Evapotranspiration forecast and its use in gravity irrigation

Abstract

A relatively simple deterministic model to predict short-term evapotranspiration is proposed. The model is based on the evaporation statistical behavior representation, using a weighted index that considers the trend within a mean yearly period. This index has a seasonal variation that may be estimated over short intervals, by means of empirical equations that may be obtained using the minimum squares correlation technique. Starting with the mean evaporation for short time spans and its relation with the proposed index, evaporation may be predicted for the following period. The known evaporation serves to estimate the evapotranspiration for the crop under study by introducing a crop correction factor. The method is applied to predict evapotranspiration of wheat in Ocotlán, Jalisco, Mexico.