Estimation of Equilibrium Convection-Dispersion Equation Parameters from Soil Hydraulic Data

Mahmoodi, Mohammad Ali; Shorafa, Mahdi; Homaei, Mahdi; Liaghat, Abdolmajid; Abbasi, Fariborz

doi:10.22059/ijswr.2012.24352

Estimation of Equilibrium Convection-Dispersion Equation Parameters from Soil Hydraulic Data

Authors

Mohammad Ali Mahmoodi

Mahdi Shorafa

Mahdi Homaei

Abdolmajid Liaghat

Fariborz Abbasi

10.22059/ijswr.2012.24352

Abstract

Dispersivity (?) and effective transport porosity (?eff) are input parameters in equilibrium Convection Dispersion Equation (CDE). Normally these parameters are obtained from breakthrough curves by inverse method. However, obtaining breakthrough curves in the field is not often possible in practice. The objective of this study was to estimate ? and feff from soil hydraulic data. For this purpose a conceptual model was developed which describes the transport of a nonreactive solute based on soil hydraulic properties. Both deterministic and stochastic simulation approaches are made use of. The breakthrough data obtained from the simulations were utilized to estimate transport parameters through inverse method. Results revealed that there was no significant difference between predicted and observed ? at P < 0.05 in stochastic approach. However the procedure tends to over-predict small values of ?, while under-predicting large values of ?, especially in the deterministic approach. The estimates of the effective transport porosity being less than those of total porosity (?), indicated that only a portion of total porosity takes part in solute transport. This procedure can be utilized to estimate ? and ?eff from soil hydraulic properties in each and any scale.

Keywords

Breakthrough curves

Convection-dispersion equation

Parameter Estimation

Soil hydraulic data