Simultaneous estimation of soil hydraulic and solute transport parameters from transient in®ltration experiments

Estimation of soil hydraulic and solute transport parameters is important to provide input parameters for numerical models simulating transient water ̄ow and solute transport in the vadose zone. The Levenberg±Marquardt optimization algorithm in combination with the HYDRUS-1D numerical code was used to inversely estimate unsaturated soil-hydraulic and solute transport parameters from transient matric pressure head, apparent electrical conductivity, and e‚uent ̄ux measurements. A 30 cm long soil column with an internal diameter of 5 cm was used for in®ltration experiments in a coarse-textured soil. In®ltration experiments were carried out with both increasing and decreasing solute concentrations following a sudden increase in the in®ltration rate. Matric pressure heads and solute concentrations were measured using automated mini-tensiometers and four-electrode sensors, respectively. The simultaneous estimation results were compared with independently measured soil water retention, unsaturated hydraulic conductivity, and solute dispersion data obtained from steady-state water ̄ow experiments. The optimized values corresponded well with those measured independently within the range of experimental data. The information contained in the apparent electrical conductivity (which integrates information about both water ̄ow and solute transport) proved to be very useful for the simultaneous estimation of soil hydraulic and solute transport parameters. Ó 2000 Elsevier Science Ltd. All rights reserved.