SOIL-BASED IRRIGATION AND SALINITY MANAGEMENT MODEL .2. WATER AND SOLUTE MOVEMENT CALCULATIONS

The utility of a new model for irrigation and soil salinity management is based largely on the agreement between measured and predicted water and solute movement in the soil profile. Data suitable for comparison to model calculations is lacking in the literature. We conducted a greenhouse study designed to obtain detailed temporal salt and water distribution data under fluctuating shallow saline water table conditions, and compared simulated and observed data. Our model's calculations for water content and salinity agreed well with the observed distributions. Willmott's d index (a statistical index of agreement between measured and observed data) results ranged from 0.83 to 0.97 (perfect agreement = 1.0). Agreement was improved when potential evapotranspiration (PET) estimates were adjusted for data from individual treatment columns in the greenhouse experiment. The d-index values, following adjustment of PET, increased to 0.94 or higher, indicating the importance of accurate localized PET estimates for optimum model performance.