An integrated approach for estimation of van genuchten model parameters in undisturbed and unsaturated soils

Abstract

The hydraulic properties of soil are very important to determine the soil relationship with water. The Soil Hydraulic Properties (SHP) are used to determine the soil water relationship as it is very crucial for estimation of water holding capacity of soil. In real field conditions, most widely used model for soil moisture retention curves is van Genuchten model. The soil samples were taken randomly from five different depths with three replications of each depth. Moreover, two samples at the depth of 5-35cm and 35-155cm were selected for evaluation of integrated approach to find soil characteristic curves. Soil moisture characteristic curves calculated by integral approach were compared with, soil moisture curves measured by pressure plate apparatus, and Soil Plant Air Water (SPAW) hydrology a computer based Model. The accuracy of results were evaluated by determination of Root Mean Square Error (RMSE), Normalize Root Mean Square Error (NRMSE) and Willmott’s index of agreement (£). A good agreement was observed between integrated approach, high-pressure technique and SPAW model results. In case of integrated method versus high-pressure technique the RMSE was 9.51×10-3 for 5-30cm depth and 8.32×10- 3 for 30-155cm depth. The NRMSEs was 6.52 ×10-2 for 5-30cm depth and 6.1×10-2 for 30-155cm depth, similarly £ was 0.881 and 0.893 for both depths 5-30cm and 30-155cm respectively. Regression coefficient (R2 ) for 5-35cm depth for sorptivity (s) and wetting distance (d) were 0.991 and 0.988 respectively and at depth of 35-155cm, R2 for (s) was 0.990 and for wetting distance (d) was 0.994. In case of integrated method versus SPAW hydrology the RMSEs was 1.3×10-2 for 5-30cm depth and 1.15×10-2 for 30-155cm depth. The NRMSEs for was 9.33 ×10-2 for 5-30cm depth and 7.15×10-2 for 30-155cm depth and similarly £ was 0.852 and 0.863 for both depths respectively. Results indicated a good relationship between high-pressure technique, SPAW hydrology results and integral method. However, integrated approach is best approach to determine the soil moisture characteristics curves of undisturbed and unsaturated soils