Estimation of Soil Water Retention Curve by Measuring Drainable Porosity in Soil Column

One of the most important properties of soil is hydraulic characteristic، which contains saturated soil hydraulic conductivity and parameters of soil water retention curve (SWRC). These characteristics have various applications in soil and water science thus their estimate is so important. In this work، soil water retention curve was estimated by using data obtained from drainable porosity test in soil column by inverse method، and also given moisture content in certain soil water potentials equal to 1. 5 MPa. The experiment was conducted in two replications for Daneshkadeh soil series (clay loam). Parameters αv، nv and θr obtained from optimization were 2. 37، 1. 24 and 00. 0 for the first replication and 1. 77، 1. 26 and 00. 0 for the second replication، respectively. The criterion NRMSE was used to quantify estimated soil moisture. It was 4. 1% and 2. 3% in the first and second replication، respectively. Results showed that drainable porosity experiment is a suitable method to determine Van Genuchten (1980) equation parameters in the region