Desenvolvimento dum sistema de rega automático, autónomo e adaptativo - Estudo comparativo de cinco métodos para o cálculo da ETo

In order to develop an automatic irrigation system, a set of five different methods for calculating reference evapotranspiration are studied and calibrated (Priestley-Taylor, Makkink, Hargreaves, Turc, Jensen-Haise). These methods use temperature, T, and solar radiation, Rs, to calculate evapotranspiration. Evapotranspiration is calculated for all the days of the 2005/06 hidrological year at the Divor meteorological station. The results are compared to, and calibrated against, the Penman-Monteith method. The best results are obtained by the Priestley-Taylor and Jensen-Haise methods. Calibration coefficients are also calculated for all five methods, so that the results can be as close as possible to those produced by the PenmanMonteith method. Palavras-chave: Penman-Monteith, Priestley-Taylor, Makkink, Hargreaves, Turc, Jensen-Haise 1. INTRODUCAO