Assessment of the SPAW model for semi-arid growing conditions with minimal local calibration

Abstract

The performance of the soil—piant—air—water (SPAW) model, developed in the United States, was assessed using data from a long-term experiment where wheat ( Triticum aestivum L.) was grown on fallow land in the semi-arid zone of Saskatchewan. The input of the model consisted primarily of functions and parameters that were obtained from the literature and which were held constant from year to year; exceptions were the locally measured precipitation and potential evapotranspiration data, as well as the appropriate seeding and harvesting dates. Model predictions of soil water content in the root zone corresponded well with measured values, with an overall root mean square of the difference between the measured and the estimated water content of 1.8 cm. A reasonable separation of the components of actual evapotranspiration was obtained. The possibility of predicting bimodal flow with the model increases its utility with regard to water use and soil fertility studies.