Practical Estimation Method for Soil Hydraulic Properties Based on Observed Data in Short-term Experiments Conducted in a Foreign Field

摘要

This study investigated a practical method to estimate soil hydraulic properties based on observed data in existent experiments conducted in a foreign field for short-term stays. This method involved a series of procedures composed of laboratory and in-situ experiments and the inverse estimation of soil hydraulic parameters as results. The laboratory experiments included a falling-head method for the saturated hydraulic conductivity and a one-step outflow experiment. The in-situ experiment was an irrigation-drainage experiment. The inverse estimation technique combined a one-dimensional numerical solution of the Richards equation with Marquartdt-Levenberg optimization. In this paper, this method was applied to a loess field in a semi-arid region inChina to evaluate its effectiveness. These experiments were conducted using portable apparatuses without external power supplies. The inverse approach to the one-step experiment was performed to determine soil hydraulic parameters. The estimations of cumulative outflow using the identified parameters corresponded to the observations. Based on the results, simulations for the in-situ experiment were conducted under three scenarios that changed the number of parameters determined by the inverse approach.The scenario identifying the twelve parameters successfully determined appropriate soil hydraulic parameters under field conditions. The bulk density observed in the field gave good outlines for selecting the parameters for the inverse approach. A minimum of seven to ten days is needed to obtain the essential information for this method, which is one practical technique to comparatively easily estimate appropriate soil hydraulic properties for foreign fields.