity. A total of 7224 numerical simulations were conducted to investigate the optimum combination of inner and outer ring sizes for reliable saturated hydraulic conductivity measurements by using 24 infiltrometers with six inner ring diameters (10, 20, 40, 80, 120, and 200 cm) and, for each ring diameter, four buffer indices (b = 0.2, 0.33, 0.5, and 0.71). Results demonstrated that the inner ring size is a more important factor to be considered than the buffer index itself (or the outer ring size) in practice, and a larger inner ring diameter assembled with an outer ring (in most cases, with diameter ≥80 cm and b ≥ 0.33) is recommended to obtain reliable in situ measurement of soil field saturated hydraulic conductivity.