Technical Abstract: Boron is an element with a narrow range between deficiency and toxicity for plants. Reuse of agricultural drainage waters and treated municipal wastewaters is impaired by the often elevated concentrations of B. Knowledge of the B concentrations in soil solution and transport of B out of the soil, is essential for management of waste waters. Prediction of B concentrations requires consideration of B adsorption and desorption, which are dependent on soil properties and solution composition, especially pH. We first applied a 0.08 mmol B solution to three arid land soils from S California and subsequently leached the soils with a low B solution. The experiment was conducted at pH 6.8 and 8.6. The experimental data compared well with predictions using the UNSATCHEM transport model with the constant capacitance model and prediction of the model constants based on soil properties, without the need for soil specific determinations of B adsorption characteristics. Use of a single generalized set of constants for all soils did provided an equally satisfactory fit to the experimental data