A POTENTIAL EVAPOTRANSPIRATION PREDICTION SUBMODEL FOR MULTIDIMENSIONAL WATER-FLOW IN SOILS

Net radiation and potential evapotranspiration are required input para meters for most crop growth models and multi-dimensional water flow an d solute transport models. Field estimation of these parameters is a l engthy and costly process. An analytical evapotranspiration submodel ( ETM) was developed as a simple means to predict daily extraterrestrial radiation, clear sky solar radiation, net radiation, pan evaporation and potential evapotranspiration from a minimal set of weather data: m inimum and maximum daily temperatures, latitude and altitude of the lo cation, ratio of actual to maximum possible sunshine hours, day of the year, and reflectivity of the surface. Such weather data sets are rea dily available for most locations and do not require intensive data co llection. Simulations using the ETM model compared favorably to publis hed measured data for these variables. ETM is a compact analytical mod el that offers rapid long-term estimates of weather data. It can easil y serve as a submodel of multi-dimensional models for water flow and s olute transport in soils.