ESTIMATING STEADY INFILTRATION-RATE TIMES FOR INFILTROMETERS AND PERMEAMETERS

In the in situ determination of hydraulic conductivity most procedures are based on a close attainment of steady state infiltration. The accuracy of the measurement is therefore dependent on both the degree to which steady state flow is attained and the validity of the assumptions in the analysis procedure. Several approximate analytical solutions of one‐dimensional and three‐dimensional flow provide reasonable estimates of both transient and steady state infiltration compared to the corresponding numerical solutions. Three‐dimensional infiltration initially approaches steady state flow much faster than one‐dimensional infiltration, but at some point close to steady flow and dependent on soil properties, one‐dimensional infiltration approaches steady state faster. Some practical answers are supplied on the time required to reach reasonable estimates of steady state flow, the amount of water used, and the distance to the wetting front for a range of soil properties. Copyright 1990 by the American Geophysical Union.