This program was developed at the USDA-ARS Conservation and Production Research Laboratory, Bushland, Texas for training and research purposes. It uses the ASCE Standardized Reference Evapotranspiration (ET) Equation for calculating grass and alfalfa reference ET at hourly and daily time steps. Users have the option of using a single set or time series weather data to calculate reference ET. Daily reference ET is calculated by summing up hourly ET values for a given day. Therefore, daily ET calculations require continuous data. Please see the bottom of this page for input and output format for time series weather data.