Laboratory Comparison of Field Infiltrometers

Three devices for measuring hydraulic conductivity of soil in the field were tested under controlled conditions in the laboratory using three types of media to compare their accuracy and precision: modified Philip-Dunne infiltrometer, double-ring infiltrometer, and minidisk infiltrometer. Accuracy was determined by comparing the hydraulic conductivity values obtained by using these devices with those obtained by reference falling-head tests. Of the three devices, the modified Philip-Dunne infiltrometer had the lowest relative error and the double-ring infiltrometer was the most precise. The minidisk infiltrometer had a higher relative error for the coarsest media, suggesting it is not appropriate for use on coarse sands and gravels. Compared with the double-ring infiltrometer, the modified Philip-Dunne and minidisk infiltrometers require less water and testing time, facilitating more measurements at a given site. The modified Philip-Dunne infiltrometer, however, requires measuring or estimating the initial and final soil moisture content, whereas the minidisk infiltrometer requires the media grain-size distribution to estimate the van Genuchten parameters of the media.