Principles and errors of measuring infiltrability with horizontal soil column and Green-Ampt model

Infiltration is an important component of natural water circulation. A new method was advanced to experimentally measure and theoretically compute the soil infiltrability based on the water/mass balance and the assumption of Green-Ampt distribution of soil moisture content in the infiltrating horizontal soil column. A sandy loamy soil was used to illustrate the experimental method and procedures as well as the algorithms for estimating infiltrability from the experimental data. Comparisons of the cumulative infiltrated water amount as computed with the estimated infiltrability with the total supplied water and that estimated from the actual changes in the moisture contents of the soil column indicate that the relative estimation errors are 11.5% and 15.89% respectively, and the relative error between the actual supplied water volume and water derived from the actual water contents measured in the experiment is only 1.02%, which demonstrates a relatively high accuracy of the method and also the possibility to improve the accuracy of this method. The results show that the method can well conceptually represent the very high initial soil infiltrability compared with the conventional methods. This method is convenient for faster field determination of soil infiltrability with much less water required. It will find its wide applications of future study in this direction.