INDEPENDENT CALIBRATION OF A MECHANISTIC-STOCHASTIC MODEL FOR FIELD-SCALE SOLUTE TRANSPORT UNDER FLOOD IRRIGATION

The model assumes that the pore water velocity varies horizontally across the field but is uniform in the vertical direction. Explicit expressions for chemical diffusion and hydrodynamic dispersion are not included in the model. Instead, horizontal variations in the velocity serve to disperse the solute when measured on a field wide basis. The model requires knowledge of the probability density function for the velocity and estimates of the function parameters. These parameters were estimated from variations in infiltration rates measured within 63 ring infiltrometers and from water retention data. Model simulations of Br- leaching and agreed well with most measured data for both position of the tracer peak and the degree of solute spreading.